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Precision Kinematic Sunyaev--Zel'dovich Measurements Across Halo Mass and Redshift with DESI DR2 and ACT DR6: Part I. Luminous Red Galaxies
Authors:
F. J. Qu,
B. Ried Guachalla,
E. Schaan,
B. Hadzhiyska,
S. Ferraro,
J. Aguilar,
S. Ahlen,
A. Baleato Lizancos,
D. Bianchi,
D. Brooks,
R. Canning,
F. J. Castander,
E. Chaussidon,
T. Claybaugh,
A. Cuceu,
A. de la Macorra,
B. Dey,
P. Doel,
A. Font-Ribera,
J. E. Forero-Romero,
E. Gaztañaga,
S. Gontcho A Gontcho,
G. Gutierrez,
H. K. Herrera-Alcantar,
K. Honscheid
, et al. (29 additional authors not shown)
Abstract:
We present the most precise measurements of the kinetic Sunyaev-Zel'dovich (kSZ) effect around luminous red galaxies to date, detecting the signal at $18σ$ significance in both harmonic and configuration space. Our analysis cross-correlates 2.4 million spectroscopic LRGs from the Dark Energy Spectroscopic Instrument (DESI) DR2 sample with Data Release 6 (DR6) of the Atacama Cosmology Telescope (AC…
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We present the most precise measurements of the kinetic Sunyaev-Zel'dovich (kSZ) effect around luminous red galaxies to date, detecting the signal at $18σ$ significance in both harmonic and configuration space. Our analysis cross-correlates 2.4 million spectroscopic LRGs from the Dark Energy Spectroscopic Instrument (DESI) DR2 sample with Data Release 6 (DR6) of the Atacama Cosmology Telescope (ACT). We develop a novel harmonic-space cross-correlation approach using momentum-weighted kSZ templates, yielding nearly uncorrelated bandpowers within a framework consistent with other large-scale structure analyses. By incorporating the LRG halo occupation distribution (HOD) and its uncertainty, we convert measured galaxy gas profiles into halo gas profiles and provide generalized Navarro-Frenk-White (GNFW) fitting profiles, providing empirical targets for tuning feedback efficiency in hydrodynamical simulations and for baryonic modeling in large-scale structure analyses. We find strong evidence that gas profiles do not trace dark matter, providing direct evidence for gas redistribution beyond gravitational collapse. Comparing to hydrodynamical simulations, our measurements favor feedback efficiencies exceeding those in the Battaglia profile, suggesting more efficient gas ejection in group-scale halos than previously predicted. Splitting by redshift, we detect the kSZ signal at SNR $\approx 5$--$10$ in each of four bins and find amplitude evolution consistent with the expected decline in mean halo mass at fixed comoving number density. Splitting by stellar mass, we study the scaling of kSZ amplitude with galaxy properties. Together with BGS and ELG measurements in Paper II, these results span $0.1 \lesssim z \lesssim 1.6$ across three galaxy populations, demonstrating the potential of spectroscopic kSZ to map circumgalactic gas and constrain baryonic feedback.
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Submitted 21 April, 2026;
originally announced April 2026.
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Estimation and mitigation of foregrounds in projected kSZ velocity reconstruction
Authors:
Carmen Embil Villagra,
Fiona McCarthy,
Antón Baleato Lizancos,
Blake D. Sherwin,
Anthony Challinor
Abstract:
The kSZ effect has recently emerged as a powerful probe for precision cosmology through its ability to reconstruct the large-scale velocity field. In particular, the kSZ-reconstructed velocity-galaxy cross-correlation is sensitive to signatures of primordial non-Gaussianity through its imprint on the galaxy bias. The kSZ velocity reconstruction is performed using small-scale information from CMB t…
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The kSZ effect has recently emerged as a powerful probe for precision cosmology through its ability to reconstruct the large-scale velocity field. In particular, the kSZ-reconstructed velocity-galaxy cross-correlation is sensitive to signatures of primordial non-Gaussianity through its imprint on the galaxy bias. The kSZ velocity reconstruction is performed using small-scale information from CMB temperature and galaxy overdensities. As the sensitivity of these measurements improves, systematic effects such as extragalactic foreground contamination present in CMB maps become increasingly important. We present a study of foreground biases to the kSZ-reconstructed velocity-galaxy cross-correlation. We derive the relevant foreground contributions from the thermal Sunyaev-Zel'dovich effect and the cosmic infrared background, modeling them using a halo model description of the dominant one- and two-halo terms. We compare our analytic predictions to measurements obtained using ACT DR6 temperature maps and DESI Legacy Imaging Survey galaxies, finding qualitative agreement. We introduce a parity-odd estimator constructed from antisymmetric combinations of tomographic velocity-galaxy correlations and show analytically that, under the Limber approximation, this estimator entirely cancels the foreground contamination while preserving the full cosmological signal without loss of signal-to-noise. Finally, we apply this parity-odd estimator to the data combination mentioned above and show that the fit to the velocity-galaxy correlation is dramatically improved compared to the analysis without mitigation; our estimator detects the signal at 11$σ$, with an amplitude consistent with recent studies.
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Submitted 30 March, 2026;
originally announced March 2026.
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An analytic approximation to the covariance between pre- and post-reconstruction galaxy two-point statistics
Authors:
M. Maus,
A. Baleato Lizancos,
M. White,
A. de Mattia,
S. Chen
Abstract:
We present a simple analytic approximation for the covariance between pre-reconstruction galaxy power spectrum measurements and post-reconstruction two-point correlation functions. This cross-covariance is essential for joint analyses that combine full-shape clustering information with baryon acoustic oscillation (BAO) measurements, as commonly performed in modern spectroscopic surveys. Our model…
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We present a simple analytic approximation for the covariance between pre-reconstruction galaxy power spectrum measurements and post-reconstruction two-point correlation functions. This cross-covariance is essential for joint analyses that combine full-shape clustering information with baryon acoustic oscillation (BAO) measurements, as commonly performed in modern spectroscopic surveys. Our model builds on the disconnected contribution to the covariance and accounts for the damping of correlations due to the BAO reconstruction process. We validate our analytic prescription against numerical simulations from the Dark Energy Spectroscopic Instrument (DESI), testing both idealized cubic geometries and realistic survey configurations including complex footprints and fiber assignment effects. Despite neglecting survey window functions in the analytic calculation, we find excellent agreement with simulation-based covariances and demonstrate that cosmological parameter constraints are virtually unchanged when using our approximation. Our results show that the pre-post cross-covariance is sufficiently small that even approximate treatments are adequate for cosmological inference, opening a pathway toward fully analytic covariance matrices for next-generation galaxy surveys.
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Submitted 28 May, 2026; v1 submitted 12 February, 2026;
originally announced February 2026.
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Constraining primordial non-Gaussianity from DESI DR1 quasars and Planck PR4 CMB Lensing
Authors:
Sofia Chiarenza,
Alex Krolewski,
Marco Bonici,
Edmond Chaussidon,
Roger de Belsunce,
Will Percival,
Jessica Nicole Aguilar,
Steven Ahlen,
Anton Baleato Lizancos,
Davide Bianchi,
David Brooks,
Todd Claybaugh,
Andrei Cuceu,
Kyle Dawson,
Axel de la Macorra,
Peter Doel,
Simone Ferraro,
Andreu Font-Ribera,
Jaime E. Forero-Romero,
Enrique Gaztañaga,
Satya Gontcho A Gontcho,
Gaston Gutierrez,
Hiram K. Herrera-Alcantar,
Klaus Honscheid,
Dragan Huterer
, et al. (32 additional authors not shown)
Abstract:
We present the first measurement of local-type primordial non-Gaussianity from the cross-correlation between $1.2$ million spectroscopically confirmed quasars from the first data release (DR1) of the Dark Energy Spectroscopic Instrument (DESI) and the Planck PR4 CMB lensing reconstructions. The analysis is performed in three tomographic redshift bins covering $0.8 < z < 3.5$, covering a sky fracti…
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We present the first measurement of local-type primordial non-Gaussianity from the cross-correlation between $1.2$ million spectroscopically confirmed quasars from the first data release (DR1) of the Dark Energy Spectroscopic Instrument (DESI) and the Planck PR4 CMB lensing reconstructions. The analysis is performed in three tomographic redshift bins covering $0.8 < z < 3.5$, covering a sky fraction of $\sim 20\%$. We adopt a catalog-based pseudo-$C_\ell$ estimator and apply linear imaging weights validated on noiseless mocks. Compared to previous analyses using photometric quasar samples, our results benefit from the high purity of the DESI spectroscopic sample, the reduced noise of PR4 lensing, and the absence of excess large-scale power in the spectroscopic quasar auto-correlation. Fitting simultaneously for the non-Gaussianity parameter $f_{\mathrm{NL}}$ and the linear bias amplitude in each redshift bin, we obtain $f_{\mathrm{NL}} = 2^{+28}_{-34}$ for a response parameter $p=1.6$, and $f_{\mathrm{NL}} = 6^{+20}_{-24}$ for $p=1.0$. These results improve the constraints on $f_{\mathrm{NL}}$ by $\sim 35\%$ compared to the previous analysis based on the Legacy Imaging Survey DR9. Additionally, we derive an optimal weighting scheme to maximize the constraining power. In this case, and assuming $p=1.6$, we obtain $f_\mathrm{NL}=19^{+25}_{-31}$. Our results demonstrate the statistical power of DESI quasars for probing inflationary physics, and highlight the promise of future DESI data releases.
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Submitted 15 April, 2026; v1 submitted 19 December, 2025;
originally announced December 2025.
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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…
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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.
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Submitted 17 December, 2025;
originally announced December 2025.
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The Atacama Cosmology Telescope: $B$-mode delensing with DR6 data and external tracers of large-scale structure
Authors:
Emilie Hertig,
Antón Baleato Lizancos,
Frank J. Qu,
J. Richard Bond,
Erminia Calabrese,
Anthony Challinor,
Mark J. Devlin,
Jo Dunkley,
Thibaut Louis,
Mathew S. Madhavacheril,
Toshiya Namikawa,
Lyman A. Page,
Neelima Sehgal,
Blake Sherwin,
Cristóbal Sifón,
Suzanne T. Staggs,
Edward J. Wollack
Abstract:
Large-scale $B$-mode polarization of the cosmic microwave background (CMB) is a prime target for current and future experiments in search of primordial gravitational waves (PGW). With increasingly sensitive instruments being deployed, secondary $B$-modes induced by the weak gravitational lensing of CMB photons are becoming an important limitation and need to be removed, a process known as delensin…
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Large-scale $B$-mode polarization of the cosmic microwave background (CMB) is a prime target for current and future experiments in search of primordial gravitational waves (PGW). With increasingly sensitive instruments being deployed, secondary $B$-modes induced by the weak gravitational lensing of CMB photons are becoming an important limitation and need to be removed, a process known as delensing. In this work, we combine internally reconstructed CMB lensing maps from the Atacama Cosmology Telescope (ACT) DR6 with galaxy samples from unWISE and a map of the cosmic infrared background (CIB) fluctuations from Planck to produce a well-correlated tracer of the CMB lensing field. Our co-added tracer, shown to be 55-85% correlated with the true lensing convergence at multipoles $L \leq 2000$, is then convolved with ACT DR6 $E$-mode polarization to yield a template of the lensing $B$-modes. We assess its performance on a wide range of scales by using it to delens ACT DR6 and Planck $B$-modes over 23% of the sky, removing around 39% of the lensing power at $100\leq l \leq 1500$ and 47% at $30 \leq l \leq 300$, respectively. Our template achieves the highest delensing efficiency to date and will be useful for the analysis of early polarization maps from the Simons Observatory (SO). We finally outline prospects for further improvements by including additional large-scale structure tracers from upcoming cosmological surveys.
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Submitted 26 November, 2025;
originally announced November 2025.
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Full calibration of the tomographic redshift distribution from the HSC PDR3 Shape Catalog with DESI
Authors:
J. Choppin de Janvry,
S. Gontcho A Gontcho,
U. Seljak,
A. Baleato Lizancos,
E. Chaussidon,
W. d'Assignies,
J. DeRose,
S. Heydenreich,
E. Paillas,
D. Valcin,
T. Zhang,
J. Aguilar,
S. Ahlen,
D. Bianchi,
D. Brooks,
F. J. Castander,
T. Claybaugh,
A. Cuceu,
A. de la Macorra,
P. Doel,
S. Ferraro,
A. Font-Ribera,
J. E. Forero-Romero,
E. Gaztañaga,
G. Gutierrez
, et al. (31 additional authors not shown)
Abstract:
The calibration of tomographic redshift distributions is essential for cosmological analysis of weak lensing data. In this work, we calibrate all four tomographic bins of the Hyper Suprime Camera (HSC) weak lensing catalog with the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 and 2 using the clustering redshifts technique. We include z > 1.2 redshift sources such as emission line gal…
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The calibration of tomographic redshift distributions is essential for cosmological analysis of weak lensing data. In this work, we calibrate all four tomographic bins of the Hyper Suprime Camera (HSC) weak lensing catalog with the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 and 2 using the clustering redshifts technique. We include z > 1.2 redshift sources such as emission line galaxies (ELG) and quasars (QSO) sources in our calibration, which were not available in the previous HSC calibration (Rau et al. 2022), allowing a complete calibration of all the redshift bins. We find the first tomographic bin exhibits a small shift towards low redshifts. The second bin is in good agreement with the photometric calibration, while third and fourth bin exhibit a shift towards higher redshifts. However, these shifts are considerably smaller than the shifts obtained in the HSC Year 3 cosmic shear analyses. We evaluate the impact of galaxy bias and magnification effects from all the samples on the measurements, finding them to be small, and we propose corrections to reduce them further. Specifically, we relax the assumption of linear bias and only assume no redshift evolution of the cross-correlation coefficient, allowing us to leverage smaller clustering scales. We model the redshift distributions with splines and compare our results to previous analyses as well as to other parameterizations found in literature. For the two high-redshift tomographic bins, we find the shifts to higher redshifts with respect to the measurements performed in Rau+2022 to be $Δz_3=-0.039^{+0.020}_{-0.021}$ and $Δz_4=-0.048^{+0.012}_{-0.012}$.
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Submitted 30 March, 2026; v1 submitted 22 November, 2025;
originally announced November 2025.
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Delensing CMB B-modes using galaxy surveys: the effect of galaxy bias and matter clustering non-linearities
Authors:
Shengzhu Wang,
Antón Baleato Lizancos,
José Luis Bernal
Abstract:
The B-mode of polarization of the CMB is a uniquely powerful probe of gravitational waves produced in the very early Universe. But searches for primordial B-mode anisotropies must contend with gravitational lensing, which induces late-time B-modes not associated with gravitational waves. These lensing B-modes can be removed -- i.e., delensed -- using observations of the E-modes and a proxy of the…
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The B-mode of polarization of the CMB is a uniquely powerful probe of gravitational waves produced in the very early Universe. But searches for primordial B-mode anisotropies must contend with gravitational lensing, which induces late-time B-modes not associated with gravitational waves. These lensing B-modes can be removed -- i.e., delensed -- using observations of the E-modes and a proxy of the matter fluctuations along the line of sight that caused the deflections. The number density and redshift reach of galaxy surveys such as the upcoming Rubin observatory offer attractive prospects for using them to delens B-mode data from CMB experiments such as the Simons Observatory, LiteBIRD or CMB-S4. However, stochasticity and non-linear galaxy bias may in principle decorrelate the galaxy field from the matter distribution responsible for the lensing effect, thus hindering efforts to delens B-modes. In addition, non-linear gravitational evolution and bias introduce non-Gaussianities in the large-scale structure which further complicate the modelling. We quantify these effects by populating an N-body simulation with a magnitude-limited, photometric sample of galaxies similar to Rubin's gold selection, and using them to delens CMB maps lensed by the same matter distribution. We find that pipelines that treat the galaxy overdensity as a Gaussian field will incur negligible bias on the inferred tensor-to-scalar ratio, r. Moreover, we show that even in a highly conservative scenario where only the linear bias of the galaxies can be determined, the bias on r arising from this simplification is well within statistical uncertainties for a cosmic-variance limited scenario where Rubin-like galaxies are used for delensing.
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Submitted 25 February, 2026; v1 submitted 7 July, 2025;
originally announced July 2025.
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A halo model of extragalactic contamination to CMB lensing, delensing, and cross-correlations
Authors:
A. Baleato Lizancos,
W. Coulton,
A. Challinor,
B. D. Sherwin,
Y. Mehta
Abstract:
CMB lensing reconstructions are a sensitive probe of the growth of structure across cosmic time and a key tool to sharpen investigations of the very early Universe via delensing. At present, a large fraction of this information is drawn from the temperature anisotropies, which are ultimately also the most informative when reconstructing lenses on arcminute scales and smaller. But extragalactic for…
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CMB lensing reconstructions are a sensitive probe of the growth of structure across cosmic time and a key tool to sharpen investigations of the very early Universe via delensing. At present, a large fraction of this information is drawn from the temperature anisotropies, which are ultimately also the most informative when reconstructing lenses on arcminute scales and smaller. But extragalactic foreground emission from galaxies and clusters can contaminate these reconstructions, limiting our ability to use information from small-scale temperature anisotropies. We develop analytic predictions of the biases from the thermal Sunyaev-Zeldovich and cosmic infrared background to CMB lensing auto- and cross-correlations with low-redshift matter tracers, as well as B-mode delensing, based on a halo model for the dominant one- and two-halo contributions to the relevant foreground bi- and tri-spectra. The method is flexible enough to allow variations in cosmology, astrophysical modeling, experimental configurations and analysis choices, thus enabling an improved understanding of the uncertainties involved in current mitigation strategies. We find that the shape of the bias relative to the CMB lensing auto-spectrum signal is remarkably insensitive to changes in cosmological and astrophysical parameter values. On the other hand, the shape appears to depend on $Ω_m$ for cross-correlations with low-redshift galaxies. We also clarify the ranges of redshifts and masses that simulations need to resolve in order to capture these effects accurately. Our code, CosmoBLENDER, is made publicly available.
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Submitted 26 February, 2026; v1 submitted 4 July, 2025;
originally announced July 2025.
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A joint analysis of 3D clustering and galaxy x CMB-lensing cross-correlations with DESI DR1 galaxies
Authors:
M. Maus,
M. White,
N. Sailer,
A. Baleato Lizancos,
S. Ferraro,
S. Chen,
J. DeRose,
J. Aguilar,
S. Ahlen,
S. BenZvi,
D. Bianchi,
D. Brooks,
E. Burtin,
F. J. Castander,
E. Chaussidon,
T. Claybaugh,
A. Cuceu,
A. de la Macorra,
A. de Mattia,
P. Doel,
A. Font-Ribera,
J. E. Forero-Romero,
E. Gaztañaga,
S. Gontcho A Gontcho,
G. Gutierrez
, et al. (36 additional authors not shown)
Abstract:
The spectroscopic data from DESI Data Release 1 (DR1) galaxies enables the analysis of 3D clustering by fitting galaxy power spectra and reconstructed correlation functions in redshift space. Given low measurements of the amplitude of structure from cosmic shear at $z\sim1$, redshift space distortions (RSD) + Baryon Acoustic Oscillation (BAO) signals from DESI galaxies combined with weak lensing c…
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The spectroscopic data from DESI Data Release 1 (DR1) galaxies enables the analysis of 3D clustering by fitting galaxy power spectra and reconstructed correlation functions in redshift space. Given low measurements of the amplitude of structure from cosmic shear at $z\sim1$, redshift space distortions (RSD) + Baryon Acoustic Oscillation (BAO) signals from DESI galaxies combined with weak lensing can break degeneracies and provide a tight alternative constraint on the $z\sim1$ amplitude of structure. In this paper we perform joint analyses that combine full-shape + post-reconstruction information from the DESI DR1 BGS and LRG samples along with angular cross-correlations with Planck PR4 and ACT DR6 CMB lensing maps. We show that adding galaxy-lensing cross-correlations tightens clustering amplitude constraints, improving $σ_8$ uncertainties by $\sim 40\%$ over RSD+BAO alone. We also include angular galaxy-galaxy and galaxy-lensing spectra using photometric samples from the DESI Legacy Survey to further improve constraints. Our headline results are $σ_8 = 0.803\pm 0.017$, $Ω_{\rm m} = 0.3037\pm 0.0069$, and $S_8 = 0.808\pm 0.017$. Given DESI's preference for higher $σ_8$ compared to lower values from BOSS, we perform a catalog-level comparison of LRG samples from both surveys. We test sensitivity to dark energy assumptions by relaxing our $Λ$CDM prior and allowing for evolving dark energy via the $w_0-w_a$ parameterization. We find our $S_8$ constraints to be relatively unchanged despite a $~3.5σ$ tension with the cosmological constant model when combining with the Union3 supernova likelihood. Finally we test general relativity (GR) by allowing the gravitational slip parameter ($γ$) to vary, and find $γ= 1.17\pm0.11$ in mild ($\sim1.5σ$) tension with the GR value of $1.0$.
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Submitted 15 October, 2025; v1 submitted 26 May, 2025;
originally announced May 2025.
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Enhancing DESI DR1 Full-Shape analyses using HOD-informed priors
Authors:
Hanyu Zhang,
Marco Bonici,
Antoine Rocher,
Will J. Percival,
Arnaud de Mattia,
Jessica Nicole Aguilar,
Steven Ahlen,
Otávio Alves,
Alejandro Aviles,
Anton Baleato Lizancos,
Davide Bianchi,
David Brooks,
Andrei Cuceu,
Axel de la Macorra,
Peter Doel,
Simone Ferraro,
Nathan Findlay,
Andreu Font-Ribera,
Daniel Felipe Forero Sánchez,
Jaime E. Forero-Romero,
Satya Gontcho A Gontcho,
Gaston Gutierrez,
ChangHoon Hahn,
Cullan Howlett,
Mustapha Ishak
, et al. (35 additional authors not shown)
Abstract:
We present an analysis of DESI Data Release 1 (DR1) that incorporates Halo Occupation Distribution (HOD)-informed priors into Full-Shape (FS) modeling of the power spectrum based on cosmological perturbation theory (PT). By leveraging physical insights from the galaxy-halo connection, these HOD-informed priors on nuisance parameters substantially mitigate projection effects in extended cosmologica…
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We present an analysis of DESI Data Release 1 (DR1) that incorporates Halo Occupation Distribution (HOD)-informed priors into Full-Shape (FS) modeling of the power spectrum based on cosmological perturbation theory (PT). By leveraging physical insights from the galaxy-halo connection, these HOD-informed priors on nuisance parameters substantially mitigate projection effects in extended cosmological models that allow for dynamical dark energy. The resulting credible intervals now encompass the posterior maximum from the baseline analysis using gaussian priors, eliminating a significant posterior shift observed in baseline studies. In the $Λ$CDM framework, a combined DESI DR1 FS information and constraints from the DESI DR1 baryon acoustic oscillations (BAO)-including Big Bang Nucleosynthesis (BBN) constraints and a weak prior on the scalar spectral index-yields $Ω_{\rm m} = 0.2994\pm 0.0090$ and $σ_8 = 0.836^{+0.024}_{-0.027}$, representing improvements of approximately 4% and 23% over the baseline analysis, respectively. For the $w_0w_a$CDM model, our results from various data combinations are highly consistent, with all configurations converging to a region with $w_0 > -1$ and $w_a < 0$. This convergence not only suggests intriguing hints of dynamical dark energy but also underscores the robustness of our HOD-informed prior approach in delivering reliable cosmological constraints.
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Submitted 14 April, 2025;
originally announced April 2025.
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Data Release 1 of the Dark Energy Spectroscopic Instrument
Authors:
DESI Collaboration,
M. Abdul Karim,
A. G. Adame,
D. Aguado,
J. Aguilar,
S. Ahlen,
S. Alam,
G. Aldering,
D. M. Alexander,
R. Alfarsy,
L. Allen,
C. Allende Prieto,
O. Alves,
A. Anand,
U. Andrade,
E. Armengaud,
S. Avila,
A. Aviles,
H. Awan,
S. Bailey,
A. Baleato Lizancos,
O. Ballester,
A. Bault,
J. Bautista,
R. Bean
, et al. (285 additional authors not shown)
Abstract:
In 2021 May the Dark Energy Spectroscopic Instrument (DESI) collaboration began a 5-year spectroscopic redshift survey to produce a detailed map of the evolving three-dimensional structure of the universe between $z=0$ and $z\approx4$. DESI's principle scientific objectives are to place precise constraints on the equation of state of dark energy, the gravitationally driven growth of large-scale st…
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In 2021 May the Dark Energy Spectroscopic Instrument (DESI) collaboration began a 5-year spectroscopic redshift survey to produce a detailed map of the evolving three-dimensional structure of the universe between $z=0$ and $z\approx4$. DESI's principle scientific objectives are to place precise constraints on the equation of state of dark energy, the gravitationally driven growth of large-scale structure, and the sum of the neutrino masses, and to explore the observational signatures of primordial inflation. We present DESI Data Release 1 (DR1), which consists of all data acquired during the first 13 months of the DESI main survey, as well as a uniform reprocessing of the DESI Survey Validation data which was previously made public in the DESI Early Data Release. The DR1 main survey includes high-confidence redshifts for 18.7M objects, of which 13.1M are spectroscopically classified as galaxies, 1.6M as quasars, and 4M as stars, making DR1 the largest sample of extragalactic redshifts ever assembled. We summarize the DR1 observations, the spectroscopic data-reduction pipeline and data products, large-scale structure catalogs, value-added catalogs, and describe how to access and interact with the data. In addition to fulfilling its core cosmological objectives with unprecedented precision, we expect DR1 to enable a wide range of transformational astrophysical studies and discoveries.
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Submitted 4 March, 2026; v1 submitted 18 March, 2025;
originally announced March 2025.
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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…
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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.
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Submitted 7 August, 2025; v1 submitted 1 March, 2025;
originally announced March 2025.
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Selecting samples of galaxies with fewer Fingers-of-God
Authors:
Antón Baleato Lizancos,
Uroš Seljak,
Minas Karamanis,
Marco Bonici,
Simone Ferraro
Abstract:
The radial positions of galaxies inferred from their measured redshift appear distorted due to their peculiar velocities. We argue that the contribution from stochastic velocities -- which gives rise to Fingers-of-God (FoG) anisotropy in the inferred maps -- does not lend itself to perturbative modelling already on scales targeted by current experiments. To get around this limitation, we propose t…
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The radial positions of galaxies inferred from their measured redshift appear distorted due to their peculiar velocities. We argue that the contribution from stochastic velocities -- which gives rise to Fingers-of-God (FoG) anisotropy in the inferred maps -- does not lend itself to perturbative modelling already on scales targeted by current experiments. To get around this limitation, we propose to remove FoG using data-driven indicators of their abundance that are local in nature and thus avoid selection biases. In particular, we show that the scale where the measured power spectrum quadrupole changes sign is tightly anti-correlated with both the satellite fraction and the velocity dispersion, and can thus be used to select galaxy samples with fewer FoG. In addition, we show that excluding galaxies in haloes more massive than a given mass threshold can help to discard many of the most problematic galaxies. Such selection could be achieved in practice using maps of the thermal Sunyaev-Zeldovich distortion of the cosmic microwave background frequency spectrum. These techniques could potentially improve reconstructions of the large-scale velocity and displacement fields from the redshift-space positions of galaxies. They may also extend the reach of perturbative models for galaxy clustering, though in practice we find only marginal gains when fitting one-loop EFTofLSS models to simulations with mitigated FoG due to the relevance of other effects entering at two-loop order.
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Submitted 4 July, 2025; v1 submitted 17 January, 2025;
originally announced January 2025.
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Removal of interloper contamination to line-intensity maps using correlations with ancillary tracers of the large-scale structure
Authors:
José Luis Bernal,
Antón Baleato Lizancos
Abstract:
Line-intensity mapping (LIM) offers an approach to obtain three-dimensional maps of the large-scale structure by collecting the aggregate emission from all emitters along the line of sight. The procedure hinges on reconstructing the radial positions of sources by relating the observed frequency to the rest-frame frequency of a target emission line. However, this step is hindered by `interloper-lin…
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Line-intensity mapping (LIM) offers an approach to obtain three-dimensional maps of the large-scale structure by collecting the aggregate emission from all emitters along the line of sight. The procedure hinges on reconstructing the radial positions of sources by relating the observed frequency to the rest-frame frequency of a target emission line. However, this step is hindered by `interloper-line' emission from different cosmological volumes that redshifts into the same observed frequency. In this work, we propose a model-independent technique to remove the contamination of line interlopers using their statistical correlation with external tracers of the large-scale structure, and identify the weights that minimize the variance of the cleaned field. Furthermore, we derive expressions for the resulting power spectra after applying our cleaning procedure, and validate them against simulations. We find that the cleaning performance improves as the correlation between the line interlopers and the external tracer increases, resulting in a gain in the signal-to-noise ratio of up to a factor 6 (2) for the auto- (cross-)power spectrum in idealized scenarios. This approach has the advantage of being model-independent, and is highly complementary to other techniques, as it removes large-scale clustering modes instead of individually masking the brightest sources of contamination.
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Submitted 12 September, 2025; v1 submitted 18 June, 2024;
originally announced June 2024.
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The Simons Observatory: Combining delensing and foreground cleaning for improved constraints on inflation
Authors:
Emilie Hertig,
Kevin Wolz,
Toshiya Namikawa,
Antón Baleato Lizancos,
Susanna Azzoni,
Anthony Challinor
Abstract:
The Simons Observatory (SO), a next-generation ground-based CMB experiment in its final stages of construction, will target primordial $B$-modes with unprecedented sensitivity to set tight bounds on the amplitude of inflationary gravitational waves. Aiming to infer the tensor-to-scalar ratio $r$ with precision $σ(r=0) \leq 0.003$, SO will rely on powerful component-separation algorithms to disting…
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The Simons Observatory (SO), a next-generation ground-based CMB experiment in its final stages of construction, will target primordial $B$-modes with unprecedented sensitivity to set tight bounds on the amplitude of inflationary gravitational waves. Aiming to infer the tensor-to-scalar ratio $r$ with precision $σ(r=0) \leq 0.003$, SO will rely on powerful component-separation algorithms to distinguish the faint primordial signal from stronger sources of large-scale $B$-modes such as Galactic foregrounds and weak gravitational lensing. We present an analysis pipeline that performs delensing and foreground cleaning simultaneously by including multifrequency CMB data and a lensing $B$-mode template in a power-spectrum-based likelihood. Here, we demonstrate this algorithm on masked SO-like simulations containing inhomogeneous noise and non-Gaussian foregrounds. The lensing convergence is reconstructed from high-resolution simulations of the CMB and external mass tracers. Using optimized pixel weights for power spectrum estimation, the target precision for SO's nominal design is achieved and delensing reduces $σ(r)$ by 27-37%, depending on foreground complexity.
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Submitted 21 May, 2024;
originally announced May 2024.
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The Simons Observatory: Combining cross-spectral foreground cleaning with multitracer $B$-mode delensing for improved constraints on inflation
Authors:
Emilie Hertig,
Kevin Wolz,
Toshiya Namikawa,
Antón Baleato Lizancos,
Susanna Azzoni,
Irene Abril-Cabezas,
David Alonso,
Carlo Baccigalupi,
Erminia Calabrese,
Anthony Challinor,
Josquin Errard,
Giulio Fabbian,
Carlos Hervías-Caimapo,
Baptiste Jost,
Nicoletta Krachmalnicoff,
Anto I. Lonappan,
Magdy Morshed,
Luca Pagano,
Blake Sherwin
Abstract:
The Simons Observatory (SO), due to start full science operations in early 2025, aims to set tight constraints on inflationary physics by inferring the tensor-to-scalar ratio $r$ from measurements of CMB polarization $B$-modes. Its nominal design targets a precision $σ(r=0) \leq 0.003$ without delensing. Achieving this goal and further reducing uncertainties requires the mitigation of other source…
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The Simons Observatory (SO), due to start full science operations in early 2025, aims to set tight constraints on inflationary physics by inferring the tensor-to-scalar ratio $r$ from measurements of CMB polarization $B$-modes. Its nominal design targets a precision $σ(r=0) \leq 0.003$ without delensing. Achieving this goal and further reducing uncertainties requires the mitigation of other sources of large-scale $B$-modes such as Galactic foregrounds and weak gravitational lensing. We present an analysis pipeline aiming to estimate $r$ by including delensing within a cross-spectral likelihood, and demonstrate it on SO-like simulations. Lensing $B$-modes are synthesised using internal CMB lensing reconstructions as well as Planck-like CIB maps and LSST-like galaxy density maps. This $B$-mode template is then introduced into SO's power-spectrum-based foreground-cleaning algorithm by extending the likelihood function to include all auto- and cross-spectra between the lensing template and the SAT $B$-modes. Within this framework, we demonstrate the equivalence of map-based and cross-spectral delensing and use it to motivate an optimized pixel-weighting scheme for power spectrum estimation. We start by validating our pipeline in the simplistic case of uniform foreground spectral energy distributions (SEDs). In the absence of primordial $B$-modes, $σ(r)$ decreases by 37% as a result of delensing. Tensor modes at the level of $r=0.01$ are successfully detected by our pipeline. Even with more realistic foreground models including spatial variations in the dust and synchrotron spectral properties, we obtain unbiased estimates of $r$ by employing the moment-expansion method. In this case, delensing-related improvements range between 27% and 31%. These results constitute the first realistic assessment of the delensing performance at SO's nominal sensitivity level. (Abridged)
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Submitted 10 September, 2024; v1 submitted 2 May, 2024;
originally announced May 2024.
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Harmonic analysis of discrete tracers of large-scale structure
Authors:
Antón Baleato Lizancos,
Martin White
Abstract:
It is commonplace in cosmology to analyze fields projected onto the celestial sphere, and in particular density fields that are defined by a set of points e.g. galaxies. When performing an harmonic-space analysis of such data (e.g. an angular power spectrum) using a pixelized map one has to deal with aliasing of small-scale power and pixel window functions. We compare and contrast the approaches t…
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It is commonplace in cosmology to analyze fields projected onto the celestial sphere, and in particular density fields that are defined by a set of points e.g. galaxies. When performing an harmonic-space analysis of such data (e.g. an angular power spectrum) using a pixelized map one has to deal with aliasing of small-scale power and pixel window functions. We compare and contrast the approaches to this problem taken in the cosmic microwave background and large-scale structure communities, and advocate for a direct approach that avoids pixelization. We describe a method for performing a pseudo-spectrum analysis of a galaxy data set and show that it can be implemented efficiently using well-known algorithms for special functions that are suited to acceleration by graphics processing units (GPUs). The method returns the same spectra as the more traditional map-based approach if in the latter the number of pixels is taken to be sufficiently large and the mask is well sampled. The method is readily generalizable to cross-spectra and higher-order functions. It also provides a convenient route for distributing the information in a galaxy catalog directly in harmonic space, as a complement to releasing the configuration-space positions and weights. We make public a code enabling the application of our method to existing and upcoming datasets.
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Submitted 1 April, 2024; v1 submitted 19 December, 2023;
originally announced December 2023.
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The Impact of Anisotropic Redshift Distributions on Angular Clustering
Authors:
Antón Baleato Lizancos,
Martin White
Abstract:
A leading way to constrain physical theories from cosmological observations is to test their predictions for the angular clustering statistics of matter tracers, a technique that is set to become ever more central with the next generation of large imaging surveys. Interpretation of this clustering requires knowledge of the projection kernel, or the redshift distribution of the sources, and the typ…
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A leading way to constrain physical theories from cosmological observations is to test their predictions for the angular clustering statistics of matter tracers, a technique that is set to become ever more central with the next generation of large imaging surveys. Interpretation of this clustering requires knowledge of the projection kernel, or the redshift distribution of the sources, and the typical assumption is an isotropic redshift distribution for the objects. However, variations in the kernel are expected across the survey footprint due to photometric variations and residual observational systematic effects. We develop the formalism for anisotropic projection and present several limiting cases that elucidate the key aspects. We quantify the impact of anisotropies in the redshift distribution on a general class of angular two-point statistics. In particular, we identify a mode-coupling effect that can add power to auto-correlations, including galaxy clustering and cosmic shear, and remove it from certain cross-correlations. If the projection anisotropy is primarily at large scales, the mode-coupling depends upon its variance as a function of redshift; furthermore, it is often of similar shape to the signal. In contrast, the cross-correlation of a field whose selection function is anisotropic with another one featuring no such variations -- such as CMB lensing -- is immune to these effects. We discuss explicitly several special cases of the general formalism including galaxy clustering, galaxy-galaxy lensing, cosmic shear and cross-correlations with CMB lensing, and publicly release a code to compute the biases.
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Submitted 14 July, 2023; v1 submitted 24 May, 2023;
originally announced May 2023.
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The Simons Observatory: pipeline comparison and validation for large-scale B-modes
Authors:
K. Wolz,
S. Azzoni,
C. Hervias-Caimapo,
J. Errard,
N. Krachmalnicoff,
D. Alonso,
C. Baccigalupi,
A. Baleato Lizancos,
M. L. Brown,
E. Calabrese,
J. Chluba,
J. Dunkley,
G. Fabbian,
N. Galitzki,
B. Jost,
M. Morshed,
F. Nati
Abstract:
The upcoming Simons Observatory Small Aperture Telescopes aim at achieving a constraint on the primordial tensor-to-scalar ratio $r$ at the level of $σ(r=0)\lesssim0.003$, observing the polarized CMB in the presence of partial sky coverage, cosmic variance, inhomogeneous non-white noise, and Galactic foregrounds. We present three different analysis pipelines able to constrain $r$ given the latest…
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The upcoming Simons Observatory Small Aperture Telescopes aim at achieving a constraint on the primordial tensor-to-scalar ratio $r$ at the level of $σ(r=0)\lesssim0.003$, observing the polarized CMB in the presence of partial sky coverage, cosmic variance, inhomogeneous non-white noise, and Galactic foregrounds. We present three different analysis pipelines able to constrain $r$ given the latest available instrument performance, and compare their predictions on a set of sky simulations that allow us to explore a number of Galactic foreground models and elements of instrumental noise, relevant for the Simons Observatory. The three pipelines employ different combinations of parametric and non-parametric component separation at the map and power spectrum levels, and use B-mode purification to estimate the CMB B-mode power spectrum. We applied them to a common set of simulated realistic frequency maps, and compared and validated them with focus on their ability to extract robust constraints on the tensor-to-scalar ratio $r$. We evaluated their performance in terms of bias and statistical uncertainty on this parameter. In most of the scenarios the three methodologies achieve similar performance. Nevertheless, several simulations with complex foreground signals lead to a $>2σ$ bias on $r$ if analyzed with the default versions of these pipelines, highlighting the need for more sophisticated pipeline components that marginalize over foreground residuals. We show two such extensions, using power-spectrum-based and map-based methods, that are able to fully reduce the bias on $r$ below the statistical uncertainties in all foreground models explored, at a moderate cost in terms of $σ(r)$.
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Submitted 9 July, 2024; v1 submitted 8 February, 2023;
originally announced February 2023.
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Model independent variance cancellation in CMB lensing cross-correlations
Authors:
Antón Baleato Lizancos,
Simone Ferraro
Abstract:
Cross-correlations of CMB lensing reconstructions with other tracers of matter constrain primordial non-Gaussianity, neutrino masses and structure growth as a function of cosmic time. We formalize a method to improve the precision of these measurements by using a third tracer to remove structure from the lensing reconstructions. Crucially, our method enjoys the variance reduction benefits of a joi…
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Cross-correlations of CMB lensing reconstructions with other tracers of matter constrain primordial non-Gaussianity, neutrino masses and structure growth as a function of cosmic time. We formalize a method to improve the precision of these measurements by using a third tracer to remove structure from the lensing reconstructions. Crucially, our method enjoys the variance reduction benefits of a joint-modelling approach without the need to model the cosmological dependence of the ancillary tracer. We present a first demonstration of variance cancellation using data from Planck and the DESI Legacy Surveys, showing a 10-20% reduction in both lensing power and cross-correlation variance using the Cosmic Infrared Background (CIB) or DESI Legacy Survey Luminous Red Galaxies (LRGs) as matter tracers.
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Submitted 11 July, 2023; v1 submitted 24 January, 2023;
originally announced January 2023.
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The impact of extragalactic foregrounds on internal delensing of CMB B-mode polarization
Authors:
Antón Baleato Lizancos,
Simone Ferraro
Abstract:
The search for primordial $B$-mode polarization of the CMB is limited by the sample variance of $B$-modes produced at later times by gravitational lensing. Constraints can be improved by `delensing': using some proxy of the matter distribution to partially remove the lensing-induced $B$-modes. Current and soon-upcoming experiments will infer a matter map -- at least in part -- from the temperature…
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The search for primordial $B$-mode polarization of the CMB is limited by the sample variance of $B$-modes produced at later times by gravitational lensing. Constraints can be improved by `delensing': using some proxy of the matter distribution to partially remove the lensing-induced $B$-modes. Current and soon-upcoming experiments will infer a matter map -- at least in part -- from the temperature anisotropies of the CMB. These reconstructions are contaminated by extragalactic foregrounds: radio-emitting galaxies, the cosmic infrared background, or the Sunyaev--Zel'dovich effects. Using the Websky simulations, we show that the foregrounds add spurious power to the angular auto-spectrum of delensed $B$-modes via non-Gaussian higher-point functions, biasing constraints on the tensor-to-scalar ratio, $r$. We consider an idealized experiment similar to the Simons Observatory, with no Galactic or atmospheric foregrounds. After removing point sources detectable at 143 GHz and reconstructing lensing from CMB temperature modes $l<3500$ using a Hu-Okamoto quadratic estimator (QE), we infer a value of $r$ that is $1.5\,σ$ higher than the true $r=0$. Reconstructing instead from a minimum-variance ILC map only exacerbates the problem, bringing the bias above $3\,σ$. When the $TT$ estimator is co-added with other QEs or with external matter tracers, new couplings ensue which partially cancel the diluted bias from $TT$. We provide a simple and effective prescription to model these effects. In addition, we demonstrate that the point-source-hardened or shear-only QEs can not only mitigate the biases to acceptable levels, but also lead to lower power than the Hu-Okamoto QE after delensing. Thus, temperature-based reconstructions remain powerful tools in the quest to measure $r$.
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Submitted 22 January, 2023; v1 submitted 18 May, 2022;
originally announced May 2022.
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The Simons Observatory: Constraining inflationary gravitational waves with multi-tracer B-mode delensing
Authors:
Toshiya Namikawa,
Anton Baleato Lizancos,
Naomi Robertson,
Blake D. Sherwin,
Anthony Challinor,
David Alonso,
Susanna Azzoni,
Carlo Baccigalupi,
Erminia Calabrese,
Julien Carron,
Yuji Chinone,
Jens Chluba,
Gabriele Coppi,
Josquin Errard,
Giulio Fabbian,
Simone Ferraro,
Alba Kalaja,
Antony Lewis,
Mathew S. Madhavacheril,
P. Daniel Meerburg,
Joel Meyers,
Federico Nati,
Giorgio Orlando,
Davide Poletti,
Giuseppe Puglisi
, et al. (10 additional authors not shown)
Abstract:
We introduce and validate a delensing framework for the Simons Observatory (SO), which will be used to improve constraints on inflationary gravitational waves (IGWs) by reducing the lensing noise in measurements of the $B$-modes in CMB polarization. SO will initially observe CMB by using three small aperture telescopes and one large-aperture telescope. While polarization maps from small-aperture t…
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We introduce and validate a delensing framework for the Simons Observatory (SO), which will be used to improve constraints on inflationary gravitational waves (IGWs) by reducing the lensing noise in measurements of the $B$-modes in CMB polarization. SO will initially observe CMB by using three small aperture telescopes and one large-aperture telescope. While polarization maps from small-aperture telescopes will be used to constrain IGWs, the internal CMB lensing maps used to delens will be reconstructed from data from the large-aperture telescope. Since lensing maps obtained from the SO data will be noise-dominated on sub-degree scales, the SO lensing framework constructs a template for lensing-induced $B$-modes by combining internal CMB lensing maps with maps of the cosmic infrared background from Planck as well as galaxy density maps from the LSST survey. We construct a likelihood for constraining the tensor-to-scalar ratio $r$ that contains auto- and cross-spectra between observed $B$-modes and the lensing $B$-mode template. We test our delensing analysis pipeline on map-based simulations containing survey non-idealities, but that, for this initial exploration, does not include contamination from Galactic and extragalactic foregrounds. We find that the SO survey masking and inhomogeneous and atmospheric noise have very little impact on the delensing performance, and the $r$ constraint becomes $σ(r)\approx 0.0015$ which is close to that obtained from the idealized forecasts in the absence of the Galactic foreground and is nearly a factor of two tighter than without delensing. We also find that uncertainties in the external large-scale structure tracers used in our multi-tracer delensing pipeline lead to bias much smaller than the $1\,σ$ statistical uncertainties.
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Submitted 15 June, 2022; v1 submitted 19 October, 2021;
originally announced October 2021.
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Delensing the CMB with the cosmic infrared background: the impact of foregrounds
Authors:
Antón Baleato Lizancos,
Anthony Challinor,
Blake D. Sherwin,
Toshiya Namikawa
Abstract:
The most promising avenue for detecting primordial gravitational waves from cosmic inflation is through measurements of degree-scale CMB $B$-mode polarisation. This approach must face the challenge posed by gravitational lensing of the CMB, which obscures the signal of interest. Fortunately, the lensing effects can be partially removed by combining high-resolution $E$-mode measurements with an est…
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The most promising avenue for detecting primordial gravitational waves from cosmic inflation is through measurements of degree-scale CMB $B$-mode polarisation. This approach must face the challenge posed by gravitational lensing of the CMB, which obscures the signal of interest. Fortunately, the lensing effects can be partially removed by combining high-resolution $E$-mode measurements with an estimate of the projected matter distribution. For near-future experiments, the best estimate of the latter will arise from co-adding internal reconstructions (derived from the CMB itself) with external tracers such as the cosmic infrared background (CIB). In this work, we characterise how foregrounds impact the delensing procedure when CIB intensity, $I$, is used as the matter tracer. We find that higher-point functions of the CIB and Galactic dust such as $\langle BEI \rangle_{c}$ and $\langle EIEI \rangle_{c}$ can, in principle, bias the power spectrum of delensed $B$-modes. To quantify these, we first estimate the dust residuals in currently-available CIB maps and upcoming, foreground-cleaned Simons Observatory CMB data. Then, using non-Gaussian simulations of Galactic dust -- extrapolated to the relevant frequencies, assuming the spectral index of polarised dust emission to be fixed at the value determined by Planck -- we show that the bias to any primordial signal is small compared to statistical errors for ground-based experiments, but might be significant for space-based experiments probing very large angular scales. However, mitigation techniques based on multi-frequency cleaning appear to be very effective. We also show, by means of an analytic model, that the bias arising from the higher-point functions of the CIB itself ought to be negligible.
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Submitted 16 June, 2022; v1 submitted 1 February, 2021;
originally announced February 2021.
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Limitations of CMB B-mode template delensing
Authors:
Antón Baleato Lizancos,
Anthony Challinor,
Julien Carron
Abstract:
Efforts to detect a primordial $B$-mode of CMB polarization generated by inflationary gravitational waves ought to mitigate the large variance associated with the $B$-modes produced by gravitational lensing, a process known as delensing. A popular approach to delensing entails building a lensing $B$-mode template by mimicking the lensing operation, either at gradient order or non-perturbatively, u…
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Efforts to detect a primordial $B$-mode of CMB polarization generated by inflationary gravitational waves ought to mitigate the large variance associated with the $B$-modes produced by gravitational lensing, a process known as delensing. A popular approach to delensing entails building a lensing $B$-mode template by mimicking the lensing operation, either at gradient order or non-perturbatively, using high-resolution $E$-mode observations and some proxy of the lensing potential. By explicitly calculating all contributions to two-loop order in lensing to the power spectrum of $B$-modes delensed with such a template in the noise-free limit, we are able to show that: (i) corrections to the leading-order calculation of the lensing $B$-mode power spectrum only enter at the $O(1)\,\%$ level because of extensive cancellations between large terms at next-to-leading order; (ii) these cancellations would disappear if a gradient-order template were to be built from unlensed or delensed $E$-modes, giving rise to a residual delensing floor of $O(10)\,\%$ of the original power; (iii) new cancellations arise when the lensed $E$-modes are used in the gradient-order template, allowing for the delensing floor to be as low as $O(1)\,\%$ of the original power in practical applications of this method; and (iv) these new cancellations would disappear for a non-perturbative template constructed from the lensed $E$-modes, reintroducing a residual delensing floor of $O(10)\,\%$. We further show that the gradient-order template outperforms the non-perturbative one in realistic scenarios with noisy estimates of the $E$-mode polarization and lensing potential. We therefore recommend that in practical applications of $B$-mode template delensing, where the template is constructed directly from the (filtered) observed $E$-modes, the gradient-order approach should be used rather than a non-perturbative remapping.
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Submitted 8 January, 2021; v1 submitted 27 October, 2020;
originally announced October 2020.
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Impact of internal-delensing biases on searches for primordial B-modes of CMB polarisation
Authors:
Antón Baleato Lizancos,
Anthony Challinor,
Julien Carron
Abstract:
Searches for the imprint of primordial gravitational waves in degree-scale CMB $B$-mode polarisation data must account for significant contamination from gravitational lensing. Fortunately, the lensing effects can be partially removed by combining high-resolution $E$-mode measurements with an estimate of the projected matter distribution. In the near future, experimental characteristics will be su…
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Searches for the imprint of primordial gravitational waves in degree-scale CMB $B$-mode polarisation data must account for significant contamination from gravitational lensing. Fortunately, the lensing effects can be partially removed by combining high-resolution $E$-mode measurements with an estimate of the projected matter distribution. In the near future, experimental characteristics will be such that the latter can be reconstructed internally with high fidelity from the observed CMB, with the $EB$ quadratic estimator providing a large fraction of the signal-to-noise. It is a well-known phenomenon in this context that any overlap in modes between the $B$-field to be delensed and the $B$-field from which the reconstruction is derived leads to a suppression of delensed power going beyond that which can be attributed to a mitigation of the lensing effects. More importantly, the variance associated with this spectrum is also reduced, posing the question of whether the additional power suppression could help better constrain the tensor-to-scalar ratio, $r$. In this paper, we show this is not the case, as suggested but not quantified in previous work. We develop an analytic model for the biased delensed $B$-mode angular power spectrum, which suggests a simple renormalisation prescription to avoid bias on the inferred tensor-to-scalar ratio. With this approach, we learn that the bias necessarily leads to a degradation of the signal-to-noise on a primordial component compared to "unbiased delensing". Next, we assess the impact of removing from the lensing reconstruction any overlapping $B$-modes on our ability to constrain $r$, showing that it is in general advantageous to do this rather than modeling or renormalising the bias. Finally, we verify these results within a maximum-likelihood inference framework applied to simulations.
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Submitted 11 March, 2021; v1 submitted 3 July, 2020;
originally announced July 2020.
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The Simons Observatory: Astro2020 Decadal Project Whitepaper
Authors:
The Simons Observatory Collaboration,
Maximilian H. Abitbol,
Shunsuke Adachi,
Peter Ade,
James Aguirre,
Zeeshan Ahmed,
Simone Aiola,
Aamir Ali,
David Alonso,
Marcelo A. Alvarez,
Kam Arnold,
Peter Ashton,
Zachary Atkins,
Jason Austermann,
Humna Awan,
Carlo Baccigalupi,
Taylor Baildon,
Anton Baleato Lizancos,
Darcy Barron,
Nick Battaglia,
Richard Battye,
Eric Baxter,
Andrew Bazarko,
James A. Beall,
Rachel Bean
, et al. (258 additional authors not shown)
Abstract:
The Simons Observatory (SO) is a ground-based cosmic microwave background (CMB) experiment sited on Cerro Toco in the Atacama Desert in Chile that promises to provide breakthrough discoveries in fundamental physics, cosmology, and astrophysics. Supported by the Simons Foundation, the Heising-Simons Foundation, and with contributions from collaborating institutions, SO will see first light in 2021…
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The Simons Observatory (SO) is a ground-based cosmic microwave background (CMB) experiment sited on Cerro Toco in the Atacama Desert in Chile that promises to provide breakthrough discoveries in fundamental physics, cosmology, and astrophysics. Supported by the Simons Foundation, the Heising-Simons Foundation, and with contributions from collaborating institutions, SO will see first light in 2021 and start a five year survey in 2022. SO has 287 collaborators from 12 countries and 53 institutions, including 85 students and 90 postdocs.
The SO experiment in its currently funded form ('SO-Nominal') consists of three 0.4 m Small Aperture Telescopes (SATs) and one 6 m Large Aperture Telescope (LAT). Optimized for minimizing systematic errors in polarization measurements at large angular scales, the SATs will perform a deep, degree-scale survey of 10% of the sky to search for the signature of primordial gravitational waves. The LAT will survey 40% of the sky with arc-minute resolution. These observations will measure (or limit) the sum of neutrino masses, search for light relics, measure the early behavior of Dark Energy, and refine our understanding of the intergalactic medium, clusters and the role of feedback in galaxy formation.
With up to ten times the sensitivity and five times the angular resolution of the Planck satellite, and roughly an order of magnitude increase in mapping speed over currently operating ("Stage 3") experiments, SO will measure the CMB temperature and polarization fluctuations to exquisite precision in six frequency bands from 27 to 280 GHz. SO will rapidly advance CMB science while informing the design of future observatories such as CMB-S4.
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Submitted 16 July, 2019;
originally announced July 2019.