Showing 1–50 of 86 results for author: Scott, T

An optimal control approach for neural network architecture adaptation with a posteriori error estimation

Authors: C G Krishnanunni, Thomas Scott, Tan Bui-Thanh

Abstract: This work presents a novel approach for adapting neural network architecture along the depth based on a posteriori error estimation. By formulating neural network training as a continuous-time optimal control problem, we derive rigorous error estimates that quantify how approximation error distributes across network layers. This error decomposition enables a principled depth adaptation strategy: n… ▽ More This work presents a novel approach for adapting neural network architecture along the depth based on a posteriori error estimation. By formulating neural network training as a continuous-time optimal control problem, we derive rigorous error estimates that quantify how approximation error distributes across network layers. This error decomposition enables a principled depth adaptation strategy: new layers are inserted at locations of maximum estimated error, allowing the network to efficiently capture complex, nonlinear variations in the underlying problem. Our framework introduces a novel network architecture that treats weights and biases as piecewise linear functions varying across layers, with the error estimator bounding the discrepancy between this discrete representation and the true continuous optimal control solution. The approach leverages dual weighted residual methodology from finite element analysis to derive computable upper bounds on the functional error. A key theoretical contribution is the derivation of explicit error bounds that decompose the total approximation error into interval-wise contributions, providing a rigorous basis for targeted architecture refinement. We demonstrate the effectiveness of our method on scientific datasets, including learning the observable-to-parameter map for the Navier-Stokes equation. Numerical results reveal that our approach consistently outperforms existing architecture adaptation methods in terms of generalization performance. △ Less

Submitted 8 July, 2026; originally announced July 2026.

Building AI-Ready Data Systems for Space Life Sciences, Aerospace Medicine, and Deep Space Exploration

Authors: Sylvain V. Costes, Sergio Garcia Busto, Ryan T. Scott, James A. Casaletto, Gautier Bardi de Fourtou, Brian M. Evarts, Amanda M. Saravia-Butler, Xavier-Lewis Palmer, Rodrigo Coutinho de Almeida, Laetitia Frost, Jelena Tešić, Afshin Beheshti, Christopher E. Mason, Peter W. Rose, Sergio E. Baranzini, Lauren M. Sanders, Stefania Giacomello, Pedro Madrigal

Abstract: While AI holds the potential to revolutionize space life sciences, realizing this promise is contingent upon the systematic restructuring of heterogeneous spaceflight biological data into machine-actionable, AI-ready forms. Even though open access principles support human reuse and scientific reproducibility, this does not necessarily enable AI systems to access and analyze such a diverse set of s… ▽ More While AI holds the potential to revolutionize space life sciences, realizing this promise is contingent upon the systematic restructuring of heterogeneous spaceflight biological data into machine-actionable, AI-ready forms. Even though open access principles support human reuse and scientific reproducibility, this does not necessarily enable AI systems to access and analyze such a diverse set of scientific datasets. In addition, the growing array of AI approaches places distinct demands on data structure, metadata, and access interfaces. In order to respond to such growing changes we propose a three-tier approach, proceeding from FAIR to AI-ready to space-ready data. We discuss existing infrastructures and how they can be improved to close the AI access gap. We conclude by proposing a neutral international coordinating body as the governance backbone for the trustworthy, agent-accessible space biology infrastructure that deep space biological research will require. △ Less

Submitted 27 June, 2026; originally announced June 2026.

Comments: 26 pages, 3 figures, 1 table, 1 supplementary table

MSC Class: 92C99 (Primary) 68T01 (Secondary) ACM Class: J.3

Diagrammatic Monte Carlo for positron-molecule many-body theory

Authors: T. A. Scott, S. K. Gregg, D. G. Green

Abstract: A diagrammatic Monte Carlo evaluation of the ladder series contributions to the correlation potential (self energy) of a positron in the field of a molecule is presented. The $GW$@TDHF, virtual-positronium ($T$-matrix), and positron-hole Goldstone ladder series contributions are stochastically sampled order-by-order within the Tamm-Dancoff approximation, which is exact for the latter two classes,… ▽ More A diagrammatic Monte Carlo evaluation of the ladder series contributions to the correlation potential (self energy) of a positron in the field of a molecule is presented. The $GW$@TDHF, virtual-positronium ($T$-matrix), and positron-hole Goldstone ladder series contributions are stochastically sampled order-by-order within the Tamm-Dancoff approximation, which is exact for the latter two classes, with Ces{á}ro-Riesz resummation used to extrapolate to infinite order. Gaussian bases are employed and Coulomb matrix elements are represented via density fitting, with the three centre integrals the largest arrays required to be stored in memory. The stochastic approach thus realizes a reduction in memory of the largest arrays required on the order of the number of molecular orbitals in the basis $N\sim$10$^2$--10$^3$ compared to the exact deterministic solution of Bethe-Salpeter equations [J. Hofierka, B. Cunningham, C. M. Rawlins, C. H. Patterson and D. G. Green, Nature {\bf 606}, {688} (2022)]. Benchmark results for lithium hydride show quantitative agreement with exact diagonalisation, notably demonstrating the successful stochastic summation of the virtual-positronium infinite electron-positron ladder series. △ Less

Submitted 21 July, 2026; v1 submitted 1 June, 2026; originally announced June 2026.

Comments: This version: some miscompiled references and other typos fixed

Lithium enrichment threatens to curb fusion deployment

Authors: Samuel H. Ward, Richard J. Pearson, Thomas B. Scott, Niek J. Lopes Cardozo

Abstract: The impact of lithium isotopic enrichment on the global deployment of nuclear fusion energy is analysed. Lithium - the 6Li isotope in particular - is essentially one of two elemental fuels required by fusion reactors for tritium breeding. Whilst variable consumption of lithium is low enough to present negligible cost, it is instead the large stored inventory volume (50-100 tonnes) and its required… ▽ More The impact of lithium isotopic enrichment on the global deployment of nuclear fusion energy is analysed. Lithium - the 6Li isotope in particular - is essentially one of two elemental fuels required by fusion reactors for tritium breeding. Whilst variable consumption of lithium is low enough to present negligible cost, it is instead the large stored inventory volume (50-100 tonnes) and its required enrichment that compound to significantly drive capital costs. These costs are driven by the inefficiency of the tritium breeding process, making this challenge fundamental to almost all fusion power plant concepts. Financing would further compound these effects, making lithium fusion fuels more akin to an upfront capital expenditure than operational expenditure. Other potential barriers to fusion deployment created by lithium are also discussed: enrichment technologies of today are shown to be too expensive, not scalable, and environmentally risky, and highly enriched 6Li is a controlled substance. Mitigating actions include: developing alternative enrichment technologies that are affordable, scalable, and do not rely on mercury; incorporating lithium enrichment as an explicit cost driver in reactor design processes, producing more compact reactors with smaller lithium inventories; establishing distinct enrichment levels to enable supply chain monitoring for misuse; and the most radical solution: breeding blankets that use natural, unenriched lithium. These actions may impact tritium breeding capabilities, which calls for an urgent re-assessment of the tritium breeding paradigm. Whatever solution is sought, lithium supply is a mission-critical issue that needs urgently addressing. △ Less

Submitted 6 May, 2026; originally announced May 2026.

Rendezvous Planning from Sparse Observations of Optimally Controlled Targets

Authors: Thomas A. Scott, Lukas Taus, Yen-Hsi Richard Tsai, Tan Bui-Thanh, Justin G. R. Delva

Abstract: We develop a probabilistic framework for \emph{rendezvous planning}: given sparse, noisy observations of a fast-moving target, plan rendezvous spatiotemporal coordinates for a set of significantly slower seeking agents. The unknown target trajectory is estimated under uncertain dynamics using a filtering approach that combines a kernel-based maximum a posteriori estimation with Gaussian process co… ▽ More We develop a probabilistic framework for \emph{rendezvous planning}: given sparse, noisy observations of a fast-moving target, plan rendezvous spatiotemporal coordinates for a set of significantly slower seeking agents. The unknown target trajectory is estimated under uncertain dynamics using a filtering approach that combines a kernel-based maximum a posteriori estimation with Gaussian process correction, producing a mixture over trajectory hypotheses. This estimate is used to select spatiotemporal rendezvous points that maximize the probability of successful rendezvous. Points are chosen sequentially by greedily minimizing failure probability in the current belief space, which is updated after each step by conditioning on unsuccessful rendezvous attempts. We show that the failure-conditioned update correctly captures the posterior belief for subsequent decisions, ensuring that each step in the greedy sequence is informed by a statistically consistent representation of the remaining search space, and derive the corresponding Bayesian updates incorporating temporal correlations intrinsic to the trajectory model. This result provides a systematic framework for planning under uncertainty in applications of autonomous rendezvous such as unmanned aerial vehicle refueling, spacecraft servicing, autonomous surface vessel operations, search and rescue missions, and missile defense. In each, the motion of the target entity can be modeled using a system of differential equations undergoing optimal control for a chosen objective, in our example case Hamilton--Jacobi--Bellman solutions for minimum arrival time of a Dubins car with uncertain turning radius and destination. △ Less

Submitted 1 April, 2026; originally announced April 2026.

The Python Simulations of Chemistry Framework: 10 years of an open-source quantum chemistry project

Authors: Qiming Sun, Matthew R Hermes, Xiaojie Wu, Huanchen Zhai, Xing Zhang, Abdelrahman M. Ahmed, Juan José Aucar, Oliver J. Backhouse, Samragni Banerjee, Peng Bao, Nikolay A. Bogdanov, Kyle Bystrom, Frédéric Chapoton, Ning-Yuan Chen, Ivan Yu. Chernyshov, Helen S. Clifford, Sander Cohen-Janes, Zhi-Hao Cui, Yann D. Damour, Nike Dattani, Linus Bjarne Dittmer, Sebastian Ehlert, Janus Juul Eriksen, Francesco A. Evangelista, Simon A. Ewing , et al. (78 additional authors not shown)

Abstract: Over the past decade, the Python-based Simulations of Chemistry Framework (PySCF) has developed into a widely used open-source platform for electronic structure theory and quantum chemical method development. This article reviews the major advances since the previous overview in 2020, covering new modules and methodology, infrastructure changes, and performance benchmarks. Over the past decade, the Python-based Simulations of Chemistry Framework (PySCF) has developed into a widely used open-source platform for electronic structure theory and quantum chemical method development. This article reviews the major advances since the previous overview in 2020, covering new modules and methodology, infrastructure changes, and performance benchmarks. △ Less

Submitted 7 April, 2026; v1 submitted 14 March, 2026; originally announced March 2026.

Toward Scalable Audio Description Quality Control: A Workflow for Evaluating Human and VLM Raters

Authors: Lana Do, Gio Jung, Juvenal Francisco Barajas, Andrew Taylor Scott, Shasta Ihorn, Alexander Mario Blum, Vassilis Athitsos, Ilmi Yoon

Abstract: Digital video is central to communication, education, and entertainment, but without audio description (AD), blind and low-vision users are excluded. While crowdsourced platforms and vision-language models (VLMs) expand AD production, quality is rarely checked systematically. Existing evaluations rely on NLP metrics and short-clip guidelines, leaving open the question of how to assess long-form AD… ▽ More Digital video is central to communication, education, and entertainment, but without audio description (AD), blind and low-vision users are excluded. While crowdsourced platforms and vision-language models (VLMs) expand AD production, quality is rarely checked systematically. Existing evaluations rely on NLP metrics and short-clip guidelines, leaving open the question of how to assess long-form AD quality at scale. To address this, we developed a methodological workflow using Item Response Theory to evaluate VLM and human rater proficiency against expert-established ground truth. Evaluations were based on a six-dimensional framework, grounded in professional guidelines and shaped by insights from our accessibility experts and blind consultants. Findings suggest that top-performing VLMs can approximate ground-truth ratings at levels comparable to human raters. However, qualitative analysis reveals that VLM reasoning is less reliable and actionable than that of human respondents. These insights underscore the potential of hybrid evaluation systems that leverage VLMs alongside human oversight, offering a path toward scalable AD quality control. △ Less

Submitted 6 May, 2026; v1 submitted 1 February, 2026; originally announced February 2026.

Exploring the effects of diffuse ionised gas in two local analogues of high-redshift star-forming galaxies

Authors: P. Lagos, A. Nigoche-Netro, T. C. Scott, C. Sengupta, R. Demarco

Abstract: Aims. We investigate the impact of diffuse ionised gas (DIG) on the determination of emission line ratios and gas-phase metallicities in two local analogues of high-redshift star-forming galaxies: UM 462 and IIZw 40. Understanding how DIG affects these quantities is essential for interpreting unresolved observations of distant galaxies, where integrated spectra are often used to trace their chemic… ▽ More Aims. We investigate the impact of diffuse ionised gas (DIG) on the determination of emission line ratios and gas-phase metallicities in two local analogues of high-redshift star-forming galaxies: UM 462 and IIZw 40. Understanding how DIG affects these quantities is essential for interpreting unresolved observations of distant galaxies, where integrated spectra are often used to trace their chemical evolution. Methods. Using archival Very Large Telescope, Multi-Unit Spectroscopic Explorer (MUSE) data, we spatially resolved the warm ionised medium of both galaxies. We derived oxygen abundances through the direct method and several HII-based strong-line calibrators, and we used the H$α$ surface brightness ($Σ$(H$α$)) to distinguish regions dominated by HII or DIG emission. Results. Oxygen abundances derived from the N2 and O3N2 indices show an inverse correlation with $Σ$(H$α$), ionisation parameter, and EW(H$α$), with DIG-dominated regions exhibiting higher 12+log(O/H) than the galaxy mean by $\sim$0.2 dex in UM 462 and $\sim$0.1 dex in IIZw 40. The metallicity differences between HII-dominated and DIG-dominated $Σ$(H$α$) bins reach $\sim$0.4 dex and $\sim$0.3 dex in UM 462 and IIZw 40, respectively. The observed trends with $Σ$(H$α$), metallicity, EW(H$α$), and ionisation parameter indicate smoothly varying ionisation conditions rather than true abundance variations. These effects reflect different ionisation sources and levels, and can produce spurious metallicity gradients in galaxies with extended DIG structures, potentially mimicking signatures of metal-poor gas infall. In our sample, DIG ionisation is most likely dominated by photon leakage from H II regions, with additional contributions from feedback-driven shocks. △ Less

Submitted 27 January, 2026; originally announced January 2026.

Comments: Accepted for publication in A&A. The abstract has been modified to comply with the astro-ph length requirement

MeerKAT HI observations of Low Surface Brightness/Ultradiffuse Galaxy Candidates Projected around Two Southern Loose Groups

Authors: Chandreyee Sengupta, Tom C. Scott, Hao Chen, Hyein Yoon, Yogesh Chandola, Mengtian Li, Gyula I. G. Józsa, O. Ivy Wong, Yin-Zhe Ma, Patricio Lagos, Ruta Kale, Denis Tramonte

Abstract: A large catalogue of low surface brightness galaxies (LSBGs) from the Dark Energy Survey showed significant clustering around nearby galaxy groups and clusters. Using the HIPASS survey, we tried to determine the redshift of a sub-sample of these LSBGs and determine whether they were members of the groups they were projected near, but this was hampered by HIPASS's high spectral rms. This letter rep… ▽ More A large catalogue of low surface brightness galaxies (LSBGs) from the Dark Energy Survey showed significant clustering around nearby galaxy groups and clusters. Using the HIPASS survey, we tried to determine the redshift of a sub-sample of these LSBGs and determine whether they were members of the groups they were projected near, but this was hampered by HIPASS's high spectral rms. This letter reports on MeerKAT H I observations to determine the redshifts of 52 LSBG candidates projected in the vicinity of two groups from our previous HIPASS study. The main goal is to investigate and ascertain whether these LSBGs are genuine group members. H I was detected with MeerKAT and redshifts were determined for only five of the 52 candidates within a velocity range of $\pm$ 2500 km/s of their respective group velocities. All five H I detections were blue LSBGs and two of them were confirmed to be ultradiffuse galaxies (UDGs). Both these UDGs were group members, while the other three detections were either foreground or background galaxies. In this letter we explore scenarios that can explain the 90% non-detection. MeerKAT's excellent sensitivity allows us to conclude that the majority of the non-detected candidates, particularly the blue galaxies, are not group members but lie at higher redshifts. However, this still leaves the open question as why Tanoglidis LSBG candidates, in particular the red ones, appear to be clustered in projection around nearby groups. △ Less

Submitted 16 June, 2025; originally announced June 2025.

Comments: Accepted in ApJ Letters

ALMA-JELLY I: High Resolution CO(2-1) Observations of Ongoing Ram Pressure Stripping in NGC 4858 Reveal Asymmetrical Gas Tail Formation and Fallback

Authors: Harrison J. Souchereau, Jeffrey D. P. Kenney, Pavel Jachym, Ming Sun, William J. Cramer, Masafumi Yagi, Alessandro Boselli, Elias Brinks, Francoise Combes, Luca Cortese, Boris Deshev, Matteo Fossati, Romana Grossova, Rongxin Luo, Jan Palous, Tom C. Scott

Abstract: We present new CO(2-1) observations (resolution $\sim1" = 460$pc) of the Coma cluster jellyfish galaxy NGC 4858 obtained from the ALMA-JELLY large program. Analyzing this data alongside complimentary Subaru H$α$ and HST (F600LP / F350LP) observations, we find numerous structural and kinematic features indicative of the effects from strong, inclined ram pressure, including an asymmetric inner gas t… ▽ More We present new CO(2-1) observations (resolution $\sim1" = 460$pc) of the Coma cluster jellyfish galaxy NGC 4858 obtained from the ALMA-JELLY large program. Analyzing this data alongside complimentary Subaru H$α$ and HST (F600LP / F350LP) observations, we find numerous structural and kinematic features indicative of the effects from strong, inclined ram pressure, including an asymmetric inner gas tail. We estimate a highly-inclined disk-wind angle of $φ_{DW} = 75^{+10}_{-27}$. By subtracting a simple circular velocity model, we find (1): gas clumps that are being accelerated by ram pressure, and (2): signatures of gas clumps that had been previously pushed out of the disk but are now falling inwards. We also discuss head-tail morphologies in star complexes within the stellar disk that appear to be RPS-influenced. Lastly, we compare this galaxy to state-of-the-art galaxy ``wind tunnel'' simulations. We find that this galaxy is one of the best nearby examples of strong and inclined ram pressure gas stripping, and of gas that is perturbed by ram pressure but not fully stripped and falls back. We emphasize the importance of torques due to ram pressure in highly-inclined interactions, which help drive gas inwards on the side rotating against the wind, contributing to the formation of asymmetric inner RPS tails. △ Less

Submitted 8 June, 2025; originally announced June 2025.

Probability Bracket Notation for Probability Modeling

Authors: Xing M. Wang, Tony C. Scott

Abstract: Following the Dirac Notation in Quantum Mechanics (QM), we propose the Bracket Notation (PBN) by defining a probability-bra (P-bra), P-ket, P-bracket, P-identity, etc. Using the PBN, many formulae, such as normalizations and expectations in systems of one or more random variables, can now be written in abstract basis-independent expressions, which are easy to expand by inserting a proper P-identit… ▽ More Following the Dirac Notation in Quantum Mechanics (QM), we propose the Bracket Notation (PBN) by defining a probability-bra (P-bra), P-ket, P-bracket, P-identity, etc. Using the PBN, many formulae, such as normalizations and expectations in systems of one or more random variables, can now be written in abstract basis-independent expressions, which are easy to expand by inserting a proper P-identity. The time evolution of homogeneous Markov processes can also be formatted in such a way. Our system P-kets are identified with probability vectors, and our system P-bra is comparable to the Doi state function or the Peliti standard bra. In the Heisenberg picture of the PBN, a random variable becomes a stochastic process, and the Chapman-Kolmogorov equations are obtained by inserting a time-dependent P-identity. Also, some QM expressions in the Dirac notation are naturally transformed into probability expressions in PBN by a special Wick rotation. Potential applications show the usefulness of the PBN beyond the constrained domain and range of Hermitian operators on Hilbert Spaces in QM all the way to IT. △ Less

Submitted 6 February, 2025; originally announced February 2025.

Comments: 20 pages

Journal ref: Axioms 2024, 13(8), 564

High-resolution HI mapping of nearby extremely metal-poor blue compact dwarf galaxies

Authors: Tom C. Scott, Elias Brinks, Chandreyee Sengupta, Patricio Lagos

Abstract: Optical observations of Blue Compact Dwarf galaxies (BCDs) show they typically have high specific star formation rates and low metallicites. A subset of these galaxies (those with the lowest gas phase metallicities) display cometary optical morphologies similar to those found at high redshift. Whether this combination of properties predominantly arises from interactions with neighbours or accretio… ▽ More Optical observations of Blue Compact Dwarf galaxies (BCDs) show they typically have high specific star formation rates and low metallicites. A subset of these galaxies (those with the lowest gas phase metallicities) display cometary optical morphologies similar to those found at high redshift. Whether this combination of properties predominantly arises from interactions with neighbours or accretion from the cosmic web or something else remains unclear. We used high resolution HI mapping to gain insights into the processes driving the observed properties of a sample of extremely metal poor (XMP) BCDs. We present Very Large Array B- and C-configuration HI mapping of four BCDs. For three of the targeted BCDs we also detect and map the HI in their nearby companions. In these three cases there is HI evidence for a recent flyby interaction between the BCD and a nearby companion. The HI evidence for recent interactions for these three BCDs is corroborated by our analysis of the tidal forces exerted on the BCDs by companions with available spectroscopic redshifts. For J0204-1009 we had sufficient spatial resolution to determine that it is dark matter dominated and estimate its DM halo mass to be in the range 1.2 x 10^11 to 5.2 x 10^11 solar masses. It is the most isolated BCD in our small sample, J0301-0052, which shows one of the most asymmetric HI morphologies. J0301-0052 has a similar cometary HI morphology to the BCD's optical morphology, although the HI column density maximum is projected at the end of the of the optical tail. Our HI observations suggest J0301-0052 may be undergoing a merger, while the other BCDs show evidence of a recent tidal interaction with a near neighbour. While our selection criteria favoured BCDs with companions our results are consistent with the earlier finding by other authors that most BCDs are associated with either mild tidal interactions or mergers. △ Less

Submitted 3 January, 2025; v1 submitted 28 October, 2024; originally announced October 2024.

Comments: 15 pages with 18 Figures

Journal ref: A&A 692, A51 (2024)

Euclid. IV. The NISP Calibration Unit

Authors: Euclid Collaboration, F. Hormuth, K. Jahnke, M. Schirmer, C. G. -Y. Lee, T. Scott, R. Barbier, S. Ferriol, W. Gillard, F. Grupp, R. Holmes, W. Holmes, B. Kubik, J. Macias-Perez, M. Laurent, J. Marpaud, M. Marton, E. Medinaceli, G. Morgante, R. Toledo-Moreo, M. Trifoglio, Hans-Walter Rix, A. Secroun, M. Seiffert, P. Stassi , et al. (310 additional authors not shown)

Abstract: The near-infrared calibration unit (NI-CU) on board Euclid's Near-Infrared Spectrometer and Photometer (NISP) is the first astronomical calibration lamp based on light-emitting diodes (LEDs) to be operated in space. Euclid is a mission in ESA's Cosmic Vision 2015-2025 framework, to explore the dark universe and provide a next-level characterisation of the nature of gravitation, dark matter, and da… ▽ More The near-infrared calibration unit (NI-CU) on board Euclid's Near-Infrared Spectrometer and Photometer (NISP) is the first astronomical calibration lamp based on light-emitting diodes (LEDs) to be operated in space. Euclid is a mission in ESA's Cosmic Vision 2015-2025 framework, to explore the dark universe and provide a next-level characterisation of the nature of gravitation, dark matter, and dark energy. Calibrating photometric and spectrometric measurements of galaxies to better than 1.5% accuracy in a survey homogeneously mapping ~14000 deg^2 of extragalactic sky requires a very detailed characterisation of near-infrared (NIR) detector properties, as well their constant monitoring in flight. To cover two of the main contributions - relative pixel-to-pixel sensitivity and non-linearity characteristics - as well as support other calibration activities, NI-CU was designed to provide spatially approximately homogeneous (<12% variations) and temporally stable illumination (0.1%-0.2% over 1200s) over the NISP detector plane, with minimal power consumption and energy dissipation. NI-CU is covers the spectral range ~[900,1900] nm - at cryo-operating temperature - at 5 fixed independent wavelengths to capture wavelength-dependent behaviour of the detectors, with fluence over a dynamic range of >=100 from ~15 ph s^-1 pixel^-1 to >1500 ph s^-1 pixel^-1. For this functionality, NI-CU is based on LEDs. We describe the rationale behind the decision and design process, describe the challenges in sourcing the right LEDs, as well as the qualification process and lessons learned. We also provide a description of the completed NI-CU, its capabilities and performance as well as its limits. NI-CU has been integrated into NISP and the Euclid satellite, and since Euclid's launch in July 2023 has started supporting survey operations. △ Less

Submitted 10 July, 2024; v1 submitted 22 May, 2024; originally announced May 2024.

Comments: Paper accepted for publication in A&A as part of the special issue 'Euclid on Sky', which contains Euclid key reference papers and first results from the Euclid Early Release Observations

Journal ref: A&A 697, A4 (2025)

Catalogue of nearby blue and near-solar gas metallicity SDSS dwarf galaxies

Authors: Yan Guo, Chandreyee Sengupta, Tom. C. Scott, Patricio Lagos, Yu Luo

Abstract: A less explored aspect of dwarf galaxies is their metallicity evolution. Generally, dwarfs have lower metallicities than Hubble sequence late type galaxies but in reality, dwarfs span a wide range of metallicities with several open questions regarding the formation and evolution of the lowest and the highest metallicity dwarfs. We present a catalogue of 3459 blue, nearby, star forming dwarf galaxi… ▽ More A less explored aspect of dwarf galaxies is their metallicity evolution. Generally, dwarfs have lower metallicities than Hubble sequence late type galaxies but in reality, dwarfs span a wide range of metallicities with several open questions regarding the formation and evolution of the lowest and the highest metallicity dwarfs. We present a catalogue of 3459 blue, nearby, star forming dwarf galaxies extracted from SDSS DR16 including calculation of their metallicities using the mean of several calibrators. To compile our catalogue we applied redshift, absolute magnitude, stellar mass, optical diameter, and line flux signal to noise criteria. This produced a catalogue from the upper end of the dwarf galaxy stellar mass range. Our catalogued dwarfs have blue g - i colours and Hbeta equivalent widths, indicative of having undergone a recent episode of star formation, although their star formation rates (SFR) suggest only a moderate to low enhancement in star formation, similar to the SFRs in low surface brightness and evolved tidal dwarfs. While the catalogued dwarfs cover a range of metallicities, their mean metallicity is about 0.2 dex below solar metallicity, indicating relatively chemically evolved galaxies. The vast majority of the catalogue, with clean photometry, are relatively isolated dwarfs with only modest star formation rates and a narrow range of g - i colour, consistent with internally driven episodic mild bursts of star formation. The presented catalogue's robust metallicity estimates for nearby SDSS dwarf galaxies will help target future studies to understand the physical processes driving the metallicity evolution of dwarfs. △ Less

Submitted 21 February, 2024; originally announced February 2024.

Comments: Accepted in MNRAS

HI in high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9

Authors: Yan Guo, C. Sengupta, T. C. Scott, P. Lagos, Y. Luo

Abstract: We present resolved GMRT HI observations of the high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9 (z = 0.005) (hereafter J2306) and investigate whether it could be a Tidal Dwarf Galaxy (TDG) candidate. TDGs are observed to have higher metallicities than normal dwarfs. J2306 has an unusual combination of a blue g -- r colour of 0.23 mag, irregular optical morphology and high-metalli… ▽ More We present resolved GMRT HI observations of the high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9 (z = 0.005) (hereafter J2306) and investigate whether it could be a Tidal Dwarf Galaxy (TDG) candidate. TDGs are observed to have higher metallicities than normal dwarfs. J2306 has an unusual combination of a blue g -- r colour of 0.23 mag, irregular optical morphology and high-metallicity (12 + log(O/H) = 8.68$\pm$0.14), making it an interesting galaxy to study in more detail. We find J2306 to be an HI rich galaxy with a large extended, unperturbed rotating HI disk. Using our HI data we estimated its dynamical mass and found the galaxy to be dark matter (DM) dominated within its HI radius. The quantity of DM, inferred from its dynamical mass, appears to rule out J2306 as an evolved TDG. A wide area environment search reveals J2306 to be isolated from any larger galaxies which could have been the source of its high gas metallicity. Additionally, the HI morphology and kinematics of the galaxy show no indication of a recent merger to explain the high-metallicity. Further detailed optical spectroscopic observations of J2306 might provide an answer to how a seemingly ordinary irregular dwarf galaxy achieved such a high level of metal enrichment. △ Less

Submitted 28 December, 2023; v1 submitted 27 November, 2023; originally announced November 2023.

Comments: 11 pages, 5 figures, Accepted in RAA

Explainable machine learning identifies multi-omics signatures of muscle response to spaceflight in mice

Authors: Kevin Li, Riya Desai, Ryan T. Scott, Joel Ricky Steele, Meera Machado, Samuel Demharter, Adrienne Hoarfrost, Jessica L. Braun, Val A. Fajardo, Lauren M. Sanders, Sylvain V. Costes

Abstract: The adverse effects of microgravity exposure on mammalian physiology during spaceflight necessitate a deep understanding of the underlying mechanisms to develop effective countermeasures. One such concern is muscle atrophy, which is partly attributed to the dysregulation of calcium levels due to abnormalities in SERCA pump functioning. To identify potential biomarkers for this condition, multi-omi… ▽ More The adverse effects of microgravity exposure on mammalian physiology during spaceflight necessitate a deep understanding of the underlying mechanisms to develop effective countermeasures. One such concern is muscle atrophy, which is partly attributed to the dysregulation of calcium levels due to abnormalities in SERCA pump functioning. To identify potential biomarkers for this condition, multi-omics data and physiological data available on the NASA Open Science Data Repository (osdr.nasa.gov) were used, and machine learning methods were employed. Specifically, we used multi-omics (transcriptomic, proteomic, and DNA methylation) data and calcium reuptake data collected from C57BL/6J mouse soleus and tibialis anterior tissues during several 30+ day-long missions on the international space station. The QLattice symbolic regression algorithm was introduced to generate highly explainable models that predict either experimental conditions or calcium reuptake levels based on multi-omics features. The list of candidate models established by QLattice was used to identify key features contributing to the predictive capability of these models, with Acyp1 and Rps7 proteins found to be the most predictive biomarkers related to the resilience of the tibialis anterior muscle in space. These findings could serve as targets for future interventions aiming to reduce the extent of muscle atrophy during space travel. △ Less

Submitted 27 September, 2023; originally announced September 2023.

Modelling of COVID-19 Using Fractional Differential Equations

Authors: Rishi Patel, P. Sainani, M. Brar, R. Patel, X. Li, J. Drozd, F. A. Chishtie, A. Benterki, T. C. Scott, S. R. Valluri

Abstract: In this work, we have described the mathematical modeling of COVID-19 transmission using fractional differential equations. The mathematical modeling of infectious disease goes back to the 1760s when the famous mathematician Daniel Bernoulli used an elementary version of compartmental modeling to find the effectiveness of deliberate smallpox inoculation on life expectancy. We have used the well-kn… ▽ More In this work, we have described the mathematical modeling of COVID-19 transmission using fractional differential equations. The mathematical modeling of infectious disease goes back to the 1760s when the famous mathematician Daniel Bernoulli used an elementary version of compartmental modeling to find the effectiveness of deliberate smallpox inoculation on life expectancy. We have used the well-known SIR (Susceptible, Infected and Recovered) model of Kermack & McKendrick to extend the analysis further by including exposure, quarantining, insusceptibility and deaths in a SEIQRDP model. Further, we have generalized this model by using the solutions of Fractional Differential Equations to test the accuracy and validity of the mathematical modeling techniques against Canadian COVID-19 trends and spread of real-world disease. Our work also emphasizes the importance of Personal Protection Equipment (PPE) and impact of social distancing on controlling the spread of COVID-19. △ Less

Submitted 30 July, 2023; originally announced July 2023.

Comments: 14 Pages of Text, 24 Figures on 6 Pages

Exact Conditions for Ensemble Density Functional Theory

Authors: Thais R. Scott, John Kozlowski, Steven Crisostomo, Aurora Pribram-Jones, Kieron Burke

Abstract: Ensemble density functional theory (EDFT) is a promising alternative to time-dependent density functional theory for computing electronic excitation energies. Using coordinate scaling, we prove several fundamental exact conditions in EDFT and illustrate them on the exact singlet bi-ensemble of the Hubbard dimer. Several approximations violate these conditions, and some ground-state conditions from… ▽ More Ensemble density functional theory (EDFT) is a promising alternative to time-dependent density functional theory for computing electronic excitation energies. Using coordinate scaling, we prove several fundamental exact conditions in EDFT and illustrate them on the exact singlet bi-ensemble of the Hubbard dimer. Several approximations violate these conditions, and some ground-state conditions from quantum chemistry do not generalize to EDFT. The strong-correlation limit is derived for the dimer, revealing weight-dependent derivative discontinuities in EDFT. △ Less

Submitted 30 June, 2023; originally announced July 2023.

Comments: 6 pages 5 figures

Planetary computing for data-driven environmental policy-making

Authors: Patrick Ferris, Michael Dales, Sadiq Jaffer, Amelia Holcomb, Eleanor Toye Scott, Thomas Swinfield, Alison Eyres, Andrew Balmford, David Coomes, Srinivasan Keshav, Anil Madhavapeddy

Abstract: We make a case for "planetary computing" -- infrastructure to handle the ingestion, transformation, analysis and publication of global data products for furthering environmental science and enabling better informed policy-making. We draw on our experiences as a team of computer scientists working with environmental scientists on forest carbon and biodiversity preservation, and classify existing so… ▽ More We make a case for "planetary computing" -- infrastructure to handle the ingestion, transformation, analysis and publication of global data products for furthering environmental science and enabling better informed policy-making. We draw on our experiences as a team of computer scientists working with environmental scientists on forest carbon and biodiversity preservation, and classify existing solutions by their flexibility in scalably processing geospatial data, and also how well they support building trust in the results via traceability and reproducibility. We identify research gaps in the intersection of computing and environmental science around how to handle continuously changing datasets that are often collected across decades and require careful access control rather than being fully open access. △ Less

Submitted 1 June, 2024; v1 submitted 8 March, 2023; originally announced March 2023.

ACM Class: D.0; D.4

Community-developed checklists for publishing images and image analysis

Authors: Christopher Schmied, Michael Nelson, Sergiy Avilov, Gert-Jan Bakker, Cristina Bertocchi, Johanna Bischof, Ulrike Boehm, Jan Brocher, Mariana Carvalho, Catalin Chiritescu, Jana Christopher, Beth Cimini, Eduardo Conde-Sousa, Michael Ebner, Rupert Ecker, Kevin Eliceiri, Julia Fernandez-Rodriguez, Nathalie Gaudreault, Laurent Gelman, David Grunwald, Tingting Gu, Nadia Halidi, Mathias Hammer, Matthew Hartley, Marie Held , et al. (29 additional authors not shown)

Abstract: Images document scientific discoveries and are prevalent in modern biomedical research. Microscopy imaging in particular is currently undergoing rapid technological advancements. However for scientists wishing to publish the obtained images and image analyses results, there are to date no unified guidelines. Consequently, microscopy images and image data in publications may be unclear or difficult… ▽ More Images document scientific discoveries and are prevalent in modern biomedical research. Microscopy imaging in particular is currently undergoing rapid technological advancements. However for scientists wishing to publish the obtained images and image analyses results, there are to date no unified guidelines. Consequently, microscopy images and image data in publications may be unclear or difficult to interpret. Here we present community-developed checklists for preparing light microscopy images and image analysis for publications. These checklists offer authors, readers, and publishers key recommendations for image formatting and annotation, color selection, data availability, and for reporting image analysis workflows. The goal of our guidelines is to increase the clarity and reproducibility of image figures and thereby heighten the quality of microscopy data is in publications. △ Less

Submitted 14 September, 2023; v1 submitted 14 February, 2023; originally announced February 2023.

Comments: 28 pages, 8 Figures, 3 Supplmentary Figures, Manuscript, Essential recommendations for publication of microscopy image data

WALLABY Pilot Survey: Public release of HI kinematic models for more than 100 galaxies from phase 1 of ASKAP pilot observations

Authors: N. Deg, K. Spekkens, T. Westmeier, T. N. Reynolds, P. Venkataraman, S. Goliath, A. X. Shen, R. Halloran, A. Bosma, B. Catinella, W. J. G. de Blok, H. Dénes, E. M. Di Teodoro, A. Elagali, B. -Q. For, C. Howlett, G. I. G. Józsa, P. Kamphuis, D. Kleiner, B. Koribalski, K. Lee-Waddell, F. Lelli, X. Lin, C. Murugeshan, S. Oh , et al. (7 additional authors not shown)

Abstract: We present the Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) Pilot Phase I HI kinematic models. This first data release consists of HI observations of three fields in the direction of the Hydra and Norma clusters, and the NGC 4636 galaxy group. In this paper, we describe how we generate and publicly release flat-disk tilted-ring kinematic models for 109/592 unique HI detections in t… ▽ More We present the Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) Pilot Phase I HI kinematic models. This first data release consists of HI observations of three fields in the direction of the Hydra and Norma clusters, and the NGC 4636 galaxy group. In this paper, we describe how we generate and publicly release flat-disk tilted-ring kinematic models for 109/592 unique HI detections in these fields. The modelling method adopted here - which we call the WALLABY Kinematic Analysis Proto-Pipeline (WKAPP) and for which the corresponding scripts are also publicly available - consists of combining results from the homogeneous application of the FAT and 3DBAROLO algorithms to the subset of 209 detections with sufficient resolution and S/N in order to generate optimized model parameters and uncertainties. The 109 models presented here tend to be gas rich detections resolved by at least 3-4 synthesized beams across their major axes, but there is no obvious environmental bias in the modelling. The data release described here is the first step towards the derivation of similar products for thousands of spatially-resolved WALLABY detections via a dedicated kinematic pipeline. Such a large publicly available and homogeneously analyzed dataset will be a powerful legacy product that that will enable a wide range of scientific studies. △ Less

Submitted 14 November, 2022; originally announced November 2022.

Comments: Accepted to PASA

An Empirical Study on Clustering Pretrained Embeddings: Is Deep Strictly Better?

Authors: Tyler R. Scott, Ting Liu, Michael C. Mozer, Andrew C. Gallagher

Abstract: Recent research in clustering face embeddings has found that unsupervised, shallow, heuristic-based methods -- including $k$-means and hierarchical agglomerative clustering -- underperform supervised, deep, inductive methods. While the reported improvements are indeed impressive, experiments are mostly limited to face datasets, where the clustered embeddings are highly discriminative or well-separ… ▽ More Recent research in clustering face embeddings has found that unsupervised, shallow, heuristic-based methods -- including $k$-means and hierarchical agglomerative clustering -- underperform supervised, deep, inductive methods. While the reported improvements are indeed impressive, experiments are mostly limited to face datasets, where the clustered embeddings are highly discriminative or well-separated by class (Recall@1 above 90% and often nearing ceiling), and the experimental methodology seemingly favors the deep methods. We conduct a large-scale empirical study of 17 clustering methods across three datasets and obtain several robust findings. Notably, deep methods are surprisingly fragile for embeddings with more uncertainty, where they match or even perform worse than shallow, heuristic-based methods. When embeddings are highly discriminative, deep methods do outperform the baselines, consistent with past results, but the margin between methods is much smaller than previously reported. We believe our benchmarks broaden the scope of supervised clustering methods beyond the face domain and can serve as a foundation on which these methods could be improved. To enable reproducibility, we include all necessary details in the appendices, and plan to release the code. △ Less

Submitted 9 November, 2022; originally announced November 2022.

Spatially-resolved properties of early-type group-dominant galaxies with MUSE: gas content, ionisation mechanisms and metallicity gradients

Authors: P. Lagos, S. I. Loubser, T. C. Scott, E. O'Sullivan, K. Kolokythas, A. Babul, A. Nigoche-Netro, V. Olivares, C. Sengupta

Abstract: With the goal of a thorough investigation of the ionised gas and its origin in early-type group-dominant galaxies, we present archival MUSE data for 18 galaxies from the Complete Local-Volume Groups Sample (CLoGS). This data allowed us to study the spatially-resolved warm gas properties, including the morphology of the ionised gas, EW(H$α$) and kinematics as well as the gas-phase metallicity (12 +… ▽ More With the goal of a thorough investigation of the ionised gas and its origin in early-type group-dominant galaxies, we present archival MUSE data for 18 galaxies from the Complete Local-Volume Groups Sample (CLoGS). This data allowed us to study the spatially-resolved warm gas properties, including the morphology of the ionised gas, EW(H$α$) and kinematics as well as the gas-phase metallicity (12 + log(O/H)) of these systems. In order to distinguish between different ionisation mechanisms, we used the emission-line ratios [O III]/H$β$ and [N II]/H$α$ in the BPT diagrams and EW(H$α$). We find that the ionisation sources in our sample have variable impacts at different radii, central regions are more influenced by low-luminosity AGN, while extended regions of LINER-like emission are ionised by other mechanisms with pAGBs photoionisation likely contributing significantly. We classified our sample into three H$α$+[N II] emission morphology types. We calculate the gas-phase metallicity assuming several methods and ionisation sources. In general, 12 + log(O/H) decreases with radius from the centre for all galaxies, independently of nebular morphology type, indicating a metallicity gradient in the abundance profiles. Interestingly, the more extended filamentary structures and all extranuclear star-forming regions present shallow metallicity gradients. Within the uncertainties these extended structures can be considered chemically homogeneous. We suggest that group-dominant galaxies in our sample likely acquired their cold gas in the past as a consequence of one or more mechanisms, e.g. gas-clouds or satellite mergers/accretion and/or cooling flows that contribute to the growth of the ionised gas structures. △ Less

Submitted 30 August, 2022; originally announced August 2022.

Comments: Accepted for publication in MNRAS

HIPASS study of southern ultradiffuse galaxies and low surface brightness galaxies

Authors: Yun-Fan Zhou, Chandreyee Sengupta, Yogesh Chandola, O. Ivy Wong, Tom C. Scott, Yin-Zhe Ma, Hao Chen

Abstract: We present results from an HI counterpart search using the HI Parkes All Sky Survey (HIPASS) for a sample of low surface brightness galaxies (LSBGs) and ultradiffuse galaxies (UDGs) identified from the Dark Energy Survey (DES). We aimed to establish the redshifts of the DES LSBGs to determine the UDG fraction and understand their properties. Out of 409 galaxies investigated, none were unambiguousl… ▽ More We present results from an HI counterpart search using the HI Parkes All Sky Survey (HIPASS) for a sample of low surface brightness galaxies (LSBGs) and ultradiffuse galaxies (UDGs) identified from the Dark Energy Survey (DES). We aimed to establish the redshifts of the DES LSBGs to determine the UDG fraction and understand their properties. Out of 409 galaxies investigated, none were unambiguously detected in HI. Our study was significantly hampered by the high spectral rms of HIPASS and thus in this paper we do not make any strong conclusive claims but discuss the main trends and possible scenarios our results reflect. The overwhelming number of non-detections suggest that: (A) Either all the LSBGs in the groups, blue or red, have undergone environment aided pre-processing and are HI deficient or the majority of them are distant galaxies, beyond the HIPASS detection threshold. (B) The sample investigated is most likely dominated by galaxies with HI masses typical of dwarf galaxies. Had there been Milky Way (MW) size (R_e) galaxies in our sample, with proportionate HI content, they would have been detected, even with the limitations imposed by the HIPASS spectral quality. This leads us to infer that if some of the LSBGs have MW size optical diameters, their HI content is possibly in the dwarf range. More sensitive observations using the SKA precursors in future may resolve these questions. △ Less

Submitted 18 August, 2022; originally announced August 2022.

Comments: 8pages, 5 figures, Accepted in MNRAS

The Arecibo Galaxy Environment Survey (AGES) XI: the expanded Abell 1367 field. Data catalogue and HI census over the surveyed volume

Authors: Boris Deshev, Rhys Taylor, Robert Minchin, Tom C. Scott, Elias Brinks

Abstract: Many galaxy properties are known to correlate with the environment in which the galaxies are embedded. Their cold, neutral gas content, usually assessed through 21cm HI observations, is related to many other galaxy properties as it is the underlying fuel for star formation. With its high sensitivity and broad sky coverage the blind Arecibo Galaxy Environment Survey (AGES) survey brings significant… ▽ More Many galaxy properties are known to correlate with the environment in which the galaxies are embedded. Their cold, neutral gas content, usually assessed through 21cm HI observations, is related to many other galaxy properties as it is the underlying fuel for star formation. With its high sensitivity and broad sky coverage the blind Arecibo Galaxy Environment Survey (AGES) survey brings significant improvement to the census of HI properties of galaxies in a wide range of environments, from voids to the core of a massive cluster. Here we present an HI census over a volume of ~44000 Mpc$^{3}$ towards the merging cluster Abell 1367 and the large-scale structure (LSS) surrounding the cluster out to cz = 20000 km/s. The survey is sensitive down to a column density of N$_{HI}$ = 1.5 x 10$^{17}$ cm$^{-2}$ for emission filling the beam and a line width of 10 km/s. As an approximate mass sensitivity limit, a member of A1367 (at a distance of 92 Mpc), containing M$_{HI}$ = 2.7x10$^{8}$ M$_{\odot}$ distributed over a top-hat profile of 50 km/s width would be detected at 4$σ$. The results are analysed in combination with optical spectroscopy data from SDSS which we use to estimate the local galaxy density based on the Voronoi-Delaunay method. In total we detect 457 HI sources, 213 of which are detected for the first time by the AGES survey, 134 of which are presented in this article for the first time. 225 of the detections are in the cluster and 232 in the remaining volume surveyed. Here we present the full catalogue of HI detections and their basic properties, including optical ones. We concentrate on the difference between the cluster and the foreground and background LSS, revealing a continuous correlation of HI detected fraction (and HI deficiency) with local galaxy density, independent of global environment. △ Less

Submitted 27 June, 2022; originally announced June 2022.

Comments: A&A accepted. 18 pages, 9 figures, 6 page appendix

Journal ref: A&A 665, A155 (2022)

Snake net and balloon force with a neural network for detecting multiple phases

Authors: Xiaodong Sun, Huijiong Yang, Nan Wu, T. C. Scott, Jie Zhang, Wanzhou Zhang

Abstract: Unsupervised machine learning applied to the study of phase transitions is an ongoing and interesting research direction. The active contour model, also called the snake model, was initially proposed for target contour extraction in two-dimensional images. In order to obtain a physical phase diagram, the snake model with an artificial neural network is applied in an unsupervised learning way by th… ▽ More Unsupervised machine learning applied to the study of phase transitions is an ongoing and interesting research direction. The active contour model, also called the snake model, was initially proposed for target contour extraction in two-dimensional images. In order to obtain a physical phase diagram, the snake model with an artificial neural network is applied in an unsupervised learning way by the authors of [Phys.Rev.Lett. 120, 176401(2018)]. It guesses the phase boundary as an initial snake and then drives the snake to convergence with forces estimated by the artificial neural network. In this paper, we extend this unsupervised learning method with one contour to a snake net with multiple contours for the purpose of obtaining several phase boundaries in a phase diagram. For the classical Blume-Capel model, the phase diagram containing three and four phases is obtained. Moreover, to overcome the limitations of the initial position and speed up the movement of the snake, the balloon force decaying with the iteration steps is introduced and applied to the snake net structure. Our method is helpful in determining the phase diagram with multiple phases, using just snapshots of configurations from cold atoms or other experiments without knowledge of the phases. △ Less

Submitted 23 February, 2023; v1 submitted 19 May, 2022; originally announced May 2022.

Comments: 13 pages, 15 figures, submitted to PRE

Journal ref: Phys. Rev. E 107, 065303 (2023)

Non-star-forming molecular gas in the Abell 1367 intra-cluster multiphase orphan cloud

Authors: Pavel Jáchym, Ming Sun, Masafumi Yagi, Chong Ge, Rongxin Luo, Françoise Combes, Anežka Kabátová, Jeffrey D. P. Kenney, Tom C. Scott, Elias Brinks

Abstract: We report the detection of CO emission in the recently discovered multiphase isolated gas cloud in the nearby galaxy cluster Abell 1367. The cloud is located about 800 kpc in projection from the center of the cluster and at a projected distance of > 80 kpc from any galaxy. It is the first and the only known isolated intra-cluster cloud detected in X-ray, H$α$, and CO emission. We found a total of… ▽ More We report the detection of CO emission in the recently discovered multiphase isolated gas cloud in the nearby galaxy cluster Abell 1367. The cloud is located about 800 kpc in projection from the center of the cluster and at a projected distance of > 80 kpc from any galaxy. It is the first and the only known isolated intra-cluster cloud detected in X-ray, H$α$, and CO emission. We found a total of about $2.2\times 10^8 M_\odot$ of H$_2$ with the IRAM 30-m telescope in two regions, one associated with the peak of H$α$ emission and another with the peak of X-ray emission surrounded by weak H$α$ filaments. The velocity of the molecular gas is offset from the underlying H$α$ emission by > 100 km s$^{-1}$ in the region where the X-ray peaks. The molecular gas may account for about 10% of the total cloud's mass, which is dominated by the hot X-ray component. The previously measured upper limit on the star formation rate in the cloud indicates that the molecular component is in a non-star-forming state, possibly due to a combination of low density of the gas and the observed level of velocity dispersion. The presence of the three gas phases associated with the cloud suggests that gas phase mixing with the surrounding intra-cluster medium is taking place. The possible origin of the orphan cloud is a late evolutionary stage of a ram pressure stripping event. In contrast, the nearby ram pressure stripped galaxy 2MASX J11443212+2006238 is in an early phase of stripping and we detected about $2.4\times 10^9 M_\odot$ of H$_2$ in its main body. △ Less

Submitted 26 January, 2022; originally announced January 2022.

Comments: Accepted for publication in A&A Letters

Journal ref: A&A 658, L5 (2022)

FGC 1287 and its enigmatic 250 kpc long HI tail in the outskirts of Abell 1367

Authors: T. C. Scott, L. Cortese, P. Lagos, E. Brinks, A. Finoguenov, L. Coccato

Abstract: We present HI and radio continuum, narrow-band H$α$ imaging, IFU spectroscopy, and X-ray observations of the FGC 1287 triplet projected $\sim$ 1.8 Mpc west of the galaxy cluster Abell 1367. One triplet member, FGC 1287, displays an exceptionally long, 250 kpc HI tail and an unperturbed stellar disk which are the typical signatures of ram pressure stripping (RPS). To generate detectable RPS signatu… ▽ More We present HI and radio continuum, narrow-band H$α$ imaging, IFU spectroscopy, and X-ray observations of the FGC 1287 triplet projected $\sim$ 1.8 Mpc west of the galaxy cluster Abell 1367. One triplet member, FGC 1287, displays an exceptionally long, 250 kpc HI tail and an unperturbed stellar disk which are the typical signatures of ram pressure stripping (RPS). To generate detectable RPS signatures the presence of an Intra-cluster medium (ICM)/intra-group medium (IGM) with sufficient density to produce RPS at a realistic velocity relative to the ICM/IGM is a prerequisite. However, XMM-Newton observations were not able to detect X-ray emission from the triplet, implying that if a hot ICM/IGM is present, its density, n${_e}$, is less than 2.6 $\times$ 10$^{-5}$ cm$^{-3}$. Higher-resolution VLA HI data presented here show FGC 1287's HI disk is truncated and significantly warped whereas the HI tail is clumpy. TNG H$α$ imaging identified three star forming clumps projected within 20 kpc of FGC 1287's disk, with VIMOS-IFU data confirming two of these are counterparts to HI clumps in the tail. The triplet's HI kinematics, together with H$α$ and radio continuum imaging suggests an interaction may have enhanced star formation in FGC 1287's disk, but cannot readily account for the origin of the long HI tail. We consider several scenarios which might reconcile RPS with the non-detection of ICM/IGM X-ray emission but none of these unambiguously explains the origin of the long HI tail. △ Less

Submitted 12 January, 2022; originally announced January 2022.

Comments: 15 pages, 11 figures

Beyond Low Earth Orbit: Biological Research, Artificial Intelligence, and Self-Driving Labs

Authors: Lauren M. Sanders, Jason H. Yang, Ryan T. Scott, Amina Ann Qutub, Hector Garcia Martin, Daniel C. Berrios, Jaden J. A. Hastings, Jon Rask, Graham Mackintosh, Adrienne L. Hoarfrost, Stuart Chalk, John Kalantari, Kia Khezeli, Erik L. Antonsen, Joel Babdor, Richard Barker, Sergio E. Baranzini, Afshin Beheshti, Guillermo M. Delgado-Aparicio, Benjamin S. Glicksberg, Casey S. Greene, Melissa Haendel, Arif A. Hamid, Philip Heller, Daniel Jamieson , et al. (31 additional authors not shown)

Abstract: Space biology research aims to understand fundamental effects of spaceflight on organisms, develop foundational knowledge to support deep space exploration, and ultimately bioengineer spacecraft and habitats to stabilize the ecosystem of plants, crops, microbes, animals, and humans for sustained multi-planetary life. To advance these aims, the field leverages experiments, platforms, data, and mode… ▽ More Space biology research aims to understand fundamental effects of spaceflight on organisms, develop foundational knowledge to support deep space exploration, and ultimately bioengineer spacecraft and habitats to stabilize the ecosystem of plants, crops, microbes, animals, and humans for sustained multi-planetary life. To advance these aims, the field leverages experiments, platforms, data, and model organisms from both spaceborne and ground-analog studies. As research is extended beyond low Earth orbit, experiments and platforms must be maximally autonomous, light, agile, and intelligent to expedite knowledge discovery. Here we present a summary of recommendations from a workshop organized by the National Aeronautics and Space Administration on artificial intelligence, machine learning, and modeling applications which offer key solutions toward these space biology challenges. In the next decade, the synthesis of artificial intelligence into the field of space biology will deepen the biological understanding of spaceflight effects, facilitate predictive modeling and analytics, support maximally autonomous and reproducible experiments, and efficiently manage spaceborne data and metadata, all with the goal to enable life to thrive in deep space. △ Less

Submitted 22 December, 2021; originally announced December 2021.

Comments: 28 pages, 4 figures

Beyond Low Earth Orbit: Biomonitoring, Artificial Intelligence, and Precision Space Health

Authors: Ryan T. Scott, Erik L. Antonsen, Lauren M. Sanders, Jaden J. A. Hastings, Seung-min Park, Graham Mackintosh, Robert J. Reynolds, Adrienne L. Hoarfrost, Aenor Sawyer, Casey S. Greene, Benjamin S. Glicksberg, Corey A. Theriot, Daniel C. Berrios, Jack Miller, Joel Babdor, Richard Barker, Sergio E. Baranzini, Afshin Beheshti, Stuart Chalk, Guillermo M. Delgado-Aparicio, Melissa Haendel, Arif A. Hamid, Philip Heller, Daniel Jamieson, Katelyn J. Jarvis , et al. (31 additional authors not shown)

Abstract: Human space exploration beyond low Earth orbit will involve missions of significant distance and duration. To effectively mitigate myriad space health hazards, paradigm shifts in data and space health systems are necessary to enable Earth-independence, rather than Earth-reliance. Promising developments in the fields of artificial intelligence and machine learning for biology and health can address… ▽ More Human space exploration beyond low Earth orbit will involve missions of significant distance and duration. To effectively mitigate myriad space health hazards, paradigm shifts in data and space health systems are necessary to enable Earth-independence, rather than Earth-reliance. Promising developments in the fields of artificial intelligence and machine learning for biology and health can address these needs. We propose an appropriately autonomous and intelligent Precision Space Health system that will monitor, aggregate, and assess biomedical statuses; analyze and predict personalized adverse health outcomes; adapt and respond to newly accumulated data; and provide preventive, actionable, and timely insights to individual deep space crew members and iterative decision support to their crew medical officer. Here we present a summary of recommendations from a workshop organized by the National Aeronautics and Space Administration, on future applications of artificial intelligence in space biology and health. In the next decade, biomonitoring technology, biomarker science, spacecraft hardware, intelligent software, and streamlined data management must mature and be woven together into a Precision Space Health system to enable humanity to thrive in deep space. △ Less

Submitted 22 December, 2021; originally announced December 2021.

Comments: 31 pages, 4 figures

Online Unsupervised Learning of Visual Representations and Categories

Authors: Mengye Ren, Tyler R. Scott, Michael L. Iuzzolino, Michael C. Mozer, Richard Zemel

Abstract: Real world learning scenarios involve a nonstationary distribution of classes with sequential dependencies among the samples, in contrast to the standard machine learning formulation of drawing samples independently from a fixed, typically uniform distribution. Furthermore, real world interactions demand learning on-the-fly from few or no class labels. In this work, we propose an unsupervised mode… ▽ More Real world learning scenarios involve a nonstationary distribution of classes with sequential dependencies among the samples, in contrast to the standard machine learning formulation of drawing samples independently from a fixed, typically uniform distribution. Furthermore, real world interactions demand learning on-the-fly from few or no class labels. In this work, we propose an unsupervised model that simultaneously performs online visual representation learning and few-shot learning of new categories without relying on any class labels. Our model is a prototype-based memory network with a control component that determines when to form a new class prototype. We formulate it as an online mixture model, where components are created with only a single new example, and assignments do not have to be balanced, which permits an approximation to natural imbalanced distributions from uncurated raw data. Learning includes a contrastive loss that encourages different views of the same image to be assigned to the same prototype. The result is a mechanism that forms categorical representations of objects in nonstationary environments. Experiments show that our method can learn from an online stream of visual input data and its learned representations are significantly better at category recognition compared to state-of-the-art self-supervised learning methods. △ Less

Submitted 28 May, 2022; v1 submitted 12 September, 2021; originally announced September 2021.

Comments: Technical report, 32 pages

WALLABY pre-pilot survey: Two dark clouds in the vicinity of NGC 1395

Authors: O. Ivy Wong, A. R. H. Stevens, B. -Q. For, T. Westmeier, M. Dixon, S. -H. Oh, G. I. G. Józsa, T. N. Reynolds, K. Lee-Waddell, J. Román, L. Verdes-Montenegro, H. M. Courtois, D. Pomarède, C. Murugeshan, M. T. Whiting, K. Bekki, F. Bigiel, A. Bosma, B. Catinella, H. Dénes, A. Elagali, B. W. Holwerda, P. Kamphuis, V. A. Kilborn, D. Kleiner , et al. (12 additional authors not shown)

Abstract: We present the Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pre-pilot observations of two `dark' HI sources (with HI masses of a few times 10^8 Msol and no known stellar counterpart) that reside within 363 kpc of NGC 1395, the most massive early-type galaxy in the Eridanus group of galaxies. We investigate whether these `dark' HI sources have resulted from past tidal interactions o… ▽ More We present the Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pre-pilot observations of two `dark' HI sources (with HI masses of a few times 10^8 Msol and no known stellar counterpart) that reside within 363 kpc of NGC 1395, the most massive early-type galaxy in the Eridanus group of galaxies. We investigate whether these `dark' HI sources have resulted from past tidal interactions or whether they are an extreme class of low surface brightness galaxies. Our results suggest that both scenarios are possible, and not mutually exclusive. The two `dark' HI sources are compact, reside in relative isolation and are more than 159 kpc away from their nearest HI-rich galaxy neighbour. Regardless of origin, the HI sizes and masses of both `dark' HI sources are consistent with the HI size-mass relationship that is found in nearby low-mass galaxies, supporting the possibility that these HI sources are an extreme class of low surface brightness galaxies. We identified three analogues of candidate primordial `dark' HI galaxies within the TNG100 cosmological, hydrodynamic simulation. All three model analogues are dark matter-dominated, have assembled most of their mass 12-13 Gyr ago, and have not experienced much evolution until cluster infall 1-2 Gyr ago. Our WALLABY pre-pilot science results suggest that the upcoming large area HI surveys will have a significant impact on our understanding of low surface brightness galaxies and the physical processes that shape them. △ Less

Submitted 9 August, 2021; originally announced August 2021.

Comments: 16 pages, 11 figures, accepted for publication in MNRAS

Self-consistent population spectral synthesis with FADO: II. Star formation history of galaxies in spectral synthesis methods

Authors: Ciro Pappalardo, Leandro S. M. Cardoso, Jean Michel Gomes, Polychronis Papaderos, José Afonso, Iris Breda, Andrew Humphrey, Tom Scott, Stergios Amarantidis, Israel Matute, Rodrigo Carvajal, Silvio Lorenzoni, Patricio Lagos, Ana Paulino-Afonso, Henrique Miranda

Abstract: The field of galaxy evolution will make a great leap forward in the next decade as a consequence of the huge effort by the scientific community in multi-object spectroscopic facilities. To maximise the impact of such incoming data, the analysis methods must also step up, extracting reliable information from the available spectra. In this paper, we aim to investigate the limits and the reliability… ▽ More The field of galaxy evolution will make a great leap forward in the next decade as a consequence of the huge effort by the scientific community in multi-object spectroscopic facilities. To maximise the impact of such incoming data, the analysis methods must also step up, extracting reliable information from the available spectra. In this paper, we aim to investigate the limits and the reliability of different spectral synthesis methods in the estimation of the mean stellar age and metallicity. The main question this work aims to address is which signal-to-noise ratios (S/N) are needed to reliably determine the mean stellar age and metallicity from a galaxy spectrum and how this depends on the tool used to model the spectra. To address this question we built a set of realistic simulated spectra containing stellar and nebular emission, reproducing the evolution of a galaxy in two limiting cases: a constant star formation rate and an exponentially declining star formation. We degraded the synthetic spectra built from these two star formation histories (SFHs) to different S/N and analysed them with three widely used spectral synthesis codes, namely FADO, STECKMAP, and STARLIGHT. For S/N < 5 all three tools show a large diversity in the results. The FADO and STARLIGHT tools find median differences in the light-weighted mean stellar age of ~0.1 dex, while STECKMAP shows a higher value of ~0.2 dex. Detailed investigations of the best-fit spectrum for galaxies with overestimated mass-weighted quantities point towards the inability of purely stellar models to fit the observed spectra around the Balmer jump. Our results imply that when a galaxy enters a phase of high specific star formation rate the neglect of the nebular continuum emission in the fitting process has a strong impact on the estimation of its SFH when purely stellar fitting codes are used, even in presence of high S/N spectra. △ Less

Submitted 15 September, 2021; v1 submitted 17 May, 2021; originally announced May 2021.

Comments: New version matching the published one. 19 pages, 16 figures, accepted for publication in A&A

Journal ref: A&A 651, A99 (2021)

von Mises-Fisher Loss: An Exploration of Embedding Geometries for Supervised Learning

Authors: Tyler R. Scott, Andrew C. Gallagher, Michael C. Mozer

Abstract: Recent work has argued that classification losses utilizing softmax cross-entropy are superior not only for fixed-set classification tasks, but also by outperforming losses developed specifically for open-set tasks including few-shot learning and retrieval. Softmax classifiers have been studied using different embedding geometries -- Euclidean, hyperbolic, and spherical -- and claims have been mad… ▽ More Recent work has argued that classification losses utilizing softmax cross-entropy are superior not only for fixed-set classification tasks, but also by outperforming losses developed specifically for open-set tasks including few-shot learning and retrieval. Softmax classifiers have been studied using different embedding geometries -- Euclidean, hyperbolic, and spherical -- and claims have been made about the superiority of one or another, but they have not been systematically compared with careful controls. We conduct an empirical investigation of embedding geometry on softmax losses for a variety of fixed-set classification and image retrieval tasks. An interesting property observed for the spherical losses lead us to propose a probabilistic classifier based on the von Mises-Fisher distribution, and we show that it is competitive with state-of-the-art methods while producing improved out-of-the-box calibration. We provide guidance regarding the trade-offs between losses and how to choose among them. △ Less

Submitted 3 December, 2021; v1 submitted 29 March, 2021; originally announced March 2021.

Comments: ICCV 2021

Resolved HI in two ultra-diffuse galaxies from contrasting non-cluster environments

Authors: T. C. Scott, Chandreyee Sengupta, P. Lagos, Aeree Chung, O. Ivy Wong

Abstract: We report on the first resolved HI observations of two blue ultra-diffuse galaxies (UDGs)using the Giant Metrewave Radio Telescope (GMRT). These observations add to the sofar limited number of UDGs with resolved HI data. The targets are from contrasting non-cluster environments: UDG-B1 is projected in the outskirts of Hickson Compact Group 25 and Secco-dI-2 (SdI-2) is an isolated UDG. These UDGs a… ▽ More We report on the first resolved HI observations of two blue ultra-diffuse galaxies (UDGs)using the Giant Metrewave Radio Telescope (GMRT). These observations add to the sofar limited number of UDGs with resolved HI data. The targets are from contrasting non-cluster environments: UDG-B1 is projected in the outskirts of Hickson Compact Group 25 and Secco-dI-2 (SdI-2) is an isolated UDG. These UDGs also have contrasting effective radii with Re of 3.7 kpc (similar to the Milky Way) and 1.3 kpc respectively. SdI-2 has an unusually large MHI/M* ratio =28.9, confirming a previous single dish HI observation. Both galaxies display HI morphological and kinematic signatures consistent with a recent tidal interaction, which is also supported by observations from other wavelengths, including optical spectroscopy. Within the limits of the observations' resolution, our analysis indicates that SdI-2 is dark matter-dominated within its HI radius and this is also likely to be the case for UDG-B1. Our study highlights the importance of high spatial and spectral resolution HI observations for the study of the dark matter properties of UDGs. △ Less

Submitted 8 February, 2021; originally announced February 2021.

Comments: 13 pages , 8 Figures

Interacting system NGC 7805/6 (Arp 112) and its tidal dwarf galaxy candidate

Authors: ZhenXing Fu, Chandreyee Sengupta, Ramya Sethuram, Bikram Pradhan, Mridweeka Singh, Kuntal Misra, Tom C. Scott, Yin-Zhe Ma

Abstract: We present results from our Giant Metrewave Radio Telescope (GMRT) HI, Himalayan Chandra Telescope (HCT) Halpha, 1m Sampurnanand Telescope (ST) and 1.3m Devasthal Fast Optical Telescope (DFOT) deep optical observations of NGC 7805/6 (Arp 112) system to test KUG 2359+311's tidal dwarf galaxy (TDG) candidacy and explore the properties of the interacting system. Our GMRT HI map shows no HI detection… ▽ More We present results from our Giant Metrewave Radio Telescope (GMRT) HI, Himalayan Chandra Telescope (HCT) Halpha, 1m Sampurnanand Telescope (ST) and 1.3m Devasthal Fast Optical Telescope (DFOT) deep optical observations of NGC 7805/6 (Arp 112) system to test KUG 2359+311's tidal dwarf galaxy (TDG) candidacy and explore the properties of the interacting system. Our GMRT HI map shows no HI detection associated with KUG 2359+311, nor any HI tail or bridge-like structure connecting KUG 2359+311 to the NGC 7805/6 system. Our HCT Halpha image on the other hand, shows strong detections in KUG 2359+311, with net SFR ~ 0.035$\pm 0.009 {\rm M}_{\odot}\,{\rm yr}^{-1}$. The Halpha data constrains the redshift of KUG 2359+311 to $0.00 \le z \le 0.043$, compared to the redshift of NGC 7806 of ~ 0.015. TDGs detected to date have all been HI rich, and displayed HI, ionised gas and stellar tidal debris trails (bridges or tails) linking them to their parent systems. But neither our HI data nor our optical images, while three magnitudes deeper than SDSS, reveal tidal trail connecting KUG 2359+311 to NGC 7805/6. Lack of HI , presence of an old stellar population, ongoing star formation, reasonably high SFR compared to normal dwarf galaxies suggest that KUG 2359+311 may not be an Arp 112 TDG. It is most likely a case of a regular gas-rich dwarf galaxy undergoing a morphological transformation after having lost its entire gas content to an interaction with the Arp 112 system. Redshift and metallicity from future spectroscopic observations of KUG 2359+311 would help clarify the nature of this enigmatic structure. △ Less

Submitted 12 November, 2020; originally announced November 2020.

Comments: Accepted in RAA

Surfacing Misconceptions Through Visualization Critique

Authors: Amy Rae Fox, Taylor Jackson Scott

Abstract: Students of visualization come to formal education with an abundance of personal experience. However, one's exposure to graphics through media and education may not be sufficiently diverse to appreciate the nuance and complexity required to design and evaluate effective representations. While many introductory courses in visualization address best practices for visual encoding of data based on per… ▽ More Students of visualization come to formal education with an abundance of personal experience. However, one's exposure to graphics through media and education may not be sufficiently diverse to appreciate the nuance and complexity required to design and evaluate effective representations. While many introductory courses in visualization address best practices for visual encoding of data based on perceptual characteristics, as cognitive scientists, we place equal value on representational decisions based on communicative context: how the representation is intended to be used. In this pedagogical activity, we aim to surface learners' preconceived notions about what makes a visualization effective. Here we describe the structure and context of an introductory-level visualization activity, how it might be conducted in individual or group settings, our experience with the common misconceptions the activity can reveal, and conclude with recommendations on how they might be addressed. △ Less

Submitted 7 October, 2020; originally announced October 2020.

Worm quantum Monte-Carlo study of phase diagram of extended Jaynes-Cummings-Hubbard model

Authors: Huanhuan Wei, Jie Zhang, Sebastian Greschner, Tony C Scott, Wanzhou Zhang

Abstract: Herein, we study the extended Jaynes-Cummings-Hubbard model mainly by the large-scale worm quantum Monte-Carlo method to check whether or not a light supersolid phase exists in various geometries, such as the one-dimensional chain, square lattices and triangular lattices. To achieve our purpose, the ground state phase diagrams are investigated. For the one-dimensional chain and square lattices, a… ▽ More Herein, we study the extended Jaynes-Cummings-Hubbard model mainly by the large-scale worm quantum Monte-Carlo method to check whether or not a light supersolid phase exists in various geometries, such as the one-dimensional chain, square lattices and triangular lattices. To achieve our purpose, the ground state phase diagrams are investigated. For the one-dimensional chain and square lattices, a first-order transition occurs between the superfluid phase and the solid phase and therefore there is no stable supersolid phase existing in these geometries. Interestingly, soliton/beats of the local densities arise if the chemical potential is adjusted in the finite-size chain. However, this soliton-superfluid coexistence can not be considered as a supersolid in the thermodynamic limit. Searching for a light supersolid, we also studied the Jaynes-Cummings-Hubbard model on triangular lattices, and the phase diagrams are obtained. Through measurement of the structural factor, momentum distribution and superfluid stiffness for various system sizes, a supersolid phase exists stably in the triangular lattices geometry and the regime of the supersolid phase is smaller than that of the mean field results. The light supersolid in the Jaynes-Cummings-Hubbard model is attractive because it has superreliance, which is absent in the pure Bose-Hubbard model. We believe the results in this paper could help search for new novel phases in cold-atom experiments △ Less

Submitted 5 October, 2020; originally announced October 2020.

Comments: 10 pages, 13 figures

Journal ref: Phys. Rev. B 103, 184501 (2021)

Unifying Few- and Zero-Shot Egocentric Action Recognition

Authors: Tyler R. Scott, Michael Shvartsman, Karl Ridgeway

Abstract: Although there has been significant research in egocentric action recognition, most methods and tasks, including EPIC-KITCHENS, suppose a fixed set of action classes. Fixed-set classification is useful for benchmarking methods, but is often unrealistic in practical settings due to the compositionality of actions, resulting in a functionally infinite-cardinality label set. In this work, we explore… ▽ More Although there has been significant research in egocentric action recognition, most methods and tasks, including EPIC-KITCHENS, suppose a fixed set of action classes. Fixed-set classification is useful for benchmarking methods, but is often unrealistic in practical settings due to the compositionality of actions, resulting in a functionally infinite-cardinality label set. In this work, we explore generalization with an open set of classes by unifying two popular approaches: few- and zero-shot generalization (the latter which we reframe as cross-modal few-shot generalization). We propose a new set of splits derived from the EPIC-KITCHENS dataset that allow evaluation of open-set classification, and use these splits to show that adding a metric-learning loss to the conventional direct-alignment baseline can improve zero-shot classification by as much as 10%, while not sacrificing few-shot performance. △ Less

Submitted 26 May, 2020; originally announced June 2020.

Comments: Accepted for presentation at the EPIC@CVPR2020 workshop

Resolving the puzzle of sound propagation in liquid helium at low temperatures

Authors: Tony C. Scott, Konstantin G. Zloshchastiev

Abstract: Experimental data suggests that, at temperatures below 1 K, the pressure in liquid helium has a cubic dependence on density. Thus the speed of sound scales as a cubic root of pressure. Near a critical pressure point, this speed approaches zero whereby the critical pressure is negative, thus indicating a cavitation instability regime. We demonstrate that to explain this dependence, one has to view… ▽ More Experimental data suggests that, at temperatures below 1 K, the pressure in liquid helium has a cubic dependence on density. Thus the speed of sound scales as a cubic root of pressure. Near a critical pressure point, this speed approaches zero whereby the critical pressure is negative, thus indicating a cavitation instability regime. We demonstrate that to explain this dependence, one has to view liquid helium as a mixture of three quantum Bose liquids: dilute (Gross-Pitaevskii-type) Bose-Einstein condensate, Ginzburg-Sobyanin-type fluid, and logarithmic superfluid. Therefore, the dynamics of such a mixture is described by a quantum wave equation, which contains not only the polynomial (Gross-Pitaevskii and Ginzburg-Sobyanin) nonlinearities with respect to a condensate wavefunction, but also a non-polynomial logarithmic nonlinearity. We derive an equation of state and speed of sound in our model, and show their agreement with experiment. △ Less

Submitted 16 June, 2020; originally announced June 2020.

Comments: 5 pages, 3 figures, final/published version

Journal ref: Low Temp. Phys. 45, 1231 (2019)

The ARF-AID system: Methods that preserve endogenous protein levels and facilitate rapidly inducible protein degradation

Authors: Kizhakke Mattada Sathyan, Thomas G. Scott, Michael J. Guertin

Abstract: The ARF-AID (Auxin Response Factor-Auxin Inducible Degron) system is a re-engineered auxin-inducible protein degradation system. Inducible degron systems are widely used to specifically and rapidly deplete proteins of interest in cell lines and organisms. An advantage of inducible degradation is that the biological system under study remains intact and functional until perturbation. This feature n… ▽ More The ARF-AID (Auxin Response Factor-Auxin Inducible Degron) system is a re-engineered auxin-inducible protein degradation system. Inducible degron systems are widely used to specifically and rapidly deplete proteins of interest in cell lines and organisms. An advantage of inducible degradation is that the biological system under study remains intact and functional until perturbation. This feature necessitates that the endogenous levels of the protein are maintained. However, endogenous tagging of genes with AID can result in chronic, auxin-independent proteasome-mediated degradation. The additional expression of the ARF-PB1 domain in the re-engineered ARF-AID system prevents chronic degradation of AID-tagged proteins while preserving rapid degradation of tagged proteins. Here we describe the protocol for engineering human cell lines to implement the ARF-AID system for specific and inducible protein degradation. These methods are adaptable and can be extended from cell lines to organisms. △ Less

Submitted 28 February, 2020; originally announced February 2020.

Comments: 43 pages, 8 figures

Structural analysis of massive galaxies using HST deep imaging at z < 0.5

Authors: Sandra N. dos Reis, Fernando Buitrago, Polychronis Papaderos, Israel Matute, José Afonso, Stergios Amarantidis, Iris Breda, Jean M. Gomes, Andrew Humphrey, Catarina Lobo, Silvio Lorenzoni, Cirino Pappalardo, Ana Paulino-Afonso, Tom Scott

Abstract: Taking advantage of HST CANDELS data, we analyze the lowest redshift (z<0.5) massive galaxies in order to disentangle their structural constituents and study possible faint non-axis-symmetric features. Due to the excellent HST spatial resolution for intermediate-z objects, they are hard to model by purely automatic parametric fitting algorithms. We performed careful single and double Sérsic fits t… ▽ More Taking advantage of HST CANDELS data, we analyze the lowest redshift (z<0.5) massive galaxies in order to disentangle their structural constituents and study possible faint non-axis-symmetric features. Due to the excellent HST spatial resolution for intermediate-z objects, they are hard to model by purely automatic parametric fitting algorithms. We performed careful single and double Sérsic fits to their galaxy surface brightness profiles. We also compare the model color profiles with the observed ones and also derive multi-component global effective radii attempting to obtain a better interpretation of the mass-size relation. Additionally, we test the robustness of our measured structural parameters via simulations. We find that the Sérsic index does not offer a good proxy for the visual morphological type for our sample of massive galaxies. Our derived multi-component effective radii give a better description of the size of our sample galaxies than those inferred from single Sérsic models with GALFIT. Our galaxy population lays on the scatter of the local mass-size relation, indicating that these massive galaxies do not experience a significant growth in size since z~0.5. Interestingly the few outliers are late-type galaxies, indicating that spheroids must reach the local mass-size relation earlier. For most of our sample galaxies, both single and multi-component Sérsic models with GALFIT show substantial systematic deviations from the observed SBPs in the outskirts. These residuals may be partly due to several factors, namely a non-optimal data reduction for low surface brightness features, the existence of prominent stellar haloes for massive galaxies and could also arise from conceptual shortcomings of parametric 2D image decomposition tools. They consequently propagate into galaxy color profiles. △ Less

Submitted 27 November, 2019; originally announced November 2019.

Journal ref: A&A 634, A11 (2020)

Geomorphological Analysis Using Unpiloted Aircraft Systems, Structure from Motion, and Deep Learning

Authors: Zhiang Chen, Tyler R. Scott, Sarah Bearman, Harish Anand, Devin Keating, Chelsea Scott, J Ramon Arrowsmith, Jnaneshwar Das

Abstract: We present a pipeline for geomorphological analysis that uses structure from motion (SfM) and deep learning on close-range aerial imagery to estimate spatial distributions of rock traits (size, roundness, and orientation) along a tectonic fault scarp. The properties of the rocks on the fault scarp derive from the combination of initial volcanic fracturing and subsequent tectonic and geomorphic fra… ▽ More We present a pipeline for geomorphological analysis that uses structure from motion (SfM) and deep learning on close-range aerial imagery to estimate spatial distributions of rock traits (size, roundness, and orientation) along a tectonic fault scarp. The properties of the rocks on the fault scarp derive from the combination of initial volcanic fracturing and subsequent tectonic and geomorphic fracturing, and our pipeline allows scientists to leverage UAS-based imagery to gain a better understanding of such surface processes. We start by using SfM on aerial imagery to produce georeferenced orthomosaics and digital elevation models (DEM). A human expert then annotates rocks on a set of image tiles sampled from the orthomosaics, and these annotations are used to train a deep neural network to detect and segment individual rocks in the entire site. The extracted semantic information (rock masks) on large volumes of unlabeled, high-resolution SfM products allows subsequent structural analysis and shape descriptors to estimate rock size, roundness, and orientation. We present results of two experiments conducted along a fault scarp in the Volcanic Tablelands near Bishop, California. We conducted the first, proof-of-concept experiment with a DJI Phantom 4 Pro equipped with an RGB camera and inspected if elevation information assisted instance segmentation from RGB channels. Rock-trait histograms along and across the fault scarp were obtained with the neural network inference. In the second experiment, we deployed a hexrotor and a multispectral camera to produce a DEM and five spectral orthomosaics in red, green, blue, red edge, and near infrared. We focused on examining the effectiveness of different combinations of input channels in instance segmentation. △ Less

Submitted 17 February, 2021; v1 submitted 27 September, 2019; originally announced September 2019.

Journal ref: 2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

Stochastic Prototype Embeddings

Authors: Tyler R. Scott, Karl Ridgeway, Michael C. Mozer

Abstract: Supervised deep-embedding methods project inputs of a domain to a representational space in which same-class instances lie near one another and different-class instances lie far apart. We propose a probabilistic method that treats embeddings as random variables. Extending a state-of-the-art deterministic method, Prototypical Networks (Snell et al., 2017), our approach supposes the existence of a c… ▽ More Supervised deep-embedding methods project inputs of a domain to a representational space in which same-class instances lie near one another and different-class instances lie far apart. We propose a probabilistic method that treats embeddings as random variables. Extending a state-of-the-art deterministic method, Prototypical Networks (Snell et al., 2017), our approach supposes the existence of a class prototype around which class instances are Gaussian distributed. The prototype posterior is a product distribution over labeled instances, and query instances are classified by marginalizing relative prototype proximity over embedding uncertainty. We describe an efficient sampler for approximate inference that allows us to train the model at roughly the same space and time cost as its deterministic sibling. Incorporating uncertainty improves performance on few-shot learning and gracefully handles label noise and out-of-distribution inputs. Compared to the state-of-the-art stochastic method, Hedged Instance Embeddings (Oh et al., 2019), we achieve superior large- and open-set classification accuracy. Our method also aligns class-discriminating features with the axes of the embedding space, yielding an interpretable, disentangled representation. △ Less

Submitted 25 September, 2019; originally announced September 2019.

Comments: 15 pages, 8 figures

Dark Matter and HI in Ultra-Diffuse Galaxy UGC 2162

Authors: Chandreyee Sengupta, T. C. Scott, Aeree Chung, O. Ivy Wong

Abstract: Our GMRT HI observations of the ultra diffuse galaxy (UDG) UGC 2162, projected $\sim$ 300 kpc from the centre of the M77 group, reveal it to a have an extended HI disk (R$_{HI}$/R$_{25}$ $\sim$ 3.3) with a moderate rotational velocity (V$_{rot} \sim$ 31 km/s). This V$_{rot}$ is in line with that of dwarf galaxies with similar HI mass. We estimate an M$_{dyn}$ of $\sim$ 1.14 $\times$ 10$^{9}$ M… ▽ More Our GMRT HI observations of the ultra diffuse galaxy (UDG) UGC 2162, projected $\sim$ 300 kpc from the centre of the M77 group, reveal it to a have an extended HI disk (R$_{HI}$/R$_{25}$ $\sim$ 3.3) with a moderate rotational velocity (V$_{rot} \sim$ 31 km/s). This V$_{rot}$ is in line with that of dwarf galaxies with similar HI mass. We estimate an M$_{dyn}$ of $\sim$ 1.14 $\times$ 10$^{9}$ M$_\odot$ within the galaxy's R$_{HI}$ $\sim$ 5.2 kpc. Additionally, our estimates of M$_{200}$ for the galaxy from NFW models are in the range of 5.0 to 8.8 $\times$ 10$^{10}$ M$_\odot$. Comparing UGC 2162 to samples of UDGs with HI detections show it to have amongst the smallest R$_e$ with its M$_{HI}$/M$_{\star}$ being distinctly higher and g -- i colour slightly bluer than typical values in those samples. We also compared HI and dark matter (DM) halo properties of UGC 2162 with dwarf galaxies in the LITTLE THINGS sample and find its DM halo mass and profile are within the range expected for a dwarf galaxy. While we were unable to to determine the origin of the galaxy's present day optical form from our study, its normal HI rotation velocity in relation to its HI mass, HI morphology, environment and dwarf mass DM halo ruled out some of the proposed ultra diffuse galaxy formation scenarios for this galaxy. △ Less

Submitted 24 July, 2019; originally announced July 2019.

Comments: Accepted in MNRAS

Impact of Stellar Superflares on Planetary Habitability

Authors: Yosuke A. Yamashiki, Hiroyuki Maehara, Vladimir Airapetian, Yuta Notsu, Tatsuhiko Sato, Shota Notsu, Ryusuke Kuroki, Keiya Murashima, Hiroaki Sato, Kosuke Namekata, Takanori Sasaki, Thomas B. Scott, Hina Bando, Subaru Nashimoto, Fuka Takagi, Cassandra Ling, Daisaku Nogami, Kazunari Shibata

Abstract: High-energy radiation caused by exoplanetary space weather events from planet-hosting stars can play a crucial role in conditions promoting or destroying habitability in addition to the conventional factors. In this paper, we present the first quantitative impact evaluation system of stellar flares on the habitability factors with an emphasis on the impact of Stellar Proton Events. We derive the m… ▽ More High-energy radiation caused by exoplanetary space weather events from planet-hosting stars can play a crucial role in conditions promoting or destroying habitability in addition to the conventional factors. In this paper, we present the first quantitative impact evaluation system of stellar flares on the habitability factors with an emphasis on the impact of Stellar Proton Events. We derive the maximum flare energy from stellar starspot sizes and examine the impacts of flare associated ionizing radiation on CO$_2$, H$_2$, N$_2$+O$_2$ --rich atmospheres of a number of well-characterized terrestrial type exoplanets. Our simulations based on the Particle and Heavy Ion Transport code System [PHITS] suggest that the estimated ground level dose for each planet in the case of terrestrial-level atmospheric pressure (1 bar) for each exoplanet does not exceed the critical dose for complex (multi-cellular) life to persist, even for the planetary surface of Proxima Centauri b, Ross-128 b and TRAPPIST-1 e. However, when we take into account the effects of the possible maximum flares from those host stars, the estimated dose reaches fatal levels at the terrestrial lowest atmospheric depth on TRAPPIST-1 e and Ross-128 b. Large fluxes of coronal XUV radiation from active stars induces high atmospheric escape rates from close-in exoplanets suggesting that the atmospheric depth can be substantially smaller than that on the Earth. In a scenario with the atmospheric thickness of 1/10 of Earth's, the radiation dose from close-in planets including Proxima Centauri b and TRAPPIST-1 e reach near fatal dose levels with annual frequency of flare occurrence from their hoststars. △ Less

Submitted 18 June, 2019; v1 submitted 16 June, 2019; originally announced June 2019.

Comments: 37 pages, 19 figures, 4 tables. Accepted for publication in The Astrophysical Journal (on June 16, 2019), Version 2 (fixed typo)

ALMA unveils widespread molecular gas clumps in the ram pressure stripped tail of the Norma jellyfish galaxy

Authors: Pavel Jachym, Jeffrey D. P. Kenney, Ming Sun, Francoise Combes, Luca Cortese, Tom C. Scott, Suresh Sivanandam, Elias Brinks, Elke Roediger, Jan Palous, Michele Fumagalli

Abstract: We present the first high-resolution map of the cold molecular gas distribution, as traced by CO(2-1) emission with ALMA, in a prominent ram pressure stripped tail. The Norma cluster galaxy ESO 137-001 is undergoing a strong interaction with the surrounding intra-cluster medium and is one of the nearest jellyfish galaxies with a long multi-phase tail. We have mapped the full extent of the tail at… ▽ More We present the first high-resolution map of the cold molecular gas distribution, as traced by CO(2-1) emission with ALMA, in a prominent ram pressure stripped tail. The Norma cluster galaxy ESO 137-001 is undergoing a strong interaction with the surrounding intra-cluster medium and is one of the nearest jellyfish galaxies with a long multi-phase tail. We have mapped the full extent of the tail at 1" (350 pc) angular resolution and found a rich distribution of mostly compact CO regions extending to nearly 60 kpc in length and 25 kpc in width. In total about 10^9 M_sun of molecular gas was detected. The CO features are found predominantly at the heads of numerous small-scale (~ 1.5 kpc) fireballs (i.e., star-forming clouds with linear streams of young stars extending toward the galaxy) but also of large-scale (~ 8 kpc) super-fireballs, and double-sided fireballs that have additional diffuse ionized gas tails extending in the direction opposite to the stellar tails. The new data help to shed light on the origin of the molecular tail - CO filaments oriented in the direction of the tail with only diffuse associated Halpha emission are likely young molecular features formed in situ, whereas other large CO features tilted with respect to the tail may have originated from the densest gas complexes that were pushed gradually away from the disk. The ALMA observations of ESO 137-001, together with observations from HST, Chandra and VLT/MUSE, offer the most complete view of a spectacular ram pressure stripped tail to date. △ Less

Submitted 30 May, 2019; originally announced May 2019.

Comments: submitted to ApJ (1. revision)

Detection of large scale Ly$α$ absorbers at large angles to the radio axis of high-redshift radio galaxies using SOAR

Authors: M. Silva, A. Humphrey, P. Lagos, R. Guimarães, T. Scott, P. Papaderos, S. G. Morais

Abstract: We present an investigation of the properties of the extended Ly$α$ halo and the large-scale \ion{H}{I} absorbing structures associated with 5 high-redshift radio galaxies at z $>$ 2, using the Goodman long-slit spectrograph on the SOAR telescope, with the slit placed at large angles ($>$45$^{\circ}$) to the radio axis, to study regions that are unlikely to be illuminated by the active nucleus. Sp… ▽ More We present an investigation of the properties of the extended Ly$α$ halo and the large-scale \ion{H}{I} absorbing structures associated with 5 high-redshift radio galaxies at z $>$ 2, using the Goodman long-slit spectrograph on the SOAR telescope, with the slit placed at large angles ($>$45$^{\circ}$) to the radio axis, to study regions that are unlikely to be illuminated by the active nucleus. Spatially extended Ly$α$ emission is detected with large line widths (FWHM = 1000 -- 2500 km s$^{-1}$), which although impacted by resonant scattering, is suggestive of turbulent motion. We find a correlation between higher blueshifts and higher FWHM, which is an indication that radial motion dominates the bulk gas dynamics perpendicular to the radio axis, although we are unable to distinguish between outflow and infall scenarios due to the resonant nature of the Ly$α$ line. Extended, blueshifted Ly$α$ absorption is detected in the direction perpendicular to the radio axis in three radio galaxies with minimum spatial extents ranging from $\gtrsim$27 kpc to $\gtrsim$35 kpc, supporting the idea that the absorbing structure covers the entire Ly$α$ halo, consistent with being part of a giant, expanding shell of gas enveloping the galaxy and its (detected) gaseous halo. △ Less

Submitted 10 September, 2018; originally announced September 2018.

Comments: 16 pages, 5 figures, 3 Tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society 2018. Published: 2018 August 24

Adapted Deep Embeddings: A Synthesis of Methods for $k$-Shot Inductive Transfer Learning

Authors: Tyler R. Scott, Karl Ridgeway, Michael C. Mozer

Abstract: The focus in machine learning has branched beyond training classifiers on a single task to investigating how previously acquired knowledge in a source domain can be leveraged to facilitate learning in a related target domain, known as inductive transfer learning. Three active lines of research have independently explored transfer learning using neural networks. In weight transfer, a model trained… ▽ More The focus in machine learning has branched beyond training classifiers on a single task to investigating how previously acquired knowledge in a source domain can be leveraged to facilitate learning in a related target domain, known as inductive transfer learning. Three active lines of research have independently explored transfer learning using neural networks. In weight transfer, a model trained on the source domain is used as an initialization point for a network to be trained on the target domain. In deep metric learning, the source domain is used to construct an embedding that captures class structure in both the source and target domains. In few-shot learning, the focus is on generalizing well in the target domain based on a limited number of labeled examples. We compare state-of-the-art methods from these three paradigms and also explore hybrid adapted-embedding methods that use limited target-domain data to fine tune embeddings constructed from source-domain data. We conduct a systematic comparison of methods in a variety of domains, varying the number of labeled instances available in the target domain ($k$), as well as the number of target-domain classes. We reach three principal conclusions: (1) Deep embeddings are far superior, compared to weight transfer, as a starting point for inter-domain transfer or model re-use (2) Our hybrid methods robustly outperform every few-shot learning and every deep metric learning method previously proposed, with a mean error reduction of 34% over state-of-the-art. (3) Among loss functions for discovering embeddings, the histogram loss (Ustinova & Lempitsky, 2016) is most robust. We hope our results will motivate a unification of research in weight transfer, deep metric learning, and few-shot learning. △ Less

Submitted 27 October, 2018; v1 submitted 22 May, 2018; originally announced May 2018.

Preparation and analysis of strain-free uranium surfaces for electron and x-ray diffraction analysis

Authors: JE Sutcliffe, JR Petherbridge, T Cartwright, R Springell, TB Scott, JE Darnbrough

Abstract: This work describes a methodology for producing high quality metallic surfaces from uranium primarily for characterisation and investigations involving electron backscatter diffraction. Electrochemical measurements have been conducted to inform ideal polishing conditions to produce surfaces free from strain, induced by mechanical polishing. A commonly used solution for the electropolishing of uran… ▽ More This work describes a methodology for producing high quality metallic surfaces from uranium primarily for characterisation and investigations involving electron backscatter diffraction. Electrochemical measurements have been conducted to inform ideal polishing conditions to produce surfaces free from strain, induced by mechanical polishing. A commonly used solution for the electropolishing of uranium, consisting in part of phosphoric acid, was used to conduct the electrochemical experiments and polishing. X-ray diffraction techniques focusing on the surface show low stresses and strains are exhibited within the material. This is mirrored in good quality electron backscatter diffraction. △ Less

Submitted 15 March, 2018; originally announced March 2018.