Showing 1–50 of 96 results for author: Ullom, J

The Simons Observatory: forecasted constraints on primordial gravitational waves with the expanded array of Small Aperture Telescopes

Authors: The Simons Observatory Collaboration, I. Abril-Cabezas, S. Adachi, P. Ade, A. E. Adler, P. Agrawal, J. Aguirre, S. Aiola, T. Alford, A. Ali, D. Alonso, M. A. Alvarez, R. An, M. Aravena, K. Arnold, P. Ashton, F. Astori, Z. Atkins, J. Austermann, S. Azzoni, C. Baccigalupi, D. Baker, R. Balafendiev, A. Baleato Lizancos, D. Barron , et al. (457 additional authors not shown)

Abstract: We present updated forecasts for the scientific performance of the degree-scale (0.5 deg FWHM at 93 GHz), deep-field survey to be conducted by the Simons Observatory (SO). By 2027, the SO Small Aperture Telescope (SAT) complement will be doubled from three to six telescopes, including a doubling of the detector count in the 93 GHz and 145 GHz channels to 48,160 detectors. Combined with a planned e… ▽ More We present updated forecasts for the scientific performance of the degree-scale (0.5 deg FWHM at 93 GHz), deep-field survey to be conducted by the Simons Observatory (SO). By 2027, the SO Small Aperture Telescope (SAT) complement will be doubled from three to six telescopes, including a doubling of the detector count in the 93 GHz and 145 GHz channels to 48,160 detectors. Combined with a planned extension of the survey duration to 2035, this expansion will significantly enhance SO's search for a $B$-mode signal in the polarisation of the cosmic microwave background, a potential signature of gravitational waves produced in the very early Universe. Assuming a $1/f$ noise model with knee multipole $\ell_{\rm knee} = 50$ and a moderately complex model for Galactic foregrounds, we forecast a $1σ$ (or 68% confidence level) constraint on the tensor-to-scalar ratio $r$ of $σ_r = 1.2\times10^{-3}$, assuming no primordial $B$-modes are present. This forecast assumes that 70% of the $B$-mode lensing signal can ultimately be removed using high resolution observations from the SO Large Aperture Telescope (LAT) and overlapping large-scale structure surveys. For more optimistic assumptions regarding foregrounds and noise, and assuming the same level of delensing, this forecast constraint improves to $σ_r = 7\times10^{-4}$. These forecasts represent a major improvement in SO's constraining power, being a factor of around 2.5 times better than what could be achieved with the originally planned campaign, which assumed the existing three SATs would conduct a five-year survey. △ Less

Submitted 17 December, 2025; originally announced December 2025.

Comments: 15 pages (excluding front matter), 4 figures, for submission to JCAP

Development of Silicon Micromachined Waveguide Filter-Banks for On-Chip Spectrometers

Authors: Matthew A. Koc, Jason Austermann, James Beall, Johannes Hubmayr, Joel N. Ullom, Michael Vissers, Jordan Wheeler

Abstract: Development of high-speed, spatial-mapping spectrometers in the millimeter and far-infrared frequencies would enable entirely new research avenues in astronomy and cosmology. An "on-chip" spectrometer is one such technology that could enable Line Intensity Mapping. Recent work has shown the promise of high-speed imaging; however, a limiting factor is that many of these devices suffer from low opti… ▽ More Development of high-speed, spatial-mapping spectrometers in the millimeter and far-infrared frequencies would enable entirely new research avenues in astronomy and cosmology. An "on-chip" spectrometer is one such technology that could enable Line Intensity Mapping. Recent work has shown the promise of high-speed imaging; however, a limiting factor is that many of these devices suffer from low optical efficiency. Here we present the fabrication of a metalized, Si waveguide filter-bank fabricated using deep reactive ion etching for use in millimeter spectroscopy. Our design simultaneously provides high-density pixel packing, high optical efficiency, high spectral resolution, and is readily compatible with simple and multiplexable MKID arrays. Gold plated test waveguide and filter show excellent match to simulations with a measured resolving power of 263 and a loss quality factor of 1116 at room temperature. The results show promise for extending the measurements to larger, multi-wavelength designs. △ Less

Submitted 4 November, 2025; originally announced November 2025.

Comments: 6 pages, 6 figures, submitted to IEEE Transactions on Applied Superconductivity

Demonstration of a 1820 channel multiplexer for transition-edge sensor bolometers

Authors: J. C. Groh, Z. Ahmed, J. Austermann, J. Beall, D. Daniel, S. M. Duff, S. W. Henderson, J. Hubmayr, R. Lew, M. Link, T. J. Lucas, J. A. B. Mates, M. Silva-Feaver, R. Singh, J. Ullom, L. Vale, J. Van Lanen, M. Vissers, C. Yu

Abstract: The scalability of most transition-edge sensor arrays is limited by the multiplexing technology which combines their signals over a reduced number of wires and amplifiers. In this Letter, we present and demonstrate a multiplexer design optimized for transition-edge sensor bolometers with 1820 sensors per readout unit, a factor of two more than the previous state-of-the-art. The design is optimized… ▽ More The scalability of most transition-edge sensor arrays is limited by the multiplexing technology which combines their signals over a reduced number of wires and amplifiers. In this Letter, we present and demonstrate a multiplexer design optimized for transition-edge sensor bolometers with 1820 sensors per readout unit, a factor of two more than the previous state-of-the-art. The design is optimized for cosmic microwave background imaging applications, and it builds on previous microwave superconducting quantum interference device multiplexers by doubling the available readout bandwidth to the full 4-8 GHz octave. Evaluating the key performance metrics of yield, sensitivity, and crosstalk through laboratory testing, we find an end-to-end operable detector yield of 78%, a typical nearest-neighbor crosstalk amplitude of ~0.4%, and a median white noise level of 83 pA/rtHz due to the multiplexer, corresponding to an estimated contribution of 4% to the total system noise for a ground-based cosmic microwave background telescope. Additionally, we identify a possible path toward reducing resonator loss for future designs with reduced noise. We expect these developments to alleviate the system complexity, cryogenic requirements, and cost of future large arrays of low temperature detectors. △ Less

Submitted 17 October, 2025; v1 submitted 14 July, 2025; originally announced July 2025.

Journal ref: Appl. Phys. Lett. 127, 152602 (2025)

The Atacama Cosmology Telescope: DR6 Constraints on Extended Cosmological Models

Authors: Erminia Calabrese, J. Colin Hill, Hidde T. Jense, Adrien La Posta, Irene Abril-Cabezas, Graeme E. Addison, Peter A. R. Ade, Simone Aiola, Tommy Alford, David Alonso, Mandana Amiri, Rui An, Zachary Atkins, Jason E. Austermann, Eleonora Barbavara, Nicola Barbieri, Nicholas Battaglia, Elia Stefano Battistelli, James A. Beall, Rachel Bean, Ali Beheshti, Benjamin Beringue, Tanay Bhandarkar, Emily Biermann, Boris Bolliet , et al. (147 additional authors not shown)

Abstract: We use new cosmic microwave background (CMB) primary temperature and polarization anisotropy measurements from the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) to test foundational assumptions of the standard cosmological model and set constraints on extensions to it. We derive constraints from the ACT DR6 power spectra alone, as well as in combination with legacy data from Planck. To br… ▽ More We use new cosmic microwave background (CMB) primary temperature and polarization anisotropy measurements from the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) to test foundational assumptions of the standard cosmological model and set constraints on extensions to it. We derive constraints from the ACT DR6 power spectra alone, as well as in combination with legacy data from Planck. To break geometric degeneracies, we include ACT and Planck CMB lensing data and baryon acoustic oscillation data from DESI Year-1, and further add supernovae measurements from Pantheon+ for models that affect the late-time expansion history. We verify the near-scale-invariance (running of the spectral index $d n_s/d\ln k = 0.0062 \pm 0.0052$) and adiabaticity of the primordial perturbations. Neutrino properties are consistent with Standard Model predictions: we find no evidence for new light, relativistic species that are free-streaming ($N_{\rm eff} = 2.86 \pm 0.13$, which combined with external BBN data becomes $N_{\rm eff} = 2.89 \pm 0.11$), for non-zero neutrino masses ($\sum m_ν< 0.082$ eV at 95% CL), or for neutrino self-interactions. We also find no evidence for self-interacting dark radiation ($N_{\rm idr} < 0.134$), early-universe variation of fundamental constants, early dark energy, primordial magnetic fields, or modified recombination. Our data are consistent with standard BBN, the FIRAS-inferred CMB temperature, a dark matter component that is collisionless and with only a small fraction allowed as axion-like particles, a cosmological constant, and the late-time growth rate predicted by general relativity. We find no statistically significant preference for a departure from the baseline $Λ$CDM model. In general, models introduced to increase the Hubble constant or to decrease the amplitude of density fluctuations inferred from the primary CMB are not favored by our data. △ Less

Submitted 24 June, 2025; v1 submitted 18 March, 2025; originally announced March 2025.

Comments: Matches version accepted by JCAP. 56+36 pages, 46+13 figures, abstract abridged here. Part of ACT DR6 suite of papers. Data located at https://lambda.gsfc.nasa.gov/product/act/act_dr6.02/

The Atacama Cosmology Telescope: DR6 Power Spectra, Likelihoods and $Λ$CDM Parameters

Authors: Thibaut Louis, Adrien La Posta, Zachary Atkins, Hidde T. Jense, Irene Abril-Cabezas, Graeme E. Addison, Peter A. R. Ade, Simone Aiola, Tommy Alford, David Alonso, Mandana Amiri, Rui An, Jason E. Austermann, Eleonora Barbavara, Nicholas Battaglia, Elia Stefano Battistelli, James A. Beall, Rachel Bean, Ali Beheshti, Benjamin Beringue, Tanay Bhandarkar, Emily Biermann, Boris Bolliet, J Richard Bond, Erminia Calabrese , et al. (143 additional authors not shown)

Abstract: We present power spectra of the cosmic microwave background (CMB) anisotropy in temperature and polarization, measured from the Data Release 6 maps made from Atacama Cosmology Telescope (ACT) data. These cover 19,000 deg$^2$ of sky in bands centered at 98, 150 and 220 GHz, with white noise levels three times lower than Planck in polarization. We find that the ACT angular power spectra estimated ov… ▽ More We present power spectra of the cosmic microwave background (CMB) anisotropy in temperature and polarization, measured from the Data Release 6 maps made from Atacama Cosmology Telescope (ACT) data. These cover 19,000 deg$^2$ of sky in bands centered at 98, 150 and 220 GHz, with white noise levels three times lower than Planck in polarization. We find that the ACT angular power spectra estimated over 10,000 deg$^2$, and measured to arcminute scales in TT, TE and EE, are well fit by the sum of CMB and foregrounds, where the CMB spectra are described by the $Λ$CDM model. Combining ACT with larger-scale Planck data, the joint P-ACT dataset provides tight limits on the ingredients, expansion rate, and initial conditions of the universe. We find similar constraining power, and consistent results, from either the Planck power spectra or from ACT combined with WMAP data, as well as from either temperature or polarization in the joint P-ACT dataset. When combined with CMB lensing from ACT and Planck, and baryon acoustic oscillation data from DESI DR1, we measure a baryon density of $Ω_b h^2=0.0226\pm0.0001$, a cold dark matter density of $Ω_c h^2=0.118\pm0.001$, a Hubble constant of $H_0=68.22\pm0.36$ km/s/Mpc, a spectral index of $n_s=0.974\pm0.003$, and an amplitude of density fluctuations of $σ_8=0.813\pm0.005$. Including the DESI DR2 data tightens the Hubble constant to $H_0=68.43\pm0.27$ km/s/Mpc; $Λ$CDM parameters agree between the P-ACT and DESI DR2 data at the $1.6σ$ level. We find no evidence for excess lensing in the power spectrum, and no departure from spatial flatness. The contribution from Sunyaev-Zel'dovich (SZ) anisotropy is detected at high significance; we find evidence for a tilt with suppressed small-scale power compared to our baseline SZ template spectrum, consistent with hydrodynamical simulations with feedback. △ Less

Submitted 24 June, 2025; v1 submitted 18 March, 2025; originally announced March 2025.

Comments: Matching version accepted by JCAP. Data located at https://lambda.gsfc.nasa.gov/product/act/act_dr6.02, code located at https://github.com/simonsobs/PSpipe

The Atacama Cosmology Telescope: DR6 Maps

Authors: Sigurd Naess, Yilun Guan, Adriaan J. Duivenvoorden, Matthew Hasselfield, Yuhan Wang, Irene Abril-Cabezas, Graeme E. Addison, Peter A. R. Ade, Simone Aiola, Tommy Alford, David Alonso, Mandana Amiri, Rui An, Zachary Atkins, Jason E. Austermann, Eleonora Barbavara, Nicholas Battaglia, Elia Stefano Battistelli, James A. Beall, Rachel Bean, Ali Beheshti, Benjamin Beringue, Tanay Bhandarkar, Emily Biermann, Boris Bolliet , et al. (141 additional authors not shown)

Abstract: We present Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) maps of the Cosmic Microwave Background temperature and polarization anisotropy at arcminute resolution over three frequency bands centered on 98, 150 and 220 GHz. The maps are based on data collected with the AdvancedACT camera over the period 2017--2022 and cover 19,000 square degrees with a median combined depth of 10 uK arcmin.… ▽ More We present Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) maps of the Cosmic Microwave Background temperature and polarization anisotropy at arcminute resolution over three frequency bands centered on 98, 150 and 220 GHz. The maps are based on data collected with the AdvancedACT camera over the period 2017--2022 and cover 19,000 square degrees with a median combined depth of 10 uK arcmin. We describe the instrument, mapmaking and map properties and illustrate them with a number of figures and tables. The ACT DR6 maps and derived products are available on LAMBDA at https://lambda.gsfc.nasa.gov/product/act/actadv_prod_table.html. We also provide an interactive web atlas at https://phy-act1.princeton.edu/public/snaess/actpol/dr6/atlas and HiPS data sets in Aladin (e.g. https://alasky.cds.unistra.fr/ACT/DR4DR6/color_CMB). △ Less

Submitted 18 March, 2025; originally announced March 2025.

Comments: 37+25 pages, 21+19 figures, 12+1 tables. Part of DR6 suite of papers submitted to JCAP. Data located at https://lambda.gsfc.nasa.gov/product/act/actadv_prod_table.html

The Simons Observatory: Science Goals and Forecasts for the Enhanced Large Aperture Telescope

Authors: The Simons Observatory Collaboration, M. Abitbol, I. Abril-Cabezas, S. Adachi, P. Ade, A. E. Adler, P. Agrawal, J. Aguirre, Z. Ahmed, S. Aiola, T. Alford, A. Ali, D. Alonso, M. A. Alvarez, R. An, K. Arnold, P. Ashton, Z. Atkins, J. Austermann, S. Azzoni, C. Baccigalupi, A. Baleato Lizancos, D. Barron, P. Barry, J. Bartlett , et al. (397 additional authors not shown)

Abstract: We describe updated scientific goals for the wide-field, millimeter-wave survey that will be produced by the Simons Observatory (SO). Significant upgrades to the 6-meter SO Large Aperture Telescope (LAT) are expected to be complete by 2028, and will include a doubled mapping speed with 30,000 new detectors and an automated data reduction pipeline. In addition, a new photovoltaic array will supply… ▽ More We describe updated scientific goals for the wide-field, millimeter-wave survey that will be produced by the Simons Observatory (SO). Significant upgrades to the 6-meter SO Large Aperture Telescope (LAT) are expected to be complete by 2028, and will include a doubled mapping speed with 30,000 new detectors and an automated data reduction pipeline. In addition, a new photovoltaic array will supply most of the observatory's power. The LAT survey will cover about 60% of the sky at a regular observing cadence, with five times the angular resolution and ten times the map depth of Planck. The science goals are to: (1) determine the physical conditions in the early universe and constrain the existence of new light particles; (2) measure the integrated distribution of mass, electron pressure, and electron momentum in the late-time universe, and, in combination with optical surveys, determine the neutrino mass and the effects of dark energy via tomographic measurements of the growth of structure at $z < 3$; (3) measure the distribution of electron density and pressure around galaxy groups and clusters, and calibrate the effects of energy input from galaxy formation on the surrounding environment; (4) produce a sample of more than 30,000 galaxy clusters, and more than 100,000 extragalactic millimeter sources, including regularly sampled AGN light-curves, to study these sources and their emission physics; (5) measure the polarized emission from magnetically aligned dust grains in our Galaxy, to study the properties of dust and the role of magnetic fields in star formation; (6) constrain asteroid regoliths, search for Trans-Neptunian Objects, and either detect or eliminate large portions of the phase space in the search for Planet 9; and (7) provide a powerful new window into the transient universe on time scales of minutes to years, concurrent with observations from Rubin of overlapping sky. △ Less

Submitted 7 August, 2025; v1 submitted 1 March, 2025; originally announced March 2025.

Comments: 45 pages, 7 figures; abstract slightly abridged; matches JCAP accepted version. Author contributions to this paper are available at https://simonsobservatory.org/wp-content/uploads/2025/03/Author-contribution-statement-20250228.pdf

The X-ray Integral Field Unit at the end of the Athena reformulation phase

Authors: Philippe Peille, Didier Barret, Edoardo Cucchetti, Vincent Albouys, Luigi Piro, Aurora Simionescu, Massimo Cappi, Elise Bellouard, Céline Cénac-Morthé, Christophe Daniel, Alice Pradines, Alexis Finoguenov, Richard Kelley, J. Miguel Mas-Hesse, Stéphane Paltani, Gregor Rauw, Agata Rozanska, Jiri Svoboda, Joern Wilms, Marc Audard, Enrico Bozzo, Elisa Costantini, Mauro Dadina, Thomas Dauser, Anne Decourchelle , et al. (257 additional authors not shown)

Abstract: The Athena mission entered a redefinition phase in July 2022, driven by the imperative to reduce the mission cost at completion for the European Space Agency below an acceptable target, while maintaining the flagship nature of its science return. This notably called for a complete redesign of the X-ray Integral Field Unit (X-IFU) cryogenic architecture towards a simpler active cooling chain. Passi… ▽ More The Athena mission entered a redefinition phase in July 2022, driven by the imperative to reduce the mission cost at completion for the European Space Agency below an acceptable target, while maintaining the flagship nature of its science return. This notably called for a complete redesign of the X-ray Integral Field Unit (X-IFU) cryogenic architecture towards a simpler active cooling chain. Passive cooling via successive radiative panels at spacecraft level is now used to provide a 50 K thermal environment to an X-IFU owned cryostat. 4.5 K cooling is achieved via a single remote active cryocooler unit, while a multi-stage Adiabatic Demagnetization Refrigerator ensures heat lift down to the 50 mK required by the detectors. Amidst these changes, the core concept of the readout chain remains robust, employing Transition Edge Sensor microcalorimeters and a SQUID-based Time-Division Multiplexing scheme. Noteworthy is the introduction of a slower pixel. This enables an increase in the multiplexing factor (from 34 to 48) without compromising the instrument energy resolution, hence keeping significant system margins to the new 4 eV resolution requirement. This allows reducing the number of channels by more than a factor two, and thus the resource demands on the system, while keeping a 4' field of view (compared to 5' before). In this article, we will give an overview of this new architecture, before detailing its anticipated performances. Finally, we will present the new X-IFU schedule, with its short term focus on demonstration activities towards a mission adoption in early 2027. △ Less

Submitted 15 February, 2025; originally announced February 2025.

Comments: 44 pages, 14 figures, accepted for publication in Experimental Astronomy

Direct Imaging of Transition-Edge Sensors with Scanning SQUID Microscopy

Authors: Samantha Walker, Austin Kaczmarek, Jason Austermann, Douglas Bennett, Shannon M. Duff, Johannes Hubmayr, Ben Keller, Kelsey Morgan, Colin C. Murphy, Daniel Swetz, Joel Ullom, Michael D. Niemack, Katja C. Nowack

Abstract: Significant advancements have been made in understanding the physics of transition-edge sensors (TESs) over the past decade. However, key questions remain, particularly a detailed understanding of the current-dependent resistance of these detectors when biased within their superconducting transition. We use scanning superconducting quantum interference device (SQUID) microscopy (SSM) to image the… ▽ More Significant advancements have been made in understanding the physics of transition-edge sensors (TESs) over the past decade. However, key questions remain, particularly a detailed understanding of the current-dependent resistance of these detectors when biased within their superconducting transition. We use scanning superconducting quantum interference device (SQUID) microscopy (SSM) to image the local diamagnetic response of aluminum-manganese alloy (Al-Mn) transition-edge sensors (TESs) near their critical temperature of approximately 175 mK. By doing so, we gain insights into how the device dimensions influence TES transition width, which in turn affects device operation and informs optimal device design. Our images reveal that the Al-Mn thin film near the niobium (Nb) leads exhibits an excess diamagnetic response at temperatures several milli-Kelvin (mK) higher than the bulk of the film farther from the contacts. A possible origin of this behavior is a longitudinal proximity effect between the Nb and Al-Mn where the TES acts as a weak link between superconducting leads. We discuss how this effect shapes the temperature dependence of the resistance as the spacing between the leads decreases. This work demonstrates that magnetic imaging with SSM is a powerful tool for local characterization of superconducting detectors. △ Less

Submitted 2 October, 2024; originally announced October 2024.

Comments: 5 pages, 4 figures, Applied Superconductivity Conference (ASC 2024) proceedings, submitted to IEEE Transactions on Applied Superconductivity (IEEE TAS)

System performance of a cryogenic test-bed for the time-division multiplexing readout for NewAthena X-IFU

Authors: Davide Vaccaro, Jan van der Kuur, Paul van der Hulst, Tobias Vos, Martin de Wit, Luciano Gottardi, Kevin Ravensberg, Emanuele Taralli, Joseph Adams, Simon Bandler, Douglas Bennet, James Chervenak, Bertrand Doriese, Malcolm Durkin, Johnathon Gard, Carl Reintsema, Kazuhiro Sakai, Steven Smith, Joel Ullom, Nicholas Wakeham, Jan-Willem den Herder, Brian jackson, Pourya Khosropanah, Jian-Rong Gao, Peter Roelfsema , et al. (1 additional authors not shown)

Abstract: The X-ray Integral Field Unit (X-IFU) is an instrument of ESA's future NewAthena space observatory, with the goal to provide high-energy resolution ($<$ 4 eV at X-ray energies up to 7 keV) and high-spatial resolution (9") spectroscopic imaging over the X-ray energy range from 200 eV to 12 keV, by means of an array of about 1500 transition-edge sensors (TES) read out via SQUID time-division multipl… ▽ More The X-ray Integral Field Unit (X-IFU) is an instrument of ESA's future NewAthena space observatory, with the goal to provide high-energy resolution ($<$ 4 eV at X-ray energies up to 7 keV) and high-spatial resolution (9") spectroscopic imaging over the X-ray energy range from 200 eV to 12 keV, by means of an array of about 1500 transition-edge sensors (TES) read out via SQUID time-division multiplexing (TDM). A TDM-based laboratory test-bed has been assembled at SRON, hosting an array of $75\times 75\ \upmu$m$^2$ TESs that are read out via 2-column $\times$ 32-row TDM. A system component that is critical to high-performance operation is the wiring harness that connects the room-temperature electronics to the cryogenic readout componentry. We report here on our characterization of such a test-bed, whose harness has a length close to what envisioned for X-IFU, which allowed to achieve a co-added energy resolution at a level of 2.7~eV FWHM at 6~keV via 32-row readout. In addition, we provide an outlook on the integration of TDM readout into the X-IFU Focal-Plane Assembly Development Model. △ Less

Submitted 5 November, 2024; v1 submitted 9 September, 2024; originally announced September 2024.

Comments: Submitted for publication to Journal of Astronomical Telescopes, Instrumentation and Systems. arXiv admin note: text overlap with arXiv:2403.02978

Journal ref: Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 10, Issue 4, 046002 (December 2024)

In-Flight Performance of Spider's 280 GHz Receivers

Authors: Elle C. Shaw, P. A. R. Ade, S. Akers, M. Amiri, J. Austermann, J. Beall, D. T. Becker, S. J. Benton, A. S. Bergman, J. J. Bock, J. R. Bond, S. A. Bryan, H. C. Chiang, C. R. Contaldi, R. S. Domagalski, O. Doré, S. M. Duff, A. J. Duivenvoorden, H. K. Eriksen, M. Farhang, J. P. Filippini, L. M. Fissel, A. A. Fraisse, K. Freese, M. Galloway , et al. (62 additional authors not shown)

Abstract: SPIDER is a balloon-borne instrument designed to map the cosmic microwave background at degree-angular scales in the presence of Galactic foregrounds. SPIDER has mapped a large sky area in the Southern Hemisphere using more than 2000 transition-edge sensors (TESs) during two NASA Long Duration Balloon flights above the Antarctic continent. During its first flight in January 2015, SPIDER observed i… ▽ More SPIDER is a balloon-borne instrument designed to map the cosmic microwave background at degree-angular scales in the presence of Galactic foregrounds. SPIDER has mapped a large sky area in the Southern Hemisphere using more than 2000 transition-edge sensors (TESs) during two NASA Long Duration Balloon flights above the Antarctic continent. During its first flight in January 2015, SPIDER observed in the 95 GHz and 150 GHz frequency bands, setting constraints on the B-mode signature of primordial gravitational waves. Its second flight in the 2022-2023 season added new receivers at 280 GHz, each using an array of TESs coupled to the sky through feedhorns formed from stacks of silicon wafers. These receivers are optimized to produce deep maps of polarized Galactic dust emission over a large sky area, providing a unique data set with lasting value to the field. We describe the instrument's performance during SPIDER's second flight, focusing on the performance of the 280 GHz receivers. We include details on the flight, in-band optical loading at float, and an early analysis of detector noise. △ Less

Submitted 17 August, 2025; v1 submitted 19 August, 2024; originally announced August 2024.

Comments: 20 pages, 11 figures, Author's version of the manuscript accepted for publication in Journal of Astronomical Telescopes, Instruments, and Systems (JATIS) in December 2024

Journal ref: J. Astron. Telesc. Instrum. Syst. 10(4), 044012 (2024)

Simons Observatory: Pre-deployment Performance of a Large Aperture Telescope Optics Tube in the 90 and 150 GHz Spectral Bands

Authors: Carlos E. Sierra, Kathleen Harrington, Shreya Sutariya, Thomas Alford, Anna M. Kofman, Grace E. Chesmore, Jason E. Austermann, Andrew Bazarko, James A. Beall, Tanay Bhandarkar, Mark J. Devlin, Simon R. Dicker, Peter N. Dow, Shannon M. Duff, Daniel Dutcher, Nicholas Galitzki, Joseph E. Golec, John C. Groh, Jon E. Gudmundsson, Saianeesh K. Haridas, Erin Healy, Johannes Hubmayr, Jeffrey Iuliano, Bradley R. Johnson, Claire S. Lessler , et al. (20 additional authors not shown)

Abstract: The Simons Observatory will map the temperature and polarization over half of the sky, at millimeter wavelengths in six spectral bands from the Atacama Desert in Chile. These data will provide new insights into the genesis, content, and history of our Universe; the astrophysics of galaxies and galaxy clusters; objects in our solar system; and time-varying astrophysical phenomena. This ambitious ne… ▽ More The Simons Observatory will map the temperature and polarization over half of the sky, at millimeter wavelengths in six spectral bands from the Atacama Desert in Chile. These data will provide new insights into the genesis, content, and history of our Universe; the astrophysics of galaxies and galaxy clusters; objects in our solar system; and time-varying astrophysical phenomena. This ambitious new instrument suite, initially comprising three 0.5 m small-aperture telescopes and one 6 m large aperture telescope, is designed using a common combination of new technologies and new implementations to realize an observatory significantly more capable than the previous generation. In this paper, we present the pre-deployment performance of the first mid-frequency "optics tube" which will be fielded on the large aperture telescope with sensitivity to the 90 and 150 GHz spectral bands. This optics tube contains lenses, filters, detectors, and readout components, all of which operate at cryogenic temperatures. It is one of seven that form the core of the large aperture telescope receiver in its initial deployment. We describe this optics tube, including details of comprehensive testing methods, new techniques for beam and passband characterization, and its measured performance. The performance metrics include beams, optical efficiency, passbands, and forecasts for the on-sky performance of the system. We forecast a sensitivity that exceeds the requirements of the large aperture telescope with greater than 30% margin in each spectral band, and predict that the instrument will realize diffraction-limited performance and the expected detector passbands. △ Less

Submitted 10 May, 2024; originally announced May 2024.

The Simons Observatory: Design, integration, and testing of the small aperture telescopes

Authors: Nicholas Galitzki, Tran Tsan, Jake Spisak, Michael Randall, Max Silva-Feaver, Joseph Seibert, Jacob Lashner, Shunsuke Adachi, Sean M. Adkins, Thomas Alford, Kam Arnold, Peter C. Ashton, Jason E. Austermann, Carlo Baccigalupi, Andrew Bazarko, James A. Beall, Sanah Bhimani, Bryce Bixler, Gabriele Coppi, Lance Corbett, Kevin D. Crowley, Kevin T. Crowley, Samuel Day-Weiss, Simon Dicker, Peter N. Dow , et al. (55 additional authors not shown)

Abstract: The Simons Observatory (SO) is a cosmic microwave background (CMB) survey experiment that includes small-aperture telescopes (SATs) observing from an altitude of 5,200 m in the Atacama Desert in Chile. The SO SATs will cover six spectral bands between 27 and 280 GHz to search for primordial B-modes to a sensitivity of $σ(r)=0.002$, with quantified systematic errors well below this value. Each SAT… ▽ More The Simons Observatory (SO) is a cosmic microwave background (CMB) survey experiment that includes small-aperture telescopes (SATs) observing from an altitude of 5,200 m in the Atacama Desert in Chile. The SO SATs will cover six spectral bands between 27 and 280 GHz to search for primordial B-modes to a sensitivity of $σ(r)=0.002$, with quantified systematic errors well below this value. Each SAT is a self-contained cryogenic telescope with a 35$^\circ$ field of view, 42 cm diameter optical aperture, 40 K half-wave plate, 1 K refractive optics, and $<0.1$ K focal plane that holds $>12,000$ TES detectors. We describe the nominal design of the SATs and present details about the integration and testing for one operating at 93 and 145 GHz. △ Less

Submitted 10 May, 2024; v1 submitted 9 May, 2024; originally announced May 2024.

The Simons Observatory: Production-level Fabrication of the Mid- and Ultra-High-Frequency Wafers

Authors: Shannon M. Duff, Jason Austermann, James A. Beall, David P. Daniel, Johannes Hubmayr, Greg C. Jaehnig, Bradley R. Johnson, Dante Jones, Michael J. Link, Tammy J. Lucas, Rita F. Sonka, Suzanne T. Staggs, Joel Ullom, Yuhan Wang

Abstract: The Simons Observatory (SO) is a cosmic microwave background instrumentation suite in the Atacama Desert of Chile. More than 65,000 polarization-sensitive transition-edge sensor (TES) bolometers will be fielded in the frequency range spanning 27 to 280 GHz, with three separate dichroic designs. The mid-frequency 90/150 GHz and ultra-high-frequency 220/280 GHz detector arrays, fabricated at NIST, a… ▽ More The Simons Observatory (SO) is a cosmic microwave background instrumentation suite in the Atacama Desert of Chile. More than 65,000 polarization-sensitive transition-edge sensor (TES) bolometers will be fielded in the frequency range spanning 27 to 280 GHz, with three separate dichroic designs. The mid-frequency 90/150 GHz and ultra-high-frequency 220/280 GHz detector arrays, fabricated at NIST, account for 39 of 49 total detector modules and implement the feedhorn-fed orthomode transducer (OMT)-coupled TES bolometer architecture. A robust production-level fabrication framework for these detector arrays and the monolithic DC/RF routing wafers has been developed, which includes single device prototyping, process monitoring techniques, in-process metrology, and cryogenic measurements of critical film properties. Application of this framework has resulted in timely delivery of nearly 100 total superconducting focal plane components to SO with 88% of detector wafers meeting nominal criteria for integration into a detector module: a channel yield > 95% and Tc in the targeted range. △ Less

Submitted 26 March, 2024; originally announced March 2024.

Comments: 10 pages, 6 figures. Proceedings of the 20th International Conference on Low Temperature Detectors (LTD20). Submitted to JLTP

The BLAST Observatory: A Sensitivity Study for Far-IR Balloon-borne Polarimeters

Authors: The BLAST Observatory Collaboration, Gabriele Coppi, Simon Dicker, James E. Aguirre, Jason E. Austermann, James A. Beall, Susan E. Clark, Erin G. Cox, Mark J. Devlin, Laura M. Fissel, Nicholas Galitzki, Brandon S. Hensley, Johannes Hubmayr, Sergio Molinari, Federico Nati, Giles Novak, Eugenio Schisano, Juan D. Soler, Carole E. Tucker, Joel N. Ullom, Anna Vaskuri, Michael R. Vissers, Jordan D. Wheeler, Mario Zannoni

Abstract: Sensitive wide-field observations of polarized thermal emission from interstellar dust grains will allow astronomers to address key outstanding questions about the life cycle of matter and energy driving the formation of stars and the evolution of galaxies. Stratospheric balloon-borne telescopes can map this polarized emission at far-infrared wavelengths near the peak of the dust thermal spectrum… ▽ More Sensitive wide-field observations of polarized thermal emission from interstellar dust grains will allow astronomers to address key outstanding questions about the life cycle of matter and energy driving the formation of stars and the evolution of galaxies. Stratospheric balloon-borne telescopes can map this polarized emission at far-infrared wavelengths near the peak of the dust thermal spectrum - wavelengths that are inaccessible from the ground. In this paper we address the sensitivity achievable by a Super Pressure Balloon (SPB) polarimetry mission, using as an example the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) Observatory. By launching from Wanaka, New Zealand, BLAST Observatory can obtain a 30-day flight with excellent sky coverage - overcoming limitations of past experiments that suffered from short flight duration and/or launch sites with poor coverage of nearby star-forming regions. This proposed polarimetry mission will map large regions of the sky at sub-arcminute resolution, with simultaneous observations at 175, 250, and 350 $μm$, using a total of 8274 microwave kinetic inductance detectors. Here, we describe the scientific motivation for the BLAST Observatory, the proposed implementation, and the forecasting methods used to predict its sensitivity. We also compare our forecasted experiment sensitivity with other facilities. △ Less

Submitted 23 May, 2024; v1 submitted 25 January, 2024; originally announced January 2024.

Comments: Published in PASP

Journal ref: 2024 PASP 136 035003

Crosstalk effects in microwave SQUID multiplexed TES bolometer readout

Authors: John C. Groh, Zeeshan Ahmed, Shawn W. Henderson, Johannes Hubmayr, John A. B. Mates, Maximiliano Silva-Feaver, Joel Ullom, Cyndia Yu

Abstract: Transition-edge sensor (TES) bolometers are broadly used for background-limited astrophysical measurements from the far-infrared to mm-waves. Many planned future instruments require increasingly large detector arrays, but their scalability is limited by their cryogenic readout electronics. Microwave SQUID multiplexing offers a highly capable scaling solution through the use of inherently broadband… ▽ More Transition-edge sensor (TES) bolometers are broadly used for background-limited astrophysical measurements from the far-infrared to mm-waves. Many planned future instruments require increasingly large detector arrays, but their scalability is limited by their cryogenic readout electronics. Microwave SQUID multiplexing offers a highly capable scaling solution through the use of inherently broadband circuitry, enabling readout of hundreds to thousands of channels per microwave line. As with any multiplexing technique, the channelization mechanism gives rise to electrical crosstalk which must be understood and controlled so as to not degrade the instrument sensitivity. Here, we explore implications relevant for TES bolometer array applications, focusing in particular on upcoming mm-wave observatories such as the Simons Observatory and AliCPT. We model the relative contributions of the various underlying crosstalk mechanisms, evaluate the difference between fixed-tone and tone-tracking readout systems, and discuss ways in which crosstalk nonlinearity will complicate on-sky measurements. △ Less

Submitted 8 April, 2024; v1 submitted 9 November, 2023; originally announced November 2023.

Comments: Accepted for publication in the Journal of Low Temperature Physics

End-to-End Modeling of the TDM Readout System for CMB-S4

Authors: David C. Goldfinger, Zeeshan Ahmed, Darcy R. Barron, W. Bertrand Doriese, Malcolm Durkin, Jeffrey P. Filippini, Gunther Haller, Shawn W. Henderson, Ryan Herbst, Johannes Hubmayr, Kent Irwin, Ben Reese, Leonid Sapozhnikov, Keith L. Thompson, Joel Ullom, Michael R. Vissers

Abstract: The CMB-S4 experiment is developing next-generation ground-based microwave telescopes to observe the Cosmic Microwave Background with unprecedented sensitivity. This will require an order of magnitude increase in the 100 mK detector count, which in turn increases the demands on the readout system. The CMB-S4 readout will use time division multiplexing (TDM), taking advantage of faster switches and… ▽ More The CMB-S4 experiment is developing next-generation ground-based microwave telescopes to observe the Cosmic Microwave Background with unprecedented sensitivity. This will require an order of magnitude increase in the 100 mK detector count, which in turn increases the demands on the readout system. The CMB-S4 readout will use time division multiplexing (TDM), taking advantage of faster switches and amplifiers in order to achieve an increased multiplexing factor. To facilitate the design of the new readout system, we have developed a model that predicts the bandwidth and noise performance of this circuity and its interconnections. This is then used to set requirements on individual components in order to meet the performance necessary for the full system. We present an overview of this model and compare the model results to the performance of both legacy and prototype readout hardware. △ Less

Submitted 17 November, 2023; v1 submitted 7 November, 2023; originally announced November 2023.

Comments: This manuscript was submitted to the Journal of Low Temperature Physics as part of the special issue "LTD20", supporting the conference contribution RP-005

The Atacama Cosmology Telescope: High-resolution component-separated maps across one-third of the sky

Authors: William R. Coulton, Mathew S. Madhavacheril, Adriaan J. Duivenvoorden, J. Colin Hill, Irene Abril-Cabezas, Peter A. R. Ade, Simone Aiola, Tommy Alford, Mandana Amiri, Stefania Amodeo, Rui An, Zachary Atkins, Jason E. Austermann, Nicholas Battaglia, Elia Stefano Battistelli, James A. Beall, Rachel Bean, Benjamin Beringue, Tanay Bhandarkar, Emily Biermann, Boris Bolliet, J Richard Bond, Hongbo Cai, Erminia Calabrese, Victoria Calafut , et al. (129 additional authors not shown)

Abstract: Observations of the millimeter sky contain valuable information on a number of signals, including the blackbody cosmic microwave background (CMB), Galactic emissions, and the Compton-$y$ distortion due to the thermal Sunyaev-Zel'dovich (tSZ) effect. Extracting new insight into cosmological and astrophysical questions often requires combining multi-wavelength observations to spectrally isolate one… ▽ More Observations of the millimeter sky contain valuable information on a number of signals, including the blackbody cosmic microwave background (CMB), Galactic emissions, and the Compton-$y$ distortion due to the thermal Sunyaev-Zel'dovich (tSZ) effect. Extracting new insight into cosmological and astrophysical questions often requires combining multi-wavelength observations to spectrally isolate one component. In this work, we present a new arcminute-resolution Compton-$y$ map, which traces out the line-of-sight-integrated electron pressure, as well as maps of the CMB in intensity and E-mode polarization, across a third of the sky (around 13,000 sq.~deg.). We produce these through a joint analysis of data from the Atacama Cosmology Telescope (ACT) Data Release 4 and 6 at frequencies of roughly 93, 148, and 225 GHz, together with data from the \textit{Planck} satellite at frequencies between 30 GHz and 545 GHz. We present detailed verification of an internal linear combination pipeline implemented in a needlet frame that allows us to efficiently suppress Galactic contamination and account for spatial variations in the ACT instrument noise. These maps provide a significant advance, in noise levels and resolution, over the existing \textit{Planck} component-separated maps and will enable a host of science goals including studies of cluster and galaxy astrophysics, inferences of the cosmic velocity field, primordial non-Gaussianity searches, and gravitational lensing reconstruction of the CMB. △ Less

Submitted 3 July, 2023; originally announced July 2023.

Comments: The Compton-y map and associated products will be made publicly available upon publication of the paper. The CMB T and E mode maps will be made available when the DR6 maps are made public

The Atacama Cosmology Telescope: DR6 Gravitational Lensing Map and Cosmological Parameters

Authors: Mathew S. Madhavacheril, Frank J. Qu, Blake D. Sherwin, Niall MacCrann, Yaqiong Li, Irene Abril-Cabezas, Peter A. R. Ade, Simone Aiola, Tommy Alford, Mandana Amiri, Stefania Amodeo, Rui An, Zachary Atkins, Jason E. Austermann, Nicholas Battaglia, Elia Stefano Battistelli, James A. Beall, Rachel Bean, Benjamin Beringue, Tanay Bhandarkar, Emily Biermann, Boris Bolliet, J Richard Bond, Hongbo Cai, Erminia Calabrese , et al. (134 additional authors not shown)

Abstract: We present cosmological constraints from a gravitational lensing mass map covering 9400 sq. deg. reconstructed from CMB measurements made by the Atacama Cosmology Telescope (ACT) from 2017 to 2021. In combination with BAO measurements (from SDSS and 6dF), we obtain the amplitude of matter fluctuations $σ_8 = 0.819 \pm 0.015$ at 1.8% precision, $S_8\equivσ_8({Ω_{\rm m}}/0.3)^{0.5}=0.840\pm0.028$ an… ▽ More We present cosmological constraints from a gravitational lensing mass map covering 9400 sq. deg. reconstructed from CMB measurements made by the Atacama Cosmology Telescope (ACT) from 2017 to 2021. In combination with BAO measurements (from SDSS and 6dF), we obtain the amplitude of matter fluctuations $σ_8 = 0.819 \pm 0.015$ at 1.8% precision, $S_8\equivσ_8({Ω_{\rm m}}/0.3)^{0.5}=0.840\pm0.028$ and the Hubble constant $H_0= (68.3 \pm 1.1)\, \text{km}\,\text{s}^{-1}\,\text{Mpc}^{-1}$ at 1.6% precision. A joint constraint with CMB lensing measured by the Planck satellite yields even more precise values: $σ_8 = 0.812 \pm 0.013$, $S_8\equivσ_8({Ω_{\rm m}}/0.3)^{0.5}=0.831\pm0.023$ and $H_0= (68.1 \pm 1.0)\, \text{km}\,\text{s}^{-1}\,\text{Mpc}^{-1}$. These measurements agree well with $Λ$CDM-model extrapolations from the CMB anisotropies measured by Planck. To compare these constraints to those from the KiDS, DES, and HSC galaxy surveys, we revisit those data sets with a uniform set of assumptions, and find $S_8$ from all three surveys are lower than that from ACT+Planck lensing by varying levels ranging from 1.7-2.1$σ$. These results motivate further measurements and comparison, not just between the CMB anisotropies and galaxy lensing, but also between CMB lensing probing $z\sim 0.5-5$ on mostly-linear scales and galaxy lensing at $z\sim 0.5$ on smaller scales. We combine our CMB lensing measurements with CMB anisotropies to constrain extensions of $Λ$CDM, limiting the sum of the neutrino masses to $\sum m_ν < 0.13$ eV (95% c.l.), for example. Our results provide independent confirmation that the universe is spatially flat, conforms with general relativity, and is described remarkably well by the $Λ$CDM model, while paving a promising path for neutrino physics with gravitational lensing from upcoming ground-based CMB surveys. △ Less

Submitted 12 August, 2024; v1 submitted 11 April, 2023; originally announced April 2023.

Comments: 32 pages, 17 figures, replaced with version accepted in ApJ (Feb 2024). Cosmological likelihood data and mass maps are public here: https://lambda.gsfc.nasa.gov/product/act/actadv_prod_table.html ; likelihood software is here: https://github.com/ACTCollaboration/act_dr6_lenslike . Also see companion papers Qu et al and MacCrann et al

Journal ref: The Astrophysical Journal, Volume 962, 2024, Page 113

The Atacama Cosmology Telescope: Mitigating the impact of extragalactic foregrounds for the DR6 CMB lensing analysis

Authors: Niall MacCrann, Blake D. Sherwin, Frank J. Qu, Toshiya Namikawa, Mathew S. Madhavacheril, Irene Abril-Cabezas, Rui An, Jason E. Austermann, Nicholas Battaglia, Elia S. Battistelli, James A. Beall, Boris Bolliet, J. Richard Bond, Hongbo Cai, Erminia Calabrese, William R. Coulton, Omar Darwish, Shannon M. Duff, Adriaan J. Duivenvoorden, Jo Dunkley, Gerrit S. Farren, Simone Ferraro, Joseph E. Golec, Yilun Guan, Dongwon Han , et al. (25 additional authors not shown)

Abstract: We investigate the impact and mitigation of extragalactic foregrounds for the CMB lensing power spectrum analysis of Atacama Cosmology Telescope (ACT) data release 6 (DR6) data. Two independent microwave sky simulations are used to test a range of mitigation strategies. We demonstrate that finding and then subtracting point sources, finding and then subtracting models of clusters, and using a prof… ▽ More We investigate the impact and mitigation of extragalactic foregrounds for the CMB lensing power spectrum analysis of Atacama Cosmology Telescope (ACT) data release 6 (DR6) data. Two independent microwave sky simulations are used to test a range of mitigation strategies. We demonstrate that finding and then subtracting point sources, finding and then subtracting models of clusters, and using a profile bias-hardened lensing estimator, together reduce the fractional biases to well below statistical uncertainties, with the inferred lensing amplitude, $A_{\mathrm{lens}}$, biased by less than $0.2σ$. We also show that another method where a model for the cosmic infrared background (CIB) contribution is deprojected and high frequency data from Planck is included has similar performance. Other frequency-cleaned options do not perform as well, incurring either a large noise cost, or resulting in biased recovery of the lensing spectrum. In addition to these simulation-based tests, we also present null tests performed on the ACT DR6 data which test for sensitivity of our lensing spectrum estimation to differences in foreground levels between the two ACT frequencies used, while nulling the CMB lensing signal. These tests pass whether the nulling is performed at the map or bandpower level. The CIB-deprojected measurement performed on the DR6 data is consistent with our baseline measurement, implying contamination from the CIB is unlikely to significantly bias the DR6 lensing spectrum. This collection of tests gives confidence that the ACT DR6 lensing measurements and cosmological constraints presented in companion papers to this work are robust to extragalactic foregrounds. △ Less

Submitted 11 April, 2023; originally announced April 2023.

Comments: Companion paper to Qu et al and Madhavacheril et al

Improved microwave SQUID multiplexer readout using a kinetic-inductance traveling-wave parametric amplifier

Authors: M. Malnou, J. A. B. Mates, M. R. Vissers, L. R. Vale, D. R. Schmidt, D. A. Bennett, J. Gao, J. N. Ullom

Abstract: We report on the use of a kinetic-inductance traveling-wave parametric amplifier (KITWPA) as the first amplifier in the readout chain of a microwave superconducting quantum interference device (SQUID) multiplexer (umux). This umux is designed to multiplex signals from arrays of low temperature detectors such as superconducting transition-edge sensor microcalorimeters. When modulated with a periodi… ▽ More We report on the use of a kinetic-inductance traveling-wave parametric amplifier (KITWPA) as the first amplifier in the readout chain of a microwave superconducting quantum interference device (SQUID) multiplexer (umux). This umux is designed to multiplex signals from arrays of low temperature detectors such as superconducting transition-edge sensor microcalorimeters. When modulated with a periodic flux-ramp to linearize the SQUID response, the flux noise improves, on average, from $1.6$ $μΦ_0/\sqrt{\mathrm{Hz}}$ with the KITWPA off, to $0.77$ $μΦ_0/\sqrt{\mathrm{Hz}}$ with the KITWPA on. When statically biasing the umux to the maximally flux-sensitive point, the flux noise drops from $0.45$ $μΦ_0/\sqrt{\mathrm{Hz}}$ to $0.2$ $μΦ_0/\sqrt{\mathrm{Hz}}$. We validate this new readout scheme by coupling a transition-edge sensor microcalorimeter to the umux and detecting background radiation. The combination of umux and KITWPA provides a variety of new capabilities including improved detector sensitivity and more efficient bandwidth utilization. △ Less

Submitted 7 March, 2023; originally announced March 2023.

ASCENT - A balloon-borne hard X-ray imaging spectroscopy telescope using transition edge sensor microcalorimeter detectors

Authors: Fabian Kislat, Daniel Becker, Douglas Bennett, Adrika Dasgupta, Joseph Fowler, Christopher L. Fryer, Johnathon Gard, Ephraim Gau, Danielle Gurgew, Keon Harmon, Takayuki Hayashi, Scott Heatwole, Md Arman Hossen, Henric Krawczynski, R. James Lanzi, Jason Legere, John A. B. Mates, Mark McConnell, Johanna Nagy, Takashi Okajima, Toshiki Sato, Daniel Schmidt, Sean Spooner, Daniel Swetz, Keisuke Tamura , et al. (4 additional authors not shown)

Abstract: Core collapse supernovae are thought to be one of the main sources in the galaxy of elements heavier than iron. Understanding the origin of the elements is thus tightly linked to our understanding of the explosion mechanism of supernovae and supernova nucleosynthesis. X-ray and gamma-ray observations of young supernova remnants, combined with improved theoretical modeling, have resulted in enormou… ▽ More Core collapse supernovae are thought to be one of the main sources in the galaxy of elements heavier than iron. Understanding the origin of the elements is thus tightly linked to our understanding of the explosion mechanism of supernovae and supernova nucleosynthesis. X-ray and gamma-ray observations of young supernova remnants, combined with improved theoretical modeling, have resulted in enormous improvements in our knowledge of these events. The isotope ${}^{44}$Ti is one of the most sensitive probes of the innermost regions of the core collapse engine, and its spatial and velocity distribution are key observables. Hard X-ray imaging spectroscopy with the Nuclear Spectroscopic Telescope Array (NuSTAR) has provided new insights into the structure of the supernova remnant Cassiopeia A (Cas A), establishing the convective nature of the supernova engine. However, many questions about the details of this engine remain. We present here the concept for a balloon-borne follow-up mission called ASCENT (A SuperConducting ENergetic x-ray Telescope). ASCENT uses transition edge sensor gamma-ray microcalorimeter detectors with a demonstrated 55 eV Full Width Half Maximum (FWHM) energy resolution at 97 keV. This 8--16-fold improvement in energy resolution over NuSTAR will allow high resolution imaging and spectroscopy of the ${}^{44}$Ti emission. This will allow a detailed reconstruction of gamma-ray line redshifts, widths, and shapes, allowing us to address questions such as: What is the source of the neutron star "kicks"? What is the dominant production pathway for ${}^{44}$Ti? Is the engine of Cas A unique? △ Less

Submitted 4 January, 2023; originally announced January 2023.

Comments: 23 pages, 11 figures

A 50 mK test bench for demonstration of the readout chain of Athena/X-IFU

Authors: Florent Castellani, Sophie Beaumont, François Pajot, Gilles Roudil, Joseph Adams, Simon Bandler, James Chervenak, Christophe Daniel, Edward V Denison, W Bertrand Doriese, Michel Dupieux, Malcolm Durkin, Hervé Geoffray, Gene C Hilton, David Murat, Yann Parot, Philippe Peille, Damien Prêle, Laurent Ravera, Carl D Reintsema, Kazuhiro Sakai, Robert W Stevens, Joel N Ullom, Leila R Vale, Nicholas Wakeham

Abstract: The X-IFU (X-ray Integral Field Unit) onboard the large ESA mission Athena (Advanced Telescope for High ENergy Astrophysics), planned to be launched in the mid 2030s, will be a cryogenic X-ray imaging spectrometer operating at 55 mK. It will provide unprecedented spatially resolved high-resolution spectroscopy (2.5 eV FWHM up to 7 keV) in the 0.2-12 keV energy range thanks to its array of TES (Tra… ▽ More The X-IFU (X-ray Integral Field Unit) onboard the large ESA mission Athena (Advanced Telescope for High ENergy Astrophysics), planned to be launched in the mid 2030s, will be a cryogenic X-ray imaging spectrometer operating at 55 mK. It will provide unprecedented spatially resolved high-resolution spectroscopy (2.5 eV FWHM up to 7 keV) in the 0.2-12 keV energy range thanks to its array of TES (Transition Edge Sensors) microcalorimeters of more than 2k pixel. The detection chain of the instrument is developed by an international collaboration: the detector array by NASA/GSFC, the cold electronics by NIST, the cold amplifier by VTT, the WFEE (Warm Front-End Electronics) by APC, the DRE (Digital Readout Electronics) by IRAP and a focal plane assembly by SRON. To assess the operation of the complete readout chain of the X-IFU, a 50 mK test bench based on a kilo-pixel array of microcalorimeters from NASA/GSFC has been developed at IRAP in collaboration with CNES. Validation of the test bench has been performed with an intermediate detection chain entirely from NIST and Goddard. Next planned activities include the integration of DRE and WFEE prototypes in order to perform an end-to-end demonstration of a complete X-IFU detection chain. △ Less

Submitted 9 September, 2022; originally announced September 2022.

Comments: Proceedings-of-the-SPIE-The-International-Society-for-Optical-Engineering SPIE-Int. Soc. Opt. Eng, In press

The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

Authors: Didier Barret, Vincent Albouys, Jan-Willem den Herder, Luigi Piro, Massimo Cappi, Juhani Huovelin, Richard Kelley, J. Miguel Mas-Hesse, Stéphane Paltani, Gregor Rauw, Agata Rozanska, Jiri Svoboda, Joern Wilms, Noriko Yamasaki, Marc Audard, Simon Bandler, Marco Barbera, Xavier Barcons, Enrico Bozzo, Maria Teresa Ceballos, Ivan Charles, Elisa Costantini, Thomas Dauser, Anne Decourchelle, Lionel Duband , et al. (274 additional authors not shown)

Abstract: The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer, studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory, a versatile observatory designed to address the Hot and Energetic Universe science theme, selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), it aims to provide sp… ▽ More The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer, studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory, a versatile observatory designed to address the Hot and Energetic Universe science theme, selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), it aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over an hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR, browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters. Finally we briefly discuss on the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, and touch on communication and outreach activities, the consortium organisation, and finally on the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. (abridged). △ Less

Submitted 28 November, 2022; v1 submitted 30 August, 2022; originally announced August 2022.

Comments: 48 pages, 29 figures, Accepted for publication in Experimental Astronomy with minor editing

CCAT-prime: The 850 GHz camera for Prime-Cam on FYST

Authors: Scott C. Chapman, Anthony I. Huber, Adrian K. Sinclair, Jordan D. Wheeler, Jason E. Austermann, James Beall, James Burgoyne, Steve K. Choi, Abigail Crites, Cody J. Duell, Jesslyn Devina, Jiansong Gao, Mike Fich, Doug Henke, Terry Herter, Doug Johnstone, Lewis B. G. Knee, Michael D. Niemack, Kayla M. Rossi, Gordon Stacey, Joel Tsuchitori, Joel Ullom, Jeff Van Lanen, Eve M. Vavagiakis, Michael Vissers , et al. (1 additional authors not shown)

Abstract: The Fred Young Submillimeter Telescope (FYST) at the Cerro-Chajnantor Atacama Telescope prime (CCAT- prime) Facility will host Prime-Cam as a powerful, first generation camera with imaging polarimeters working at several wavelengths and spectroscopic instruments aimed at intensity mapping during the Epoch of Reionization. Here we introduce the 850 GHz (350 micron) instrument module. This will be t… ▽ More The Fred Young Submillimeter Telescope (FYST) at the Cerro-Chajnantor Atacama Telescope prime (CCAT- prime) Facility will host Prime-Cam as a powerful, first generation camera with imaging polarimeters working at several wavelengths and spectroscopic instruments aimed at intensity mapping during the Epoch of Reionization. Here we introduce the 850 GHz (350 micron) instrument module. This will be the highest frequency module in Prime-Cam and the most novel for astronomical and cosmological surveys, taking full advantage of the atmospheric transparency at the high 5600 meter CCAT-prime siting on Cerro Chajnantor. With a 1.1 deg diameter field, the 850 GHz module will deploy ~40,000 Kinetic Inductance Detectors (KIDs) with Silicon platelet feedhorn coupling (both fabricated at NIST), and will provide unprecedented broadband intensity and polarization measurement capabilities. The 850 GHz module will be key to addressing pressing astrophysical questions regarding galaxy formation, Big Bang cosmology, and star formation within our own Galaxy. We present the motivation and overall design for the module, and initial laboratory characterization. △ Less

Submitted 22 August, 2022; originally announced August 2022.

Comments: 15 pages, accepted for publication in SPIE

SLAC Microresonator RF (SMuRF) Electronics: A tone-tracking readout system for superconducting microwave resonator arrays

Authors: Cyndia Yu, Zeeshan Ahmed, Josef C. Frisch, Shawn W. Henderson, Max Silva-Feaver, Kam Arnold, David Brown, Jake Connors, Ari J. Cukierman, J. Mitch D'Ewart, Bradley J. Dober, John E. Dusatko, Gunther Haller, Ryan Herbst, Gene C. Hilton, Johannes Hubmayr, Kent D. Irwin, Chao-Lin Kuo, John A. B. Mates, Larry Ruckman, Joel Ullom, Leila Vale, Daniel D. Van Winkle, Jesus Vasquez, Edward Young

Abstract: We describe the newest generation of the SLAC Microresonator RF (SMuRF) electronics, a warm digital control and readout system for microwave-frequency resonator-based cryogenic detector and multiplexer systems such as microwave SQUID multiplexers ($μ$mux) or microwave kinetic inductance detectors (MKIDs). Ultra-sensitive measurements in particle physics and astronomy increasingly rely on large arr… ▽ More We describe the newest generation of the SLAC Microresonator RF (SMuRF) electronics, a warm digital control and readout system for microwave-frequency resonator-based cryogenic detector and multiplexer systems such as microwave SQUID multiplexers ($μ$mux) or microwave kinetic inductance detectors (MKIDs). Ultra-sensitive measurements in particle physics and astronomy increasingly rely on large arrays of cryogenic sensors, which in turn necessitate highly multiplexed readout and accompanying room-temperature electronics. Microwave-frequency resonators are a popular tool for cryogenic multiplexing, with the potential to multiplex thousands of detector channels on one readout line. The SMuRF system provides the capability for reading out up to 3328 channels across a 4-8 GHz bandwidth. Notably, the SMuRF system is unique in its implementation of a closed-loop tone-tracking algorithm that minimizes RF power transmitted to the cold amplifier, substantially relaxing system linearity requirements and effective noise from intermodulation products. Here we present a description of the hardware, firmware, and software systems of the SMuRF electronics, comparing achieved performance with science-driven design requirements. We focus in particular on the case of large channel count, low bandwidth applications, but the system has been easily reconfigured for high bandwidth applications. The system described here has been successfully deployed in lab settings and field sites around the world and is baselined for use on upcoming large-scale observatories. △ Less

Submitted 22 August, 2022; originally announced August 2022.

Comments: 28 pages, 25 figures, + references. Comments welcome!

CCAT-prime: Design of the Mod-Cam receiver and 280 GHz MKID instrument module

Authors: Eve M. Vavagiakis, Cody J. Duell, Jason Austermann, James Beall, Tanay Bhandarkar, Scott C. Chapman, Steve K. Choi, Gabriele Coppi, Simon Dicker, Mark Devlin, Rodrigo G. Freundt, Jiansong Gao, Christopher Groppi, Terry L. Herter, Zachary B. Huber, Johannes Hubmayr, Doug Johnstone, Ben Keller, Anna M. Kofman, Yaqiong Li, Philip Mauskopf, Jeff McMahon, Jenna Moore, Colin C. Murphy, Michael D. Niemack , et al. (11 additional authors not shown)

Abstract: Mod-Cam is a first light and commissioning instrument for the CCAT-prime project's six-meter aperture Fred Young Submillimeter Telescope (FYST), currently under construction at 5600 m on Cerro Chajnantor in Chile's Atacama Desert. Prime-Cam, a first-generation science instrument for FYST, will deliver over ten times greater mapping speed than current and near-term facilities for unprecedented 280-… ▽ More Mod-Cam is a first light and commissioning instrument for the CCAT-prime project's six-meter aperture Fred Young Submillimeter Telescope (FYST), currently under construction at 5600 m on Cerro Chajnantor in Chile's Atacama Desert. Prime-Cam, a first-generation science instrument for FYST, will deliver over ten times greater mapping speed than current and near-term facilities for unprecedented 280-850 GHz broadband and spectroscopic measurements with microwave kinetic inductance detectors (MKIDs). CCAT-prime will address a suite of science goals, from Big Bang cosmology to star formation and galaxy evolution over cosmic time. Mod-Cam deployment on FYST with a 280 GHz instrument module containing MKID arrays is planned for early science observations in 2024. Mod-Cam will be used to test instrument modules for Prime-Cam, which can house up to seven instrument modules. We discuss the design and status of the 0.9 m diameter, 1.8 m long Mod-Cam receiver and 40 cm diameter 280 GHz instrument module, with cold stages at 40 K, 4 K, 1 K, and 100 mK. We also describe the instrument module's cryogenic readout designs to enable the readout of more than 10,000 MKIDs across 18 networks. △ Less

Submitted 10 August, 2022; originally announced August 2022.

Comments: Presented at SPIE Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI

The 511-CAM Mission: A Pointed 511 keV Gamma-Ray Telescope with a Focal Plane Detector Made of Stacked Transition Edge Sensor Microcalorimeter Arrays

Authors: Farzane Shirazi, Md. Arman Hossen, Daniel Becker, Daniel Schmidt, Daniel Swetz, Douglas Bennett, Dana Braun, Ephraim Gau, Fabian Kislat, Johnathon Gard, John Mates, Joel Weber, Nicole Rodriguez Cavero, Sohee Chun, Lindsey Lisalda, Andrew West, Bhupal Dev, Francesc Ferrer, Richard Bose, Joel Ullom, Henric Krawczynski

Abstract: The 511 keV gamma-ray emission from the galactic center region may fully or partially originate from the annihilation of positrons from dark matter particles with electrons from the interstellar medium. Alternatively, the positrons could be created by astrophysical sources, involving exclusively standard model physics. We describe here a new concept for a 511 keV mission called 511-CAM (511 keV ga… ▽ More The 511 keV gamma-ray emission from the galactic center region may fully or partially originate from the annihilation of positrons from dark matter particles with electrons from the interstellar medium. Alternatively, the positrons could be created by astrophysical sources, involving exclusively standard model physics. We describe here a new concept for a 511 keV mission called 511-CAM (511 keV gamma-ray CAmera using Micro-calorimeters) that combines focusing gamma-ray optics with a stack of Transition Edge Sensor (TES) microcalorimeter arrays in the focal plane. The 511-CAM detector assembly has a projected 511 keV energy resolution of 390 eV Full Width Half Maximum (FWHM) or better, and improves by a factor of at least 11 on the performance of state-of-the-art Ge-based Compton telescopes. Combining this unprecedented energy resolution with sub-arcmin angular resolutions afforded by Laue lens or channeling optics could make substantial contributions to identifying the origin of the 511 keV emission by discovering and characterizing point sources and measuring line-of-sight velocities of the emitting plasmas. △ Less

Submitted 12 September, 2023; v1 submitted 29 June, 2022; originally announced June 2022.

Comments: 21 pages, 11 figures, 2 tables; revised manuscript that addressed the referee's comments

Journal ref: Journal of Astronomical Telescopes, Instruments, and Systems, Volume 9, id. 024006 (2023)

Bandwidth and Aliasing in the Microwave SQUID Multiplexer

Authors: Cyndia Yu, Zeeshan Ahmed, Jake A. Connors, J. Mitch D'Ewart, Bradley Dober, Josef C. Frisch, Shawn W. Henderson, Gene C. Hilton, Johannes Hubmayr, Stephen E. Kuenstner, J. A. Ben Mates, Maximiliano Silva-Feaver, Joel N. Ullom, Leila R. Vale, Dan Van Winkle, Edward Young

Abstract: The microwave SQUID multiplexer (umux) has enabled higher bandwidth or higher channel counts across a wide range of experiments in particle physics, astronomy, and spectroscopy. The large multiplexing factor coupled with recent commercial availability of microwave components and warm electronics readout systems make it an attractive candidate for systems requiring large cryogenic detector counts.… ▽ More The microwave SQUID multiplexer (umux) has enabled higher bandwidth or higher channel counts across a wide range of experiments in particle physics, astronomy, and spectroscopy. The large multiplexing factor coupled with recent commercial availability of microwave components and warm electronics readout systems make it an attractive candidate for systems requiring large cryogenic detector counts. Since the multiplexer is considered for both bolometric and calorimetric applications across several orders of magnitude of signal frequencies, understanding the bandwidth of the device and its interaction with readout electronics is key to appropriately designing and engineering systems. Here we discuss several important factors contributing to the bandwidth properties of umux systems, including the intrinsic device bandwidth, interactions with warm electronics readout systems, and aliasing. We present simulations and measurements of umux devices coupled with SLAC Microresonator RF (SMuRF) tone-tracking electronics and discuss several implications for future experimental design. △ Less

Submitted 17 June, 2022; originally announced June 2022.

Comments: Proceedings for Low Temperature Physics 2021, accepted for publication in Journal of Low Temperature Physics. 8 pages (including references), 5 figures

Performance of a Kinetic-Inductance Traveling-Wave Parametric Amplifier at 4 Kelvin: Toward an Alternative to Semiconductor Amplifiers

Authors: M. Malnou, J. Aumentado, M. R. Vissers, J. D. Wheeler, J. Hubmayr, J. N. Ullom, J. Gao

Abstract: Most microwave readout architectures in quantum computing or sensing rely on a semiconductor amplifier at 4 K, typically a high-electron mobility transistor (HEMT). Despite its remarkable noise performance, a conventional HEMT dissipates several milliwatts of power, posing a practical challenge to scale up the number of qubits or sensors addressed in these architectures. As an alternative, we pres… ▽ More Most microwave readout architectures in quantum computing or sensing rely on a semiconductor amplifier at 4 K, typically a high-electron mobility transistor (HEMT). Despite its remarkable noise performance, a conventional HEMT dissipates several milliwatts of power, posing a practical challenge to scale up the number of qubits or sensors addressed in these architectures. As an alternative, we present an amplification chain consisting of a kinetic-inductance traveling-wave parametric amplifier (KI-TWPA) placed at 4 K, followed by a HEMT placed at 70 K, and demonstrate a chain-added noise $T_Σ= 6.3\pm0.5$ K between 3.5 and 5.5 GHz. While, in principle, any parametric amplifier can be quantum limited even at 4 K, in practice we find the KI-TWPA's performance limited by the temperature of its inputs, and by an excess of noise $T_\mathrm{ex} = 1.9$ K. The dissipation of the KI-TWPA's rf pump constitutes the main power load at 4 K and is about one percent that of a HEMT. These combined noise and power dissipation values pave the way for the KI-TWPA's use as a replacement for semiconductor amplifiers. △ Less

Submitted 15 October, 2021; originally announced October 2021.

CCAT-prime Collaboration: Science Goals and Forecasts with Prime-Cam on the Fred Young Submillimeter Telescope

Authors: CCAT-Prime collaboration, M. Aravena, J. E. Austermann, K. Basu, N. Battaglia, B. Beringue, F. Bertoldi, F. Bigiel, J. R. Bond, P. C. Breysse, C. Broughton, R. Bustos, S. C. Chapman, M. Charmetant, S. K. Choi, D. T. Chung, S. E. Clark, N. F. Cothard, A. T. Crites, A. Dev, K. Douglas, C. J. Duell, R. Dunner, H. Ebina, J. Erler , et al. (62 additional authors not shown)

Abstract: We present a detailed overview of the science goals and predictions for the Prime-Cam direct detection camera/spectrometer being constructed by the CCAT-prime collaboration for dedicated use on the Fred Young Submillimeter Telescope (FYST). The FYST is a wide-field, 6-m aperture submillimeter telescope being built (first light in mid-2024) by an international consortium of institutions led by Corn… ▽ More We present a detailed overview of the science goals and predictions for the Prime-Cam direct detection camera/spectrometer being constructed by the CCAT-prime collaboration for dedicated use on the Fred Young Submillimeter Telescope (FYST). The FYST is a wide-field, 6-m aperture submillimeter telescope being built (first light in mid-2024) by an international consortium of institutions led by Cornell University and sited at more than 5600 meters on Cerro Chajnantor in northern Chile. Prime-Cam is one of two instruments planned for FYST and will provide unprecedented spectroscopic and broadband measurement capabilities to address important astrophysical questions ranging from Big Bang cosmology through reionization and the formation of the first galaxies to star formation within our own Milky Way galaxy. Prime-Cam on the FYST will have a mapping speed that is over ten times greater than existing and near-term facilities for high-redshift science and broadband polarimetric imaging at frequencies above 300 GHz. We describe details of the science program enabled by this system and our preliminary survey strategies. △ Less

Submitted 8 August, 2022; v1 submitted 21 July, 2021; originally announced July 2021.

Comments: 61 pages, 16 figures. Resubmitted to ApJSS July 11, 2022

Observations of compact sources in galaxy clusters using MUSTANG2

Authors: Simon R. Dicker, Elia S. Battistelli, Tanay Bhandarkar, Mark J. Devlin, Shannon M. Duff, Gene Hilton, Matt Hilton, Adam D. Hincks, Johannes Hubmayr, Kevin Huffenberger, John P. Hughes, Luca Di Mascolo, Brian S. Mason, J. A. B. Mates, Jeff McMahon, Tony Mroczkowski, Sigurd Naess, John Orlowski-Scherer, Bruce Partridge, Federico Radiconi, Charles Romero, Craig L. Sarazin, Neelima Sehgal, Jonathan Sievers, Cristóbal Sifón , et al. (4 additional authors not shown)

Abstract: Compact sources can cause scatter in the scaling relationships between the amplitude of the thermal Sunyaev-Zel'dovich Effect (tSZE) in galaxy clusters and cluster mass. Estimates of the importance of this scatter vary - largely due to limited data on sources in clusters at the frequencies at which tSZE cluster surveys operate. In this paper we present 90 GHz compact source measurements from a sam… ▽ More Compact sources can cause scatter in the scaling relationships between the amplitude of the thermal Sunyaev-Zel'dovich Effect (tSZE) in galaxy clusters and cluster mass. Estimates of the importance of this scatter vary - largely due to limited data on sources in clusters at the frequencies at which tSZE cluster surveys operate. In this paper we present 90 GHz compact source measurements from a sample of 30 clusters observed using the MUSTANG2 instrument on the Green Bank Telescope. We present simulations of how a source's flux density, spectral index, and angular separation from the cluster's center affect the measured tSZE in clusters detected by the Atacama Cosmology Telescope (ACT). By comparing the MUSTANG2 measurements with these simulations we calibrate an empirical relationship between 1.4 GHz flux densities from radio surveys and source contamination in ACT tSZE measurements. We find 3 per cent of the ACT clusters have more than a 20 per cent decrease in Compton-y but another 3 per cent have a 10 per cent increase in the Compton-y due to the matched filters used to find clusters. As sources affect the measured tSZE signal and hence the likelihood that a cluster will be detected, testing the level of source contamination in the tSZE signal using a tSZE selected catalog is inherently biased. We confirm this by comparing the ACT tSZE catalog with optically and X-ray selected cluster catalogs. There is a strong case for a large, high resolution survey of clusters to better characterize their source population. △ Less

Submitted 22 September, 2021; v1 submitted 14 July, 2021; originally announced July 2021.

Comments: 13 Pages, 10 figures, 2 tables, with 4 pages of online only figures at end. Published on-line in MNRAS on 22/9/2021

A high-resolution view of the filament of gas between Abell 399 and Abell 401 from the Atacama Cosmology Telescope and MUSTANG-2

Authors: Adam D. Hincks, Federico Radiconi, Charles Romero, Mathew S. Madhavacheril, Tony Mroczkowski, Jason E. Austermann, Eleonora Barbavara, Nicholas Battaglia, Elia Battistelli, J. Richard Bond, Erminia Calabrese, Paolo de Bernardis, Mark J. Devlin, Simon R. Dicker, Shannon M. Duff, Adriaan J. Duivenvoorden, Jo Dunkley, Rolando Dünner, Patricio A. Gallardo, Federica Govoni, J. Colin Hill, Matt Hilton, Johannes Hubmayr, John P. Hughes, Luca Lamagna , et al. (21 additional authors not shown)

Abstract: We report a significant detection of the hot intergalactic medium in the filamentary bridge connecting the galaxy clusters Abell 399 and Abell 401. This result is enabled by a low-noise, high-resolution map of the thermal Sunyaev-Zeldovich signal from the Atacama Cosmology Telescope (ACT) and Planck satellite. The ACT data provide the $1.65'$ resolution that allows us to clearly separate the profi… ▽ More We report a significant detection of the hot intergalactic medium in the filamentary bridge connecting the galaxy clusters Abell 399 and Abell 401. This result is enabled by a low-noise, high-resolution map of the thermal Sunyaev-Zeldovich signal from the Atacama Cosmology Telescope (ACT) and Planck satellite. The ACT data provide the $1.65'$ resolution that allows us to clearly separate the profiles of the clusters, whose centres are separated by $37'$, from the gas associated with the filament. A model that fits for only the two clusters is ruled out compared to one that includes a bridge component at $>5σ$. Using a gas temperature determined from Suzaku X-ray data, we infer a total mass of $(3.3\pm0.7)\times10^{14}\,\mathrm{M}_{\odot}$ associated with the filament, comprising about $8\%$ of the entire Abell 399-Abell 401 system. We fit two phenomenological models to the filamentary structure; the favoured model has a width transverse to the axis joining the clusters of ${\sim}1.9\,\mathrm{Mpc}$. When combined with the Suzaku data, we find a gas density of $(0.88\pm0.24)\times10^{-4}\,\mathrm{cm}^{-3}$, considerably lower than previously reported. We show that this can be fully explained by a geometry in which the axis joining Abell 399 and Abell 401 has a large component along the line of sight, such that the distance between the clusters is significantly greater than the $3.2\,\mathrm{Mpc}$ projected separation on the plane of the sky. Finally, we present initial results from higher resolution ($12.7"$ effective) imaging of the bridge with the MUSTANG-2 receiver on the Green Bank Telescope. △ Less

Submitted 26 November, 2021; v1 submitted 9 July, 2021; originally announced July 2021.

Comments: 23 pages, 10 figures, 3 tables. This is a pre-copyedited, author-produced PDF of an article accepted for publication in the Monthly Notices of the Royal Astronomical Society following peer review. The version of record is available online at: https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stab3391/6442294

The Simons Observatory microwave SQUID multiplexing detector module design

Authors: Heather McCarrick, Erin Healy, Zeeshan Ahmed, Kam Arnold, Zachary Atkins, Jason E. Austermann, Tanay Bhandarkar, Jim A. Beall, Sarah Marie Bruno, Steve K. Choi, Jake Connors, Nicholas F. Cothard, Kevin D. Crowley, Simon Dicker, Bradley Dober, Cody J. Duell, Shannon M. Duff, Daniel Dutcher, Josef C. Frisch, Nicholas Galitzki, Megan B. Gralla, Jon E. Gudmundsson, Shawn W. Henderson, Gene C. Hilton, Shuay-Pwu Patty Ho , et al. (34 additional authors not shown)

Abstract: Advances in cosmic microwave background (CMB) science depend on increasing the number of sensitive detectors observing the sky. New instruments deploy large arrays of superconducting transition-edge sensor (TES) bolometers tiled densely into ever larger focal planes. High multiplexing factors reduce the thermal loading on the cryogenic receivers and simplify their design. We present the design of… ▽ More Advances in cosmic microwave background (CMB) science depend on increasing the number of sensitive detectors observing the sky. New instruments deploy large arrays of superconducting transition-edge sensor (TES) bolometers tiled densely into ever larger focal planes. High multiplexing factors reduce the thermal loading on the cryogenic receivers and simplify their design. We present the design of focal-plane modules with an order of magnitude higher multiplexing factor than has previously been achieved with TES bolometers. We focus on the novel cold readout component, which employs microwave SQUID multiplexing ($μ$mux). Simons Observatory will use 49 modules containing 60,000 bolometers to make exquisitely sensitive measurements of the CMB. We validate the focal-plane module design, presenting measurements of the readout component with and without a prototype detector array of 1728 polarization-sensitive bolometers coupled to feedhorns. The readout component achieves a $95\%$ yield and a 910 multiplexing factor. The median white noise of each readout channel is 65 $\mathrm{pA/\sqrt{Hz}}$. This impacts the projected SO mapping speed by $< 8\%$, which is less than is assumed in the sensitivity projections. The results validate the full functionality of the module. We discuss the measured performance in the context of SO science requirements, which are exceeded. △ Less

Submitted 16 September, 2021; v1 submitted 28 June, 2021; originally announced June 2021.

Comments: Accepted to The Astrophysical Journal

Journal ref: 2021 ApJ 922 38

The Simons Observatory: the Large Aperture Telescope (LAT)

Authors: Zhilei Xu, Shunsuke Adachi, Peter Ade, J. A. Beall, Tanay Bhandarkar, J. Richard Bond, Grace E. Chesmore, Yuji Chinone, Steve K. Choi, Jake A. Connors, Gabriele Coppi, Nicholas F. Cothard, Kevin D. Crowley, Mark Devlin, Simon Dicker, Bradley Dober, Shannon M. Duff, Nicholas Galitzki, Patricio A. Gallardo, Joseph E. Golec, Jon E. Gudmundsson, Saianeesh K. Haridas, Kathleen Harrington, Carlos Hervias-Caimapo, Shuay-Pwu Patty Ho , et al. (35 additional authors not shown)

Abstract: The Simons Observatory (SO) is a Cosmic Microwave Background (CMB) experiment to observe the microwave sky in six frequency bands from 30GHz to 290GHz. The Observatory -- at $\sim$5200m altitude -- comprises three Small Aperture Telescopes (SATs) and one Large Aperture Telescope (LAT) at the Atacama Desert, Chile. This research note describes the design and current status of the LAT along with its… ▽ More The Simons Observatory (SO) is a Cosmic Microwave Background (CMB) experiment to observe the microwave sky in six frequency bands from 30GHz to 290GHz. The Observatory -- at $\sim$5200m altitude -- comprises three Small Aperture Telescopes (SATs) and one Large Aperture Telescope (LAT) at the Atacama Desert, Chile. This research note describes the design and current status of the LAT along with its future timeline. △ Less

Submitted 29 April, 2021; v1 submitted 19 April, 2021; originally announced April 2021.

Comments: 4 pages, 1 figure

Journal ref: Research Notes AAS, 5, 100 (2021)

The Atacama Cosmology Telescope: Summary of DR4 and DR5 Data Products and Data Access

Authors: Maya Mallaby-Kay, Zachary Atkins, Simone Aiola, Stefania Amodeo, Jason E. Austermann, James A. Beall, Daniel T. Becker, J. Richard Bond, Erminia Calabrese, Grace E. Chesmore, Steve K. Choi, Kevin T. Crowley, Omar Darwish, Edwawd V. Denison, Mark J. Devlin, Shannon M. Duff, Adriaan J. Duivenvoorden, Jo Dunkley, Simone Ferraro, Kyra Fichman, Patricio A. Gallardo, Joseph E. Golec, Yilun Guan, Dongwon Han, Matthew Hasselfield , et al. (35 additional authors not shown)

Abstract: Two recent large data releases for the Atacama Cosmology Telescope (ACT), called DR4 and DR5, are available for public access. These data include temperature and polarization maps that cover nearly half the sky at arcminute resolution in three frequency bands; lensing maps and component-separated maps covering ~ 2,100 deg^2 of sky; derived power spectra and cosmological likelihoods; a catalog of o… ▽ More Two recent large data releases for the Atacama Cosmology Telescope (ACT), called DR4 and DR5, are available for public access. These data include temperature and polarization maps that cover nearly half the sky at arcminute resolution in three frequency bands; lensing maps and component-separated maps covering ~ 2,100 deg^2 of sky; derived power spectra and cosmological likelihoods; a catalog of over 4,000 galaxy clusters; and supporting ancillary products including beam functions and masks. The data and products are described in a suite of ACT papers; here we provide a summary. In order to facilitate ease of access to these data we present a set of Jupyter IPython notebooks developed to introduce users to DR4, DR5, and the tools needed to analyze these data. The data products (excluding simulations) and the set of notebooks are publicly available on the NASA Legacy Archive for Microwave Background Data Analysis (LAMBDA); simulation products are available on the National Energy Research Scientific Computing Center (NERSC). △ Less

Submitted 29 April, 2021; v1 submitted 4 March, 2021; originally announced March 2021.

Comments: Accepted to ApJS. 21 pages, 8 figures. Data and notebooks available on LAMBDA https://lambda.gsfc.nasa.gov/product/act/

The Simons Observatory Large Aperture Telescope Receiver

Authors: Ningfeng Zhu, Tanay Bhandarkar, Gabriele Coppi, Anna M. Kofman, John L. Orlowski-Scherer, Zhilei Xu, Shunsuke Adachi, Peter Ade, Simone Aiola, Jason Austermann, Andrew O. Bazarko, James A. Beall, Sanah Bhimani, J. Richard Bond, Grace E. Chesmore, Steve K. Choi, Jake Connors, Nicholas F. Cothard, Mark Devlin, Simon Dicker, Bradley Dober, Cody J. Duell, Shannon M. Duff, Rolando Dünner, Giulio Fabbian , et al. (46 additional authors not shown)

Abstract: The Simons Observatory (SO) Large Aperture Telescope Receiver (LATR) will be coupled to the Large Aperture Telescope located at an elevation of 5,200 m on Cerro Toco in Chile. The resulting instrument will produce arcminute-resolution millimeter-wave maps of half the sky with unprecedented precision. The LATR is the largest cryogenic millimeter-wave camera built to date with a diameter of 2.4 m an… ▽ More The Simons Observatory (SO) Large Aperture Telescope Receiver (LATR) will be coupled to the Large Aperture Telescope located at an elevation of 5,200 m on Cerro Toco in Chile. The resulting instrument will produce arcminute-resolution millimeter-wave maps of half the sky with unprecedented precision. The LATR is the largest cryogenic millimeter-wave camera built to date with a diameter of 2.4 m and a length of 2.6 m. It cools 1200 kg of material to 4 K and 200 kg to 100 mk, the operating temperature of the bolometric detectors with bands centered around 27, 39, 93, 145, 225, and 280 GHz. Ultimately, the LATR will accommodate 13 40 cm diameter optics tubes, each with three detector wafers and a total of 62,000 detectors. The LATR design must simultaneously maintain the optical alignment of the system, control stray light, provide cryogenic isolation, limit thermal gradients, and minimize the time to cool the system from room temperature to 100 mK. The interplay between these competing factors poses unique challenges. We discuss the trade studies involved with the design, the final optimization, the construction, and ultimate performance of the system. △ Less

Submitted 3 March, 2021; originally announced March 2021.

Overview of the Medium and High Frequency Telescopes of the LiteBIRD satellite mission

Authors: L. Montier, B. Mot, P. de Bernardis, B. Maffei, G. Pisano, F. Columbro, J. E. Gudmundsson, S. Henrot-Versillé, L. Lamagna, J. Montgomery, T. Prouvé, M. Russell, G. Savini, S. Stever, K. L. Thompson, M. Tsujimoto, C. Tucker, B. Westbrook, P. A. R. Ade, A. Adler, E. Allys, K. Arnold, D. Auguste, J. Aumont, R. Aurlien , et al. (212 additional authors not shown)

Abstract: LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular… ▽ More LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular scales, and over 15 frequency bands from 34GHz to 448GHz. The LiteBIRD instruments consist of three telescopes, namely the Low-, Medium- and High-Frequency Telescope (respectively LFT, MFT and HFT). We present in this paper an overview of the design of the Medium-Frequency Telescope (89-224GHz) and the High-Frequency Telescope (166-448GHz), the so-called MHFT, under European responsibility, which are two cryogenic refractive telescopes cooled down to 5K. They include a continuous rotating half-wave plate as the first optical element, two high-density polyethylene (HDPE) lenses and more than three thousand transition-edge sensor (TES) detectors cooled to 100mK. We provide an overview of the concept design and the remaining specific challenges that we have to face in order to achieve the scientific goals of LiteBIRD. △ Less

Submitted 1 February, 2021; originally announced February 2021.

Comments: SPIE Conference

Journal ref: Proc. of SPIE Vol. 11443 14432G (2020)

LiteBIRD: JAXA's new strategic L-class mission for all-sky surveys of cosmic microwave background polarization

Authors: M. Hazumi, P. A. R. Ade, A. Adler, E. Allys, K. Arnold, D. Auguste, J. Aumont, R. Aurlien, J. Austermann, C. Baccigalupi, A. J. Banday, R. Banjeri, R. B. Barreiro, S. Basak, J. Beall, D. Beck, S. Beckman, J. Bermejo, P. de Bernardis, M. Bersanelli, J. Bonis, J. Borrill, F. Boulanger, S. Bounissou, M. Brilenkov , et al. (213 additional authors not shown)

Abstract: LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. JAXA selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with its expected launch in the late 2020s using JAXA's H3 rocket. LiteBIRD plans to map the cosmic microwave backgrou… ▽ More LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. JAXA selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with its expected launch in the late 2020s using JAXA's H3 rocket. LiteBIRD plans to map the cosmic microwave background (CMB) polarization over the full sky with unprecedented precision. Its main scientific objective is to carry out a definitive search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with an insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. To this end, LiteBIRD will perform full-sky surveys for three years at the Sun-Earth Lagrangian point L2 for 15 frequency bands between 34 and 448 GHz with three telescopes, to achieve a total sensitivity of 2.16 micro K-arcmin with a typical angular resolution of 0.5 deg. at 100GHz. We provide an overview of the LiteBIRD project, including scientific objectives, mission requirements, top-level system requirements, operation concept, and expected scientific outcomes. △ Less

Submitted 29 January, 2021; originally announced January 2021.

Comments: 20 pages, 9 figures

Journal ref: Proc. of SPIE Vol. 11443 114432F (2020)

The design of the Ali CMB Polarization Telescope receiver

Authors: Maria Salatino, Jason E. Austermann, Keith L. Thompson, Peter A. R. Ade, Xiran Bai, James A. Beall, Dan T. Becker, Yifu Cai, Zhi Chang, Ding Chen, Pisin Chen, Jake Connors, Jacques Delabrouille, Bradley Dober, Shannon M. Duff, Guanhua Gao, Shamik Ghosh, Richard C. Givhan, Gene C. Hilton, Bin Hu, Johannes Hubmayr, Ethan D. Karpel, Chao-Lin Kuo, Hong Li, Mingzhe Li , et al. (50 additional authors not shown)

Abstract: Ali CMB Polarization Telescope (AliCPT-1) is the first CMB degree-scale polarimeter to be deployed on the Tibetan plateau at 5,250m above sea level. AliCPT-1 is a 90/150 GHz 72 cm aperture, two-lens refracting telescope cooled down to 4 K. Alumina lenses, 800mm in diameter, image the CMB in a 33.4° field of view on a 636mm wide focal plane. The modularized focal plane consists of dichroic polariza… ▽ More Ali CMB Polarization Telescope (AliCPT-1) is the first CMB degree-scale polarimeter to be deployed on the Tibetan plateau at 5,250m above sea level. AliCPT-1 is a 90/150 GHz 72 cm aperture, two-lens refracting telescope cooled down to 4 K. Alumina lenses, 800mm in diameter, image the CMB in a 33.4° field of view on a 636mm wide focal plane. The modularized focal plane consists of dichroic polarization-sensitive Transition-Edge Sensors (TESes). Each module includes 1,704 optically active TESes fabricated on a 150mm diameter silicon wafer. Each TES array is read out with a microwave multiplexing readout system capable of a multiplexing factor up to 2,048. Such a large multiplexing factor has allowed the practical deployment of tens of thousands of detectors, enabling the design of a receiver that can operate up to 19 TES arrays for a total of 32,376 TESes. AliCPT-1 leverages the technological advancements in the detector design from multiple generations of previously successful feedhorn-coupled polarimeters, and in the instrument design from BICEP-3, but applied on a larger scale. The cryostat receiver is currently under integration and testing. During the first deployment year, the focal plane will be populated with up to 4 TES arrays. Further TES arrays will be deployed in the following years, fully populating the focal plane with 19 arrays on the fourth deployment year. Here we present the AliCPT-1 receiver design, and how the design has been optimized to meet the experimental requirements. △ Less

Submitted 23 January, 2021; originally announced January 2021.

Comments: Proc. SPIE, 11453, 114532A (2020)

Journal ref: Proceedings of SPIE, 'Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X', Volume 11453, 114532A (2020)

The Atacama Cosmology Telescope: Detection of the Pairwise Kinematic Sunyaev-Zel'dovich Effect with SDSS DR15 Galaxies

Authors: Victoria Calafut, Patricio A. Gallardo, Eve M. Vavagiakis, Stefania Amodeo, Simone Aiola, Jason E. Austermann, Nicholas Battaglia, Elia S. Battistelli, James A. Beall, Rachel Bean, J. Richard Bond, Erminia Calabrese, Steve K. Choi, Nicholas F. Cothard, Mark J. Devlin, Cody J. Duell, S. M. Duff, Adriaan J. Duivenvoorden, Jo Dunkley, Rolando Dunner, Simone Ferraro, Yilun Guan, J. Colin Hill, Matt Hilton, Renee Hlozek , et al. (27 additional authors not shown)

Abstract: We present a 5.4$σ$ detection of the pairwise kinematic Sunyaev-Zel'dovich (kSZ) effect using Atacama Cosmology Telescope (ACT) and $\it{Planck}$ CMB observations in combination with Luminous Red Galaxy samples from the Sloan Digital Sky Survey (SDSS) DR15 catalog. Results are obtained using three ACT CMB maps: co-added 150 GHz and 98 GHz maps, combining observations from 2008-2018 (ACT DR5), whic… ▽ More We present a 5.4$σ$ detection of the pairwise kinematic Sunyaev-Zel'dovich (kSZ) effect using Atacama Cosmology Telescope (ACT) and $\it{Planck}$ CMB observations in combination with Luminous Red Galaxy samples from the Sloan Digital Sky Survey (SDSS) DR15 catalog. Results are obtained using three ACT CMB maps: co-added 150 GHz and 98 GHz maps, combining observations from 2008-2018 (ACT DR5), which overlap with SDSS DR15 over 3,700 sq. deg., and a component-separated map using night-time only observations from 2014-2015 (ACT DR4), overlapping with SDSS DR15 over 2,089 sq. deg. Comparisons of the results from these three maps provide consistency checks in relation to potential frequency-dependent foreground contamination. A total of 343,647 galaxies are used as tracers to identify and locate galaxy groups and clusters from which the kSZ signal is extracted using aperture photometry. We consider the impact of various aperture photometry assumptions and covariance estimation methods on the signal extraction. Theoretical predictions of the pairwise velocities are used to obtain best-fit, mass-averaged, optical depth estimates for each of five luminosity-selected tracer samples. A comparison of the kSZ-derived optical depth measurements obtained here to those derived from the thermal SZ effect for the same sample is presented in a companion paper. △ Less

Submitted 24 August, 2021; v1 submitted 20 January, 2021; originally announced January 2021.

Comments: 17 pages, 10 figures. Updated to match published version in PRD

Journal ref: Phys. Rev. D 104, 043502 (2021)

The Atacama Cosmology Telescope: Probing the Baryon Content of SDSS DR15 Galaxies with the Thermal and Kinematic Sunyaev-Zel'dovich Effects

Authors: Eve M. Vavagiakis, Patricio A. Gallardo, Victoria Calafut, Stefania Amodeo, Simone Aiola, Jason E. Austermann, Nicholas Battaglia, Elia S. Battistelli, James A. Beall, Rachel Bean, J. Richard Bond, Erminia Calabrese, Steve K. Choi, Nicholas F. Cothard, Mark J. Devlin, Cody J. Duell, S. M. Duff, Adriaan J. Duivenvoorden, Jo Dunkley, Rolando Dunner, Simone Ferraro, Yilun Guan, J. Colin Hill, Matt Hilton, Renee Hlozek , et al. (27 additional authors not shown)

Abstract: We present high signal-to-noise measurements (up to 12$σ$) of the average thermal Sunyaev Zel'dovich (tSZ) effect from optically selected galaxy groups and clusters and estimate their baryon content within a 2.1$^\prime$ radius aperture. Sources from the Sloan Digital Sky Survey (SDSS) Baryon Oscillation Spectroscopic Survey (BOSS) DR15 catalog overlap with 3,700 sq. deg. of sky observed by the At… ▽ More We present high signal-to-noise measurements (up to 12$σ$) of the average thermal Sunyaev Zel'dovich (tSZ) effect from optically selected galaxy groups and clusters and estimate their baryon content within a 2.1$^\prime$ radius aperture. Sources from the Sloan Digital Sky Survey (SDSS) Baryon Oscillation Spectroscopic Survey (BOSS) DR15 catalog overlap with 3,700 sq. deg. of sky observed by the Atacama Cosmology Telescope (ACT) from 2008 to 2018 at 150 and 98 GHz (ACT DR5), and 2,089 sq. deg. of internal linear combination component-separated maps combining ACT and $\it{Planck}$ data (ACT DR4). The corresponding optical depths, $\barτ$, which depend on the baryon content of the halos, are estimated using results from cosmological hydrodynamic simulations assuming an AGN feedback radiative cooling model. We estimate the mean mass of the halos in multiple luminosity bins, and compare the tSZ-based $\barτ$ estimates to theoretical predictions of the baryon content for a Navarro-Frenk-White profile. We do the same for $\barτ$ estimates extracted from fits to pairwise baryon momentum measurements of the kinematic Sunyaev-Zel'dovich effect (kSZ) for the same data set obtained in a companion paper. We find that the $\barτ$ estimates from the tSZ measurements in this work and the kSZ measurements in the companion paper agree within $1σ$ for two out of the three disjoint luminosity bins studied, while they differ by 2-3$σ$ in the highest luminosity bin. The optical depth estimates account for one third to all of the theoretically predicted baryon content in the halos across luminosity bins. Potential systematic uncertainties are discussed. The tSZ and kSZ measurements provide a step towards empirical Compton-$\bar{y}$-$\barτ$ relationships to provide new tests of cluster formation and evolution models. △ Less

Submitted 24 August, 2021; v1 submitted 20 January, 2021; originally announced January 2021.

Comments: 19 pages, 9 figures

Journal ref: Phys. Rev. D 104, 043503 (2021)

Concept Design of Low Frequency Telescope for CMB B-mode Polarization satellite LiteBIRD

Authors: Y. Sekimoto, P. A. R. Ade, A. Adler, E. Allys, K. Arnold, D. Auguste, J. Aumont, R. Aurlien, J. Austermann, C. Baccigalupi, A. J. Banday, R. Banerji, R. B. Barreiro, S. Basak, J. Beall, D. Beck, S. Beckman, J. Bermejo, P. de Bernardis, M. Bersanelli, J. Bonis, J. Borrill, F. Boulanger, S. Bounissou, M. Brilenkov , et al. (212 additional authors not shown)

Abstract: LiteBIRD has been selected as JAXA's strategic large mission in the 2020s, to observe the cosmic microwave background (CMB) $B$-mode polarization over the full sky at large angular scales. The challenges of LiteBIRD are the wide field-of-view (FoV) and broadband capabilities of millimeter-wave polarization measurements, which are derived from the system requirements. The possible paths of stray li… ▽ More LiteBIRD has been selected as JAXA's strategic large mission in the 2020s, to observe the cosmic microwave background (CMB) $B$-mode polarization over the full sky at large angular scales. The challenges of LiteBIRD are the wide field-of-view (FoV) and broadband capabilities of millimeter-wave polarization measurements, which are derived from the system requirements. The possible paths of stray light increase with a wider FoV and the far sidelobe knowledge of $-56$ dB is a challenging optical requirement. A crossed-Dragone configuration was chosen for the low frequency telescope (LFT : 34--161 GHz), one of LiteBIRD's onboard telescopes. It has a wide field-of-view ($18^\circ \times 9^\circ$) with an aperture of 400 mm in diameter, corresponding to an angular resolution of about 30 arcminutes around 100 GHz. The focal ratio f/3.0 and the crossing angle of the optical axes of 90$^\circ$ are chosen after an extensive study of the stray light. The primary and secondary reflectors have rectangular shapes with serrations to reduce the diffraction pattern from the edges of the mirrors. The reflectors and structure are made of aluminum to proportionally contract from warm down to the operating temperature at $5\,$K. A 1/4 scaled model of the LFT has been developed to validate the wide field-of-view design and to demonstrate the reduced far sidelobes. A polarization modulation unit (PMU), realized with a half-wave plate (HWP) is placed in front of the aperture stop, the entrance pupil of this system. A large focal plane with approximately 1000 AlMn TES detectors and frequency multiplexing SQUID amplifiers is cooled to 100 mK. The lens and sinuous antennas have broadband capability. Performance specifications of the LFT and an outline of the proposed verification plan are presented. △ Less

Submitted 15 January, 2021; originally announced January 2021.

Comments: 21 pages, 14 figures

Journal ref: SPIE proceedings 1145310 (2020)

In situ Performance of the Low Frequency Arrayfor Advanced ACTPol

Authors: Yaqiong Li, Jason E. Austermann, James A. Beall, Sarah Marie Bruno, Steve K. Choi, Nicholas F. Cothard, Kevin T. Crowley, Shannon M. Duff, Shuay-Pwu Patty Ho, Joseph E. Golec, Gene C. Hilton, Matthew Hasselfield, Johannes Hubmay, Brian J. Koopman, Marius Lungu, Jeff McMahon, Michael D. Niemack, LymanA. Page, Maria Salatino, Sara M. Simon, Suzanne T. Staggs, Jason R. Stevens, Joel N. Ullom, Eve M. Vavagiakis, Yuhan Wang , et al. (2 additional authors not shown)

Abstract: The Advanced Atacama Cosmology Telescope Polarimeter (AdvACT) \cite{thornton} is an upgrade for the Atacama Cosmology Telescope using Transition Edge Sensor (TES) detector arrays to measure cosmic microwave background (CMB) temperature and polarization anisotropies in multiple frequencies. The low frequency (LF) array was deployed early 2020. It consists of 292 TES bolometers observing in two band… ▽ More The Advanced Atacama Cosmology Telescope Polarimeter (AdvACT) \cite{thornton} is an upgrade for the Atacama Cosmology Telescope using Transition Edge Sensor (TES) detector arrays to measure cosmic microwave background (CMB) temperature and polarization anisotropies in multiple frequencies. The low frequency (LF) array was deployed early 2020. It consists of 292 TES bolometers observing in two bands centered at 27 GHz and 39 GHz. At these frequencies, it is sensitive to synchrotron radiation from our galaxy as well as to the CMB, and complements the AdvACT arrays operating at 90, 150 and 230 GHz. We present the initial LF array on-site characterization, including the time constant, optical efficiency and array sensitivity. △ Less

Submitted 12 January, 2021; v1 submitted 7 January, 2021; originally announced January 2021.

Design and pre-flight performance of SPIDER 280 GHz receivers

Authors: E. C. Shaw, P. A. R. Ade, S. Akers, M. Amiri, J. Austermann, J. Beall, D. T. Becker, S. J. Benton, A. S. Bergman, J. J. Bock, J. R. Bond, S. A. Bryan, H. C. Chiang, C. R. Contaldi, R. S. Domagalski, O. Doré, S. M. Duff, A. J. Duivenvoorden, H. K. Eriksen, M. Farhang, J. P. Filippini, L. M. Fissel, A. A. Fraisse, K. Freese, M. Galloway , et al. (57 additional authors not shown)

Abstract: In this work we describe upgrades to the Spider balloon-borne telescope in preparation for its second flight, currently planned for December 2021. The Spider instrument is optimized to search for a primordial B-mode polarization signature in the cosmic microwave background at degree angular scales. During its first flight in 2015, Spider mapped ~10% of the sky at 95 and 150 GHz. The payload for th… ▽ More In this work we describe upgrades to the Spider balloon-borne telescope in preparation for its second flight, currently planned for December 2021. The Spider instrument is optimized to search for a primordial B-mode polarization signature in the cosmic microwave background at degree angular scales. During its first flight in 2015, Spider mapped ~10% of the sky at 95 and 150 GHz. The payload for the second Antarctic flight will incorporate three new 280 GHz receivers alongside three refurbished 95- and 150 GHz receivers from Spider's first flight. In this work we discuss the design and characterization of these new receivers, which employ over 1500 feedhorn-coupled transition-edge sensors. We describe pre-flight laboratory measurements of detector properties, and the optical performance of completed receivers. These receivers will map a wide area of the sky at 280 GHz, providing new information on polarized Galactic dust emission that will help to separate it from the cosmological signal. △ Less

Submitted 22 December, 2020; originally announced December 2020.

Comments: 13 pages, 8 figures; as published in the conference proceedings for SPIE Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X (2020)

Journal ref: "Design and pre-flight performance of SPIDER 280 GHz receivers," Proc. SPIE 11453, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X, 114532F (13 December 2020)

The Simons Observatory: Magnetic Sensitivity Measurements of Microwave SQUID Multiplexers

Authors: Eve M. Vavagiakis, Zeeshan Ahmed, Aamir Ali, Kam Arnold, Jason Austermann, Sarah Marie Bruno, Steve K. Choi, Jake Connors, Nicholas F. Cothard, Simon Dicker, Brad Dober, Shannon Duff, Valentina Fanfani, Erin Healy, Shawn Henderson, Shuay-Pwu Patty Ho, Duc-Thuong Hoang, Gene Hilton, Johannes Hubmayr, Nicoletta Krachmalnicoff, Yaqiong Li, John Mates, Heather McCarrick, Federico Nati, Michael Niemack , et al. (8 additional authors not shown)

Abstract: The Simons Observatory (SO) will be a cosmic microwave background (CMB) survey experiment with three small-aperture telescopes and one large-aperture telescope, which will observe from the Atacama Desert in Chile. In total, SO will field $\sim$70,000 transition-edge sensor (TES) bolometers in six spectral bands centered between 27 and 280 GHz in order to achieve the sensitivity necessary to measur… ▽ More The Simons Observatory (SO) will be a cosmic microwave background (CMB) survey experiment with three small-aperture telescopes and one large-aperture telescope, which will observe from the Atacama Desert in Chile. In total, SO will field $\sim$70,000 transition-edge sensor (TES) bolometers in six spectral bands centered between 27 and 280 GHz in order to achieve the sensitivity necessary to measure or constrain numerous cosmological quantities. The SO Universal Focal Plane Modules (UFMs) each contain a 150 mm diameter TES detector array, horn or lenslet optical coupling, cold readout components, and magnetic shielding. SO will use a microwave SQUID multiplexing ($μ$MUX) readout at an initial multiplexing factor of $\sim$1000; the cold (100 mK) readout components are packaged in a $μ$MUX readout module, which is part of the UFM, and can also be characterized independently. The 100 mK stage TES bolometer arrays and microwave SQUIDs are sensitive to magnetic fields, and their measured response will vary with the degree to which they are magnetically shielded. We present measurements of the magnetic pickup of test microwave SQUID multiplexers as a study of various shielding configurations for the Simons Observatory. We discuss how these measurements motivated the material choice and design of the UFM magnetic shielding. △ Less

Submitted 8 December, 2020; originally announced December 2020.

Comments: 5 pages, 6 figures, conference proceedings submitted to IEEE Transactions on Applied Superconductivity

Journal ref: IEEE Transactions on Applied Superconductivity, vol. 31, issue 5, id. 3069294 (Aug 2021)

Characterization, deployment, and in-flight performance of the BLAST-TNG cryogenic receiver

Authors: Ian Lowe, Peter A. R. Ade, Peter C. Ashton, Jason E. Austermann, Gabriele Coppi, Erin G. Cox, Mark J. Devlin, Bradley J. Dober, Valentina Fanfani, Laura M. Fissel, Nicholas Galitzki, Jiansong Gao, Samuel Gordon, Christopher E. Groppi, Gene C. Hilton, Johannes Hubmayr, Jeffrey Klein, Dale Li, Nathan P. Lourie, Hamdi Mani, Philip Mauskopf, Christopher McKenney, Federico Nati, Giles Novak, Giampaolo Pisano , et al. (8 additional authors not shown)

Abstract: The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter polarimeter designed to map interstellar dust and galactic foregrounds at 250, 350, and 500 microns during a 24-day Antarctic flight. The BLAST-TNG detector arrays are comprised of 918, 469, and 272 MKID pixels, respectively. The pixels are formed from two orthogonally oriented, crossed, linear-… ▽ More The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter polarimeter designed to map interstellar dust and galactic foregrounds at 250, 350, and 500 microns during a 24-day Antarctic flight. The BLAST-TNG detector arrays are comprised of 918, 469, and 272 MKID pixels, respectively. The pixels are formed from two orthogonally oriented, crossed, linear-polarization sensitive MKID antennae. The arrays are cooled to sub 300mK temperatures and stabilized via a closed cycle $^3$He sorption fridge in combination with a $^4$He vacuum pot. The detectors are read out through a combination of the second-generation Reconfigurable Open Architecture Computing Hardware (ROACH2) and custom RF electronics designed for BLAST-TNG. The firmware and software designed to readout and characterize these detectors was built from scratch by the BLAST team around these detectors, and has been adapted for use by other MKID instruments such as TolTEC and OLIMPO. We present an overview of these systems as well as in-depth methodology of the ground-based characterization and the measured in-flight performance. △ Less

Submitted 12 January, 2021; v1 submitted 2 December, 2020; originally announced December 2020.

Comments: Presented at SPIE Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X, December 13-18, 2020

Journal ref: Proc. SPIE 11453, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X, 1145304 (13 December 2020)

In-flight performance of the BLAST-TNG telescope platform

Authors: Gabriele Coppi, Peter A. R. Ade, Peter C. Ashton, Jason E. Austermann, Erin G. Cox, Mark J. Devlin, Bradley J. Dober, Valentina Fanfani, Laura M. Fissel, Nicholas Galitzki, Jiansong Gao, Samuel Gordon, Christopher E. Groppi, Gene C. Hilton, Johannes Hubmayr, Jeffrey Klein, Dale Li, Nathan P. Lourie, Ian Lowe, Hamdi Mani, Philip Mauskopf, Christopher McKenney, Federico Nati, Giles Novak, Giampaolo Pisano , et al. (8 additional authors not shown)

Abstract: The Next Generation Balloon-Borne Large Aperture Submillimeter Telescope (BLAST-TNG) was a unique instrument for characterizing the polarized submillimeter sky at high-angular resolution. BLAST-TNG flew from the Long Duration Balloon Facility in Antarctica in January 2020. Despite the short flight duration, the instrument worked very well and is providing significant information about each subsyst… ▽ More The Next Generation Balloon-Borne Large Aperture Submillimeter Telescope (BLAST-TNG) was a unique instrument for characterizing the polarized submillimeter sky at high-angular resolution. BLAST-TNG flew from the Long Duration Balloon Facility in Antarctica in January 2020. Despite the short flight duration, the instrument worked very well and is providing significant information about each subsystem that will be invaluable for future balloon missions. In this contribution, we discuss the performance of telescope and gondola. △ Less

Submitted 2 January, 2021; v1 submitted 2 December, 2020; originally announced December 2020.

Comments: Submitted to SPIE Astronomical Telescopes + Instrumentation, Ground-based and Airborne Telescopes VIII

Journal ref: Proc. SPIE 11445, Ground-based and Airborne Telescopes VIII, 2020

A Microwave SQUID Multiplexer Optimized for Bolometric Applications

Authors: B. Dober, Z. Ahmed, K. Arnold, D. T. Becker, D. A. Bennett, J. A. Connors, A. Cukierman, J. M. D'Ewart, S. M. Duff, J. E. Dusatko, J. C. Frisch, J. D. Gard, S. W. Henderson, R. Herbst, G. C. Hilton, J. Hubmayr, Y. Li, J. A. B. Mates, H. McCarrick, C. D Reintsema, M. Silva-Feaver, L. Ruckman, J. N. Ullom, L. R. Vale, D. D. Van Winkle , et al. (5 additional authors not shown)

Abstract: A microwave SQUID multiplexer ($μ$MUX) has been optimized for coupling to large arrays of superconducting transition-edge sensor (TES) bolometers. We present the scalable cryogenic multiplexer chip design in a 1820-channel multiplexer configuration for the 4-8 GHz rf band. The key metrics of yield, sensitivity, and crosstalk are determined through measurements of 455 readout channels, which span 4… ▽ More A microwave SQUID multiplexer ($μ$MUX) has been optimized for coupling to large arrays of superconducting transition-edge sensor (TES) bolometers. We present the scalable cryogenic multiplexer chip design in a 1820-channel multiplexer configuration for the 4-8 GHz rf band. The key metrics of yield, sensitivity, and crosstalk are determined through measurements of 455 readout channels, which span 4-5 GHz. The median white-noise level is 45 pA/$\sqrt{\textrm{Hz}}$, evaluated at 2 Hz, with a 1/f knee $\leq$ 20 mHz after common-mode subtraction. The white-noise level decreases the sensitivity of a TES bolometer optimized for detection of the cosmic microwave background at 150 GHz by only 3%. The measured crosstalk between any channel pair is $\leq$ 0.3%. △ Less

Submitted 19 January, 2021; v1 submitted 15 October, 2020; originally announced October 2020.

Comments: 6 pages, 5 figures

The Atacama Cosmology Telescope: A Catalog of > 4000 Sunyaev-Zel'dovich Galaxy Clusters

Authors: M. Hilton, C. Sifón, S. Naess, M. Madhavacheril, M. Oguri, E. Rozo, E. Rykoff, T. M. C. Abbott, S. Adhikari, M. Aguena, S. Aiola, S. Allam, S. Amodeo, A. Amon, J. Annis, B. Ansarinejad, C. Aros-Bunster, J. E. Austermann, S. Avila, D. Bacon, N. Battaglia, J. A. Beall, D. T. Becker, G. M. Bernstein, E. Bertin , et al. (124 additional authors not shown)

Abstract: We present a catalog of 4195 optically confirmed Sunyaev-Zel'dovich (SZ) selected galaxy clusters detected with signal-to-noise > 4 in 13,211 deg$^2$ of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multi-frequency matched filter to 98 and 150 GHz maps constructed from ACT observations obtained from 2008-2018, and confirmed using deep, wide-a… ▽ More We present a catalog of 4195 optically confirmed Sunyaev-Zel'dovich (SZ) selected galaxy clusters detected with signal-to-noise > 4 in 13,211 deg$^2$ of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multi-frequency matched filter to 98 and 150 GHz maps constructed from ACT observations obtained from 2008-2018, and confirmed using deep, wide-area optical surveys. The clusters span the redshift range 0.04 < z < 1.91 (median z = 0.52). The catalog contains 222 z > 1 clusters, and a total of 868 systems are new discoveries. Assuming an SZ-signal vs. mass scaling relation calibrated from X-ray observations, the sample has a 90% completeness mass limit of M500c > 3.8 x 10$^{14}$ MSun, evaluated at z = 0.5, for clusters detected at signal-to-noise ratio > 5 in maps filtered at an angular scale of 2.4'. The survey has a large overlap with deep optical weak-lensing surveys that are being used to calibrate the SZ-signal mass-scaling relation, such as the Dark Energy Survey (4566 deg$^2$), the Hyper Suprime-Cam Subaru Strategic Program (469 deg$^2$), and the Kilo Degree Survey (825 deg$^2$). We highlight some noteworthy objects in the sample, including potentially projected systems; clusters with strong lensing features; clusters with active central galaxies or star formation; and systems of multiple clusters that may be physically associated. The cluster catalog will be a useful resource for future cosmological analyses, and studying the evolution of the intracluster medium and galaxies in massive clusters over the past 10 Gyr. △ Less

Submitted 2 December, 2020; v1 submitted 23 September, 2020; originally announced September 2020.

Comments: 35 pages, 27 figures, accepted for publication in ApJS; v1.0 catalogs will be available from LAMBDA https://lambda.gsfc.nasa.gov/product/act/actpol_prod_table.cfm; v1.0 catalogs available from https://astro.ukzn.ac.za/~mjh/ACTDR5/v1.0/ until then