Astrophysics of Galaxies
Bulgeless Evolution And the Rise of Discs (BEARD) I. Physical drivers of the mass-size relation for Milky Way-like galaxies
C. Marrero-de la Rosa, J. Méndez-Abreu, A. de Lorenzo-Cáceres et al. (+20 more)
In the standard $\Lambda$ cold dark matter ($\Lambda$CDM) cosmology, the existence of massive pure-disc
galaxies remains challenging within the hierarchical framework and is key to understanding the evolutionary history of Milky Way-like systems. In this work, we investigate the physical origin of the scatter in the
stellar mass-size relation of massive spiral
galaxies, with a particular focus on bulgeless systems. We analyse 22 nearby bulgeless
galaxies from the Bulgeless
Evolution And the Rise of Discs (BEARD) survey using deep $g$- and $r$-band imaging obtained with the 2.5 m Isaac Newton
Telescope Wide Field Camera. We derive surface-brightness, colour, and
stellar-mass-density radial profiles to measure $R_1$, the radius where $\Sigma_* = 1\,\mathrm{M}_\odot\,\mathrm{pc}^{-2}$, adopted here as a physically motivated size proxy. Point spread function (PSF) effects are corrected through
star subtraction and wavelet deconvolution. BEARD bulgeless
galaxies follow the tight
stellar mass-$R_1$ relation defined in previous studies, with a similar scatter of $\sim 0.1$ dex. Using
galaxies from the IllustrisTNG50 simulation, we find that the scatter is linked to morphology, with bulgeless, BEARD-like analogues and bulge-dominated
galaxies tracing the upper and lower envelopes of the relation, respectively. This trend correlates with the specific central
stellar mass density, $\Sigma^{\mathrm{spec}}_{1,\mathrm{kpc}}$, suggesting that differences between observations and simulations reflect the broader central-density range spanned by BEARD bulgeless
galaxies. A deeper analysis of the physical driver of this morphological segregation reveals that the scatter in the mass-size relation is also related to the spatial configuration of merger events, rather than their frequency, with bulgeless systems tending to inhabit
halos with a slightly higher
spin. (abridged)
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All authors C. Marrero-de la Rosa, J. Méndez-Abreu, A. de Lorenzo-Cáceres, S. Cardona-Barrero, J. Román, E. Arjona-Gálvez, M. Chamorro-Cazorla, E.M. Corsini, L. Costantin, V. Cuomo, C. Dalla Vecchia, A. Di Cintio, D. Fernández, D. Gasparri, E. Iodice, D. Mayya, L. Morelli, F. Pinna, A. Pizzella, D. Rosa-González, Y. Rosas-Guevara, O. Vega, S. Zarattini
Astrophysics of Galaxies
Bulgeless Evolution And the Rise of Discs (BEARD) III. A numerical simulation view of satellites around Milky-Way analogues
Salvador Cardona-Barrero, Jairo Méndez-Abreu, Adriana de Lorenzo-Cáceres et al. (+17 more)
$Aims$. The existence of massive disc
galaxies with little or no bulge challenges conventional $\Lambda$ cold dark matter model, which typically favours dynamically hot central structures due to early collapse and mergers. The study of these bulgeless disc
galaxies is the aim of the Bulgeless
Evolution And the Rise of Discs (BEARD) survey, as they offer a unique opportunity to investigate the link between
galaxy morphology and the properties of their satellite systems. $Methods$. Using the high-resolution cosmological hydrodynamical simulation TNG50-1, we studied the satellite populations of 135 bulgeless
galaxies. We compared their satellite properties to those of a bulge-dominated control sample with matched
stellar masses. Our analysis focuses on satellite abundance, luminosity functions, spatial distribution, orbital
alignment, and infall histories. $Results$. We find that satellite abundance is largely independent of host
galaxy morphology. However, satellites around bulgeless
galaxies exhibit luminosity functions with a steeper faint-end slope, are more centrally concentrated, and show stronger orbital
alignment with the host disc plane. The orbital
alignment originates from coherent post-infall dynamical
evolution that depends on host
galaxy morphology. The infall of more massive satellites can additionally perturb this process, contributing to a weakening or temporary stalling of the secular
alignment. $Conclusions$. Due to the co-
evolution of the host
galaxy and the satellite system, the morphology of the central
galaxy leaves a clear imprint on its satellite system. Bulgeless
galaxies tend to have dynamically colder, more aligned, and more centrally concentrated satellite populations. These trends reflect a more quiet merger history and support the use of satellite properties as tracers of host
galaxy formation pathways.
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All authors Salvador Cardona-Barrero, Jairo Méndez-Abreu, Adriana de Lorenzo-Cáceres, Carlos Marrero de la Rosa, Yetli Rosas-Guevara, Elena Arjona-Gálvez, Mario Chamorro Cazorla, Nelvy Choque-Challapa, Enrico Maria Corsini, Arianna Di Cintio, David Fernandez, Daniele Gasparri, Divakara Mayya, Lorenzo Morelli, Francesca Pinna, Alessandro Pizzella, Javier Román, Daniel Rosa Gonzalez, Olga Vega, Stefano Zarattini
High Energy Astrophysical Phenomena
GRB 260310A/SN 2026fgk: Photometric and Spectroscopic Evolution of a Nearby GRB-Supernova and an Exceptionally Bright Afterglow at z=0.153
Brendan O'Connor, Malte Busmann, Xander J. Hall et al. (+24 more)
The association of broad-lined Type Ic
supernovae with long-duration gamma-ray bursts (GRBs) has been known for 28 years. However, only about seventy gamma-ray burst
supernovae (GRB-SNe) have been identified, of which only half have spectroscopic classifications. At $z=0.153$, GRB 260310A is the 12th spectroscopically confirmed GRB-SN discovered within 1 Gpc, offering a critical opportunity to follow one of these rare
supernovae in detail. We present optical to near-infrared imaging and spectroscopy of GRB 260310A and SN 2026fgk out to 65 d after discovery. The optical afterglow is among the brightest ever observed from a GRB. Spectra obtained more than two weeks after the explosion reveal broad absorption features that securely identify SN 2026fgk as a Type Ic-BL
supernova. Modeling of the multi-wavelength ($grizJK_s$) lightcurve shows that the
supernova is approximately half the luminosity ($k_\textrm{98bw}=0.4-0.6$) of the canonical GRB-SN 1998bw. We derive a nickel mass of $M_\textrm{Ni}=0.4-0.5$ $M_\odot$ with a total ejected mass of $M_\textrm{ej}\approx4-6 $ $M_\odot$ and kinetic energy $E_\textrm{K}=(3-8)\times10^{51}$ erg. The GRB exploded at an extremely large offset of 15 kpc from its host
galaxy. Long-slit spectra reveal a “bridge” of nebular emission extending along the
galaxy's disk to the GRB location, which has a sub-
solar metallicity ($\sim$\,$0.4Z_\odot$), compared to a near
solar metallicity for the host
galaxy. This indicates that the large offset arises from the
galaxy's extended light profile rather than an isolated environment.
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All authors Brendan O'Connor, Malte Busmann, Xander J. Hall, Kenta Taguchi, Masaomi Tanaka, Daniel Gruen, Seiji Toshikage, Ariel J. Amsellem, Ziyuan Zhu, Antonella Palmese, Dylan Green, John Banovetz, Yu-Han Yang, Eleonora Troja, Hendrik van Eerten, Julius Gassert, Mitra Maleki, Stephen Bailey, Segev BenZvi, Tomas Cabrera, Keerthi Kunnumkai, Adam D. Myers, Christoph Ries, David Schlegel, Michael Schmidt, Silona Wilke, Muskan Yadav
High Energy Astrophysical Phenomena
Flavor Conversion Enhances or Suppresses Supernova Explodability Independent of the Progenitor Mass
Mariam Gogilashvili and Irene Tamborra
Flavor conversion can affect the
neutrino-driven delayed explosion mechanism of collapsing massive
stars, altering the efficiency of shock revival. We perform core-collapse
supernova simulations in spherical
symmetry for a set of progenitors with masses of $9.75\, M_\odot$, $11\, M_\odot$, $16.5\, M_\odot$, $28\, M_\odot$, $40\, M_\odot$, and $60\, M_\odot$, accounting for a mixing-length treatment for convection.
Flavor conversion is modeled assuming instantaneous
flavor equipartition below a critical
baryon density, while conserving the
lepton number. Regardless of the progenitor compactness, its mass, or the
nuclear equation of state, we find that
flavor conversion can increase heating (cooling) and enhance (hinder) the
supernova explosion, if triggered near the gain (
neutrino decoupling) region. Our findings suggest that the interplay among the region of the
supernova core where
flavor conversion occurs, the progenitor properties, and the
nuclear equation of state is crucial in determining the fate of explosion and the properties of the compact remnant.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Affine ANEC selects the closed FRW branch for geodesically complete cosmology
Nathan L. Burwig and Damien A. Easson
We study the relation between geodesic completeness, the averaged null energy condition (ANEC), and spatial
curvature in Friedmann–Robertson–Walker (FRW) cosmology within classical general relativity. Using the affinely parameterized ANEC along radial null geodesics, we prove that non-static flat or open FRW spacetimes in the regular classes considered here cannot be both null geodesically complete and ANEC-satisfying. Bounded oscillatory or cyclic flat/open models do not circumvent the obstruction: the negative affine-ANEC bulk term accumulates over infinitely many cycles, giving \(I_{\rm ANEC}=-\infty\) for non-static periodic cases. Equivalently, within these classes, non-static ANEC-satisfying flat or open models are null incomplete. The sign obstruction is absent in closed \((k=+1)\) FRW geometry, where the positive
curvature term enters the affine ANEC identity with the opposite sign and can support nonsingular, geodesically complete cosmologies with ordinary NEC-respecting matter. We give explicit closed-FRW scalar-field constructions, including a fully analytic quadratic reconstruction and a cubic-root reconstruction in closed quadrature, and contrast them with their flat realizations, which require NEC-violating support. Furthermore, we quantify how positive
curvature can bias flat-model reconstructions toward an effective phantom equation of state, finding only a percent-level effect under current
curvature bounds. The result is a
curvature classification of ANEC-compatible eternal FRW cosmology: flat and open branches are obstructed, while the closed branch admits explicit complete realizations, with global de Sitter appearing as the
vacuum limiting representative.
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Astrophysics of Galaxies
Environmental Sculpting of Galaxy Structure at Fixed Stellar Mass: A Multi-Scale Analysis Across Cosmic Time using 3 Million HSC Galaxies
Caitlin Igel, Aritra Ghosh, Andrew J. Connolly et al. (+4 more)
The extent to which
galaxy structure is shaped by environment beyond the local universe, once
stellar mass is controlled, remains an open question in
galaxy evolution. We address this challenge using an unprecedentedly large sample of $\sim$3 million
galaxies from the Hyper Suprime-Cam Subaru Strategic Program spanning $0.3 \leq z < 0.7$ with $\log(M/M_{\odot}) \geq 8.9$. We correlate a mass-independent bulge-to-total ratio statistic with large-scale overdensity maps and cluster catalogs, propagating structural parameter posteriors through a Monte Carlo framework to robustly assess significance. We confirm with $>5\sigma$ confidence that
galaxy structure depends on environment at fixed
stellar mass, but this dependence is secondary to
stellar mass and varies with
redshift, mass, and environmental scale. At $z < 0.5$, we detect no significant structural correlation with large-scale overdensity, but cluster
galaxies show statistically significant bulge enhancement compared to mass-matched field
galaxies, indicating cluster-specific processes such as ram-pressure stripping and cumulative
tidal interactions dominate structural transformation at these epochs. At $z \geq 0.5$, massive
galaxies exhibit bulge-enhancement across both cluster- and large-scale environments, while lower-mass systems show enhancement only in cluster environments. This indicates that environmental mechanisms operate across broader spatial scales at earlier
cosmic epochs, and enhanced merger rates, group preprocessing, and
cosmic web stripping augment cluster-specific processes. By separating into
star-forming and quiescent subsamples, we find nearly flat trends within each, demonstrating that the observed environmental effects arise from coupled morphological and
star formation transformations. These results collectively reveal the multi-scale, epoch-dependent nature of environmental effects on
galaxy structure.
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All authors Caitlin Igel, Aritra Ghosh, Andrew J. Connolly, Brant Robertson, C. Megan Urry, Louise O. V. Edwards, Rhythm Shimakawa
High Energy Astrophysical Phenomena
Low-Luminosity Type IIP Supernovae from the Zwicky Transient Facility Census of the Local Universe. III: Hunting for electron-capture supernovae using nebular spectroscopy
Kaustav K. Das, Anders Jerkstrand, Mansi M. Kasliwal et al. (+18 more)
Electron-capture
supernovae (ECSNe) may arise from ONeMg-core collapse in super-asymptotic
giant branch (sAGB)
stars near the low-mass core-collapse limit ($\approx\!8$–$10$\,\Msun). At early times, models predict that ECSNe resemble low-mass red supergiant iron-core-collapse SNe (FeCCSNe), making the two channels difficult to distinguish. Nebular spectroscopy, however, can reveal differences in ejecta composition. We present a systematic sample of nebular spectra of 19 low-luminosity Type IIP (LLIIP) SNe from the ZTF CLU survey, obtained 115$-$450\,d after explosion. Their low velocities expose narrow lines blended in brighter SNe, which we identify and model to constrain progenitor properties. We find a strong correlation between the FWHM of H\,i\,$\lambda$6563 and peak luminosity, showing that LLIIP SNe occupy the low-energy end of the core-collapse population, but no correlation with plateau duration, suggesting that envelope and core properties are not tightly linked. Only one SN reaches the extremely low H\,i\,$\lambda$6563 widths predicted for the weakest $\sim$9\,M$_\odot$ explosion models, implying that such low-energy events are intrinsically rare. Combining our sample with 118 literature nebular spectra of Type II SNe, we infer an IMF slope of $2.1\pm1.2$. We also introduce an `ECSN score” based on the absence of He- and O-shell emission lines, and identify two plausible ECSN candidates, SN~2023bvj and SN~2024btj. However, neither shows the extremely narrow nebular lines predicted by current ECSN models. If ECSNe arise predominantly through the LLIIP channel, we infer an upper limit on the ECSN rate of $\lesssim (5$–$8)\times10^{2}\,\mathrm{Gpc^{-3}\,yr^{-1}}$, corresponding to a narrow sAGB progenitor mass window of $\Delta M_{\rm sAGB} \lesssim 0.02$–$0.06\,\mathrm{M_\odot}$.
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All authors Kaustav K. Das, Anders Jerkstrand, Mansi M. Kasliwal, Jesper Sollerman, Christoffer Fremling, Steve Schulze, Avishay Gal-Yam, Tomas Ahumada, Shreya Anand, Bart van Baal, Michael W. Coughlin, Sofia Covarrubias, Richard Dekany, Nicholas Earley, W. V. Jacobson-Galán, Joahan Castaneda Jaimes, Frank J. Masci, Yu-Jing Qin, Reed Riddle, Sam Rose, Yashvi Sharma
Instrumentation and Methods for Astrophysics
Hyrax: An Extensible Framework for Rapid ML Experimentation and Unsupervised Discovery in the Era of Rubin, Roman, and Euclid
Aritra Ghosh, Drew Oldag, Michael Tauraso et al. (+29 more)
The NSF-DOE Vera C. Rubin Observatory, Roman Space
Telescope, Euclid, and other next-generation surveys will deliver imaging, spectroscopic, and time-domain data at scales that increasingly shift the bottleneck in astronomical machine learning (ML) projects from model design to infrastructure. We present Hyrax, an open-source, modular, GPU-enabled Python framework that supports the full ML lifecycle in astronomy: from data acquisition and training to inference and experiment comparison, with capabilities including
multimodal dataset support, integrated vector databases for similarity search, and interactive two- and three-dimensional latent-space exploration for unsupervised discovery. We demonstrate Hyrax's versatility through five representative applications on real survey data: (i) unsupervised representation learning on $\sim 4\times10^5$ Rubin Legacy Survey of Space and Time (LSST) Data Preview 1 (DP1)
galaxies, surfacing new merger and low-surface-brightness candidates missing from reference Euclid and Dark Energy Survey catalogs, while also isolating imaging artifacts – all without labeled training data; (ii) hybrid density-based clustering for identifying cluster-scale gravitational lens candidates in DP1 data; (iii)
multimodal early-time transient classification in the Zwicky Transient Facility leveraging light curves, spectra, images, and metadata; (iv) supervised false-positive filtering in shift-and-stack searches for distant
solar system objects in the Dark Energy Camera Ecliptic Exploration Project survey; and (v) supervised detection of semi-resolved
dwarf galaxies in Hyper Suprime-Cam and LSST-like imaging using synthetic source injection. Together, these results demonstrate that Hyrax provides astronomy-specific ML infrastructure that enables systematic discovery and rapid methodological iteration across next-generation astronomical surveys.
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All authors Aritra Ghosh, Drew Oldag, Michael Tauraso, Andrew J. Connolly, Peter Ferguson, Derek Jones, Gourav Khullar, Argyro Sasli, Samarth Venkatesh, Gracia Wang, Maxine West, Dylan Berry, Neven Caplar, Colin Orion Chandler, Tanawan Chatchadanoraset, Michael W. Coughlin, Melissa DeLucchi, Alexandra Junell, Diego Miura, Felipe Fontinele Nunes, Wilson Beebe, Doug Branton, Sandro Campos, Liam Cunningham, Mi Dai, Jeremy Kubica, Konstantin Malanchev, Rachel Mandelbaum, Sean McGuire, Imad Pasha, Dan S. Taranu, Tianqing Zhang
High Energy Astrophysical Phenomena
Directly tracking the re-brightening of a supermassive black hole accretion disk
R. Middei, E. Nardini, C. Done et al. (+12 more)
Accretion onto supermassive black holes powers the most luminous persistent sources in the Universe, the so-called active
galactic nuclei, whose emission is characterized by two distinct spectral components: thermal optical/ultraviolet radiation from an optically thick
accretion disk and a power-law X-ray tail from a corona located in the innermost regions of the
accretion flow. Yet, how radiatively efficient
accretion disks develop and couple to the hot corona remains poorly understood. Using six years of simultaneous ultraviolet and X-ray monitoring of the nearby active
galaxy ESO 511-G030, we witness a dramatic
evolution of the broadband spectral energy distribution, driven by an increase of the ultraviolet flux from the disk by more than an order of magnitude over a time scale of less than three years. The overall behavior is unlikely to track an uncovering event, and is instead compatible with a progressive recovery of the optically thick component of the
accretion flow. At
accretion rates higher than approximately one per cent of the Eddington limit, ultraviolet and X-ray data are tightly coupled and follow the well-defined, non-linear correlation between disk and corona found in the more luminous
quasars. Below this threshold, the relation apparently breaks down, as expected in case of evaporation of the inner
accretion disk into a geometrically thick, optically thin hot flow. This is a strong hint of an
accretion-state transition analogous to those observed in
stellar-mass black holes, and confirms the need for a paradigm change in the models of radiatively efficient
accretion flows around supermassive black holes.
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All authors R. Middei, E. Nardini, C. Done, E. Lusso, F. Vagnetti, G. Risaliti, E. Piconcelli, S. Bianchi, G. Matzeu, A. Trindade Falcão, D. Ł. Król, M. Perri, A. Maselli, K. Horne, J. V. Hernández Santisteban
High Energy Astrophysical Phenomena
Automating the detection of polarization angle rotations in blazars. Re-analysis of RoboPol data reveals 27 new rotations
Anastasia Glykopoulou, Ioannis Liodakis and Dmitry Blinov
We present an automated pipeline for the detection of EVPA rotations in blazars, integrating correction of the 180$^\circ$ ambiguity,
Bayesian Blocks
segmentation, and statistical validation. Applied to RoboPol monitoring data, the method identified 48 rotations across 25 sources, including multiple events in RBPLJ2232+1143, RBPLJ1751+0939, RBPLJ1800+7828, and RBPLJ2253+1608. The rotations span amplitudes from 90.8$^\circ$ to 359.7$^\circ$, durations between 7.0 and 111.3 days, and rotation rates averaging 5.0$^\circ$/day. Comparison with previous catalogs reveals systematic differences:
Bayesian Blocks rotations are on average $\sim$10% larger in amplitude, about twice as long in duration, and roughly two-thirds slower in angular velocity, reflecting systematic biases between adaptive binning and manual
segmentation. In addition, we report 27 previously unreported rotations, including 11 from the final 2016–2017 season. A correlation analysis with contemporaneous
Fermi–LAT $\gamma$-ray light curves shows that longer rotations tend to coincide with enhanced $\gamma$-ray activity, while rotation amplitude alone is not predictive of $\gamma$-ray brightness. Our pipeline minimizes subjective biases, expands the list of known EVPA rotations, and provides a reproducible framework for future multiwavelength studies of blazar jet dynamics and particle acceleration.
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Solar and Stellar Astrophysics
Astrometric exoplanet detection survives solar-like stellar contamination
Conaire Deagan, Benjamin T. Montet, P. Tuthill et al. (+3 more)
Astrometric monitoring of
stars provides a promising method for discovery of low-mass
planets around nearby Sun-like
stars. The astronomical community has proposed several
telescopes designed to perform high-precision astrometric observations. One limiting factor intrinsic to
stars is the astrometric noise - or "jitter" - induced by surface
stellar activity such as starspots and faculae. Despite previous estimates, the relative size of this signal has not been empirically measured from direct photometric observations. We analyse high-resolution images of the Sun to quantify the photometric centroid jitter across three narrow wavelength regions over nearly a decade, spanning high and low activity periods of the
Solar cycle. We compare our findings to previous theoretical estimates. We scale this jitter to simulate how a
Solar-twin would appear at various distances, establishing an astrometric noise floor below which detection is significantly complicated by
stellar activity. We also introduce starspot simulations that augment our data. We find the typical astrometric jitter of the Sun at \(\lambda = 607.2 \pm 0.25\text{nm}\) to be \(0.342\mu \text{as pc}\), ranging between \(0.058\mu \text{as pc}\) and \(1.294\mu \text{as pc}\) for low and high activity periods, respectively. This is lower than the expected \(\approx 3\mu \text{as}\) astrometric signal that an Earth-like
planet would produce around a Sun-like
star, at 1 pc. Therefore, the astrometric noise floor imposed by intrinsic
stellar activity sets a detection limit below one Earth but greater than Mars around
Solar-analog
stars, making instrument precision the limiting factor for Earth-like
exoplanet searches.
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All authors Conaire Deagan, Benjamin T. Montet, P. Tuthill, M. Ferraro, R. Lyu, E. Sheehan
High Energy Astrophysical Phenomena
Mapping 3-D Explosive Nucleosynthesis in Type II Supernova 2024ggi with Infrared Emission Lines
W. V. Jacobson-Galán, L. Dessart and D. Vartanyan
We present analysis and modeling of optical and infrared (IR) spectroscopy of the Type II
supernova (SN II) 2024ggi obtained with ground-based instruments and the James Webb Space
Telescope (JWST) at phases of ~265 - 400 days. The near- and mid-IR spectra reveal diverse iron-group emission-line morphologies, including double-peaked profiles in [Ni I] 3.119 and 11.998 $\mu$m, [Fe II] 1.644 and 17.931 $\mu$m, and [Co I] 12.255 $\mu$m, alongside Gaussian profiles in [Ni II] 1.939 $\mu$m, [Co II] 10.520 $\mu$m, and [Ni I] 7.505 and 11.304 $\mu$m. These differences imply both chemical inhomogeneity and aspherical ionization of inner ejecta, consistent with expectations from the $^{56}$Ni bubble effect. Modeling of double-peaked profiles supports an ejecta distribution with polar enhancements as large as ~7 for Ni/Co/Fe-rich material and ~2 for intermediate-mass elements. LTE estimates imply a stable Ni mass of $M_{\rm Ni}\approx1.3\times10^{-3}$ M$_{\odot}$, but electron densities near critical values indicate departures from LTE. Comparisons to non-LTE radiative transfer models favor a progenitor mass of ~12 - 15.2 M$_{\odot}$. We show that a simple mapping between elemental mass distribution and projected velocity reproduces line profiles produced in a CMFGEN radiative transfer calculation. We apply this property to 3-D
neutrino-driven explosion simulations and predict Ni emission profiles for varying viewing angles. We find that only energetic 3-D explosion models of high-mass progenitors reproduce the observed extent of Ni mixing in SN 2024ggi, conflicting with progenitor masses inferred from radiative transfer models. These results demonstrate the utility of resolved nebular IR lines as direct probes of the 3-D distribution of explosively synthesized material in core-collapse SNe.
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Earth and Planetary Astrophysics
Planetary formation tracks on the Hertzsprung-Russell diagram: Visualising the processes of giant planet growth
Benedikt Gottstein, Gabriel-Dominique Marleau and Christoph Mordasini
The Hertzsprung-Russell diagram (HRD) is central to
stellar astrophysics but has rarely been used to interpret
planet formation. We extend the HRD concept to forming
planets and study how solid and gas
accretion, cooling/contraction, and migration shape luminosity-temperature tracks in different formation scenarios. We compute planetary interior structures throughout formation and
evolution with the Bern model and, for the first time, couple it to radiation-hydrodynamical simulations to obtain a time-dependent
accretion-shock heating efficiency, helping to address the cold-/hot-start ambiguity. Planetary HRDs exhibit three branches corresponding to successive phases: (i) an ascending branch during solid-dominated growth, strongly set by the size of accreted bodies (and thus the solid
accretion rate) and by migration; for in-situ planetesimal
accretion we find analytically $L \propto T^8$. (ii) A near-horizontal branch beginning at detachment when gas
accretion becomes disk-limited and contraction accelerates; hot
accretion, higher masses, and pebble
accretion bend tracks upward. Increasing electron degeneracy after detachment lowers interior temperatures and stabilises radii. (iii) A descending branch where
accretion ends and
planets join constant-mass cooling tracks with weak radius
evolution and $L \sim T^4$. Our tracks agree well with synthetic populations and are broadly consistent with directly imaged
planets. Populating the short-lived early branches observationally will be difficult, and embedded accreting
planets require models including
accretion-shock emission and circumplanetary-disk reprocessing.
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Earth and Planetary Astrophysics
Mars as an Exoplanet: Lessons from a Planet at the Edge of Habitability
Stephen R. Kane, Paul K. Byrne, Skylar D'Angiolillo et al. (+5 more)
Mars is the
Solar System's canonical small, rocky
planet that transitioned from early geologic activity and surface
liquid water to a cold and arid
planet with a thin, cold, CO$_2$-dominated atmosphere. The
evolution of Mars, in the context of such planetary parameters as size, mass, atmosphere, insolation flux, magnetosphere, and impact history, harbor important diagnostics regarding the development and sustainability of habitable surface conditions. In this work, we synthesize how the study of Mars contributes to our understanding of
exoplanet processes, such as volatile delivery and loss, photochemistry,
climate evolution (including CO$_2$ condensation and atmospheric loss), obliquity forcing, planetary architecture, and the role of intrinsic magnetism. We also evaluate optimal methods and prospects for detecting and characterizing potential Mars analogs beyond the
Solar System. We focus on relevant results from planetary missions (e.g., Mars Reconnaissance Orbiter, MAVEN, Mars Science Laboratory, Mars2020) and observational studies of
exoplanet atmospheres with the James Webb Space
telescope (JWST) and future facilities. Through the convergence of these parallel pathways of inquiry, we describe the primary science questions and suggested avenues for characterizing small rocky
planets that lie at the edge of potentially habitable conditions.
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All authors Stephen R. Kane, Paul K. Byrne, Skylar D'Angiolillo, Michelle L. Hill, Emma L. Miles, David A. Brain, Shannon M. Curry, Joana R.C. Voigt
Astrophysics of Galaxies
Bulgeless Evolution And the Rise of Discs (BEARD) II. The role of mergers in shaping the Milky Way analogues in TNG50
Yetli Rosas-Guevara, Jairo Méndez-Abreu, Adriana de Lorenzo-Cáceres et al. (+20 more)
We study the formation and
evolution of bulgeless
galaxies within the Milky Way-Andromeda analogue sample of the TNG50 simulation. Through kinematic decomposition with Mordor, we identified bulgeless
galaxies with a bulge-to-disc mass ratio of B/D<0.08, in line with the Bulgeless
Evolution And the Rise of Discs (BEARD) survey and Milky Way constraints. We compared them to bulge-dominated
galaxies (B/D>1). We find that 74% of bulgeless
galaxies experience at least one major merger (
stellar mass ratio 1:4) over their lifetime. Bulgeless
galaxies form later ($z_{50}\sim 0.7$) than bulge-dominated counterparts ($z_{50}\sim1.2$). Bulgeless
galaxies have lower-mass
haloes and higher specific
stellar angular momentum, compatible with Milky Way observations. However, specific
star formation rates and hydrogen gas fractions are slightly higher than Milky Way observations. Our analysis of the
redshift evolution of
stellar components reveals that bulgeless
galaxies have gradual disc growth with high thin disc-to-total mass ratios (D/T>0.5) since $z\sim 1$ and minimal bulge growth (B/T<0.1) since $z\sim1.5$. In contrast, bulge-dominated
galaxies have earlier disc formation, which is disrupted, resulting in higher morphology
evolution. Bulgeless
galaxies are more likely to undergo gas-rich, coplanar, and corotating mergers, promoting disc survival, compared to bulge-dominated
galaxies that encounter a broader spectrum of mergers. We also observed differences in
galaxy structure between bulgeless and bulge-dominated
galaxies without major mergers, suggesting the relevance of early gas
accretion and
alignment. Bulgeless
galaxies have younger
stellar populations and more extended
star formation histories than bulge-dominated
galaxies, which rapidly quench and have older
stellar populations. These findings elucidate the distinct merger-driven and secular pathways that give rise to Milky Way
galaxies.
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All authors Yetli Rosas-Guevara, Jairo Méndez-Abreu, Adriana de Lorenzo-Cáceres, Salvador Cardona-Barrero, Elena Arjona-Gálvez, Mario Chamorro Cazorla, Enrico Maria Corsini, Luca Costantin, Virginia Cuomo, Arianna Di Cintio, David Fernández, Daniele Gasparri, Carlos Marrero-de la Rosa, Divakara Mayya, Lorenzo Morelli, Casiana Muñoz-Tuñón, Francesca Pinna, Alessandro Pizzella, Javier Román, Daniel Rosa Gonzalez, Rubén Sanchez-Janssen, Olga Vega, Stefano Zarattini
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Quasinormal modes of Proca and Maxwell fields in $d$-dimensional Schwarzschild-AdS black holes
David C. Lopes, Tiago V. Fernandes and José P. S. Lemos
Proca and Maxwell fields in $d$-dimensional Schwarzschild black holes with anti-de Sitter (AdS) asymptotics are investigated through their linear perturbations and associated quasinormal modes (QNMs) with Dirichlet boundary conditions at infinity. The Proca field equations reduce to one decoupled and two coupled radial wave-like equations. We demonstrate how the Maxwell equations emerge from the zero-mass limit of the Proca system. Several analytical properties of the corresponding QNM spectrum are examined. To compute the QNM frequencies, we employ two complementary numerical methods particularly suited to asymptotically AdS spacetimes. Using these techniques, we determine the QNMs modes of Proca field perturbations in $4$, $5$, $6$, and $7$-dimensional Schwarzschild-AdS backgrounds. As a new result, we find numerically that scalar-type Maxwell perturbations in large $d\geq 5$ Schwarzschild-AdS black holes exhibit purely imaginary low-frequency modes, analogous to those found in vector-type gravitational perturbations. The presence of such modes is especially relevant within the AdS/CFT correspondence, as they correspond to the linearized hydrodynamic regime in the dual conformal field theory. We also analyze the influence of the Proca mass on the QNM spectrum, also emphasizing how Maxwell modes are recovered in the massless limit. The dependence of the spectrum on the black hole radius is explored. In addition, analytic expressions for the QNM frequencies of vector-type and monopole Proca perturbations, as well as Maxwell modes, are derived for small $d$-dimensional Schwarzschild-AdS black holes by matching asymptotic expansions using an intermediate region. These analytic results show good agreement with the numerical findings, confirming, in particular, the existence of purely imaginary low-frequency scalar-type Maxwell modes in large $d\geq 5$ Schwarzschild-AdS spacetimes.
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High Energy Astrophysical Phenomena · Cross-listed from physics.plasm-ph
Magnetic Prandtl number dependence of plasmoid-mediated reconnection
Vinay Kumar and Axel Brandenburg
We investigate the dependence of the plasmoid-mediated
magnetic reconnection rate on the
magnetic Prandtl number using two-dimensional magnetohydrodynamic simulations of two coalescing
magnetic islands. For Lundquist numbers below the onset of the plasmoid instability, the reconnection rate follows the expected Sweet-Parker scaling and decreases with increasing
magnetic Prandtl number. However, once the current sheet becomes plasmoid unstable, the dependence on the
magnetic Prandtl number weakens considerably. In the fully plasmoid-mediated regime, we find reconnection rates that remain nearly independent of the
magnetic Prandtl number over the explored parameter range. We show that the largest reconnection rates are associated with strongly non-linear phases involving plasmoid interactions and mergers. We further compare our results with simulations of the boundary-driven Taylor problem, where previous studies reported a stronger
magnetic Prandtl number dependence, and provide a possible explanation for the differing scalings obtained in the two setups. These results may have implications for reconnection-mediated decay in magnetically dominated
turbulence and related astrophysical systems.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
The Majoron Cosmological Window: Dark Matter and Thermal Leptogenesis
Arturo de Giorgi, Daniel Naredo-Tuero and Xavier Ponce Díaz
The majoron is the Nambu-Goldstone
boson associated with the spontaneous breaking of a global $B-L$
symmetry. Remarkably, the minimal majoron framework can simultaneously address three key empirical indications of physics beyond the Standard Model:
neutrino masses, the matter-antimatter asymmetry, and dark matter. In this work, we identify the cosmologically viable region in which majoron dark matter and high-scale thermal leptogenesis can be realised simultaneously. We show that successful leptogenesis plays a central role in making this scenario predictive: by constraining the right-handed-
neutrino mass scale, it determines the irreducible freeze-in contribution to the majoron abundance and fixes the size of the couplings relevant for visible dark matter decays. Combining the irreducible dark matter production mechanisms with warm dark matter limits and indirect searches for decaying dark matter, we map the resulting majoron cosmological window and show that future X- and gamma-ray
telescopes can probe part of the surviving parameter space.
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Cosmology and Nongalactic Astrophysics
The pre-infall bias of subhalos
M. Sten Delos and Andrew Benson
Dark matter
halos destined to fall into a more massive host differ from typical field
halos of the same mass even before infall. In cosmological simulations, we find that the progenitor mass functions of these "future subhalos" are systematically shifted toward higher masses, with the shift growing as infall approaches. The bias takes a compact form within extended Press-Schechter theory: the collapse barrier is multiplied by a function $\beta(D/D_\mathrm{infall},a)$, where $D$ is the linear growth factor at scale factor $a$ and $D_\mathrm{infall}$ is the growth factor at infall. We find $\beta(x,a)=(1-x)^{1.20+0.14a}$ for the $M_{200\mathrm{c}}$ mass definition and $(1-x)^{1.20+0.05a}$ for $M_{200\mathrm{m}}$; the explicit scale-factor dependence captures the late-time influence of dark energy. One consequence is that
halos shortly before infall are 10-15% more centrally concentrated than typical field
halos of the same mass.
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Cosmology and Nongalactic Astrophysics
The Lumina Project: CMB Optical Depth Fluctuations from Patchy Reionization
Aaron Smith, Oliver Zier, Rahul Kannan et al. (+8 more)
Patchy reionization couples the ionized-bubble morphology to the underlying density field, making the CMB Thomson optical depth sensitive to both the global ionization history and anisotropic fluctuations on the sky. Using the large-volume radiation-hydrodynamical Lumina simulation, we compute $\tau_{\rm CMB}$ in two ways: (i) from global volume- and mass-weighted ionization histories, and (ii) from explicit line-of-sight integrations through on-the-fly light cones. We find that the sightline-averaged optical depth in the light cone, $\langle \tau_{\rm LOS} \rangle = 0.0550$, exceeds the value inferred from a global volume-weighted history, $\tau_{{\rm CMB},V} = 0.0515$, by $\approx 7\%$. This enhancement is largely captured by the global mass-weighted prediction, $\tau_{{\rm CMB},m} = 0.0544$, indicating that precision comparisons to CMB optical-depth constraints should use mass-weighted electron fractions or explicit light-cone integration rather than volume-weighted ionized fractions alone. The excess optical depth accumulates primarily near $z_{\rm LOS} = 8.0^{+1.9}_{-1.3}$, where the combination of high physical density and strong ionization-field patchiness is greatest. The resulting $\tau_{\rm LOS}$ field is non-Gaussian and exhibits $\gtrsim 5\%$ sightline-to-sightline scatter, with fluctuations tracing rare early-ionized overdensities and large-scale structure. Coarse-graining experiments show that smoothing the ionization field on $\gtrsim 3 {\rm cMpc}$ scales suppresses the density-ionization correlation and biases $\tau_{\rm CMB}$ low relative to the resolved calculation. Finally, angular power spectra and real-space correlation functions decomposed into HII, HeII, and HeIII auto- and cross-contributions reveal scale-dependent departures from simple hydrogen-helium co-tracing and evolving characteristic scales with
redshift.
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All authors Aaron Smith, Oliver Zier, Rahul Kannan, Xuejian Shen, Rongrong Liu, Mark Vogelsberger, Volker Springel, Ruediger Pakmor, Sonja M. Koehler, Lars Hernquist, Meredith Neyer
Cosmology and Nongalactic Astrophysics
First detection of the moving lens effect with ACT and DESI LS
Selim C. Hotinli, Kendrick M. Smith, Simone Ferraro et al. (+4 more)
The moving lens effect is a secondary CMB anisotropy induced by the transverse motion of gravitational potentials. We develop a
Fourier-space cross-spectrum
estimator that retains the scale dependence of the signal, and apply it to the Atacama Cosmology
Telescope (ACT) DR6 CMB temperature maps and luminous red
galaxies from the DESI Legacy Imaging Surveys. Using the foreground-reduced ACT NILC map, we find strong evidence for a non-zero amplitude of the cross-correlation $b_{\rm ML} = 1.24 \pm 0.26$ ($4.8\sigma$) for the extended sample and $0.93 \pm 0.25$ ($3.7\sigma$) for the main sample, both consistent with the
halo-model prediction for the moving lens signal. Our
Fourier-based pipeline enforces separation of scales between the reconstructed velocities and the cross-correlation, which we show is essential for foreground mitigation. The residual foreground contamination is expected to be significantly smaller than the signal from both simulations and the multi-frequency analysis presented in this paper. No curl-mode test exceeds $2\sigma$, and the results are robust across analysis variants. They constitute the first detection of the moving lens effect and unlock access to transverse velocities, a new cosmological probe. When combined with the kinematic Sunyaev-Zel'dovich effect, this provides a path toward mapping the three-dimensional velocity field of the Universe, opening a new avenue for probing the growth of structure and
gravity on large scales.
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All authors Selim C. Hotinli, Kendrick M. Smith, Simone Ferraro, Ali Beheshti, Arthur Kosowsky, Elena Pierpaoli, Emmanuel Schaan
Instrumentation and Methods for Astrophysics · Cross-listed from cs.IR
Traditional statistical representations outperform generative AI in identifying expert peer reviewers
Vicente Amado Olivo, Tereza Jerabkova, Jakub Klencki et al. (+5 more)
The exponential growth of scientific submissions has strained the peer review system. Despite the rapidly expanding global pool of researchers, this unprecedented scale has rendered the previous approach of manual expert identification unfeasible. Therefore, institutions have naturally turned to Large
Language Models (LLMs) to automate intricate processes like expert reviewer identification. However, the reliability of these new models in accurately identifying domain experts lacks rigorous evaluation. We conduct a comprehensive empirical evaluation of statistical and AI-driven expertise identification methodologies to
benchmark their reliability and limitations. Framing expert identification as an information
retrieval problem, we utilize the distributed peer review system of a major international astronomical observatory, where proposal authorship serves as our proxy ground truth for domain expertise. Evaluating six
retrieval methodologies utilized across observatories and computer science conferences, we demonstrate that traditional statistical representations outperform generative AI. Specifically, Term Frequency-Inverse Document Frequency successfully identified a labeled expert within the top 25 recommendations 79.5% of the time, compared to 51.5% for GPT-4o mini. Our results highlight that distinguishing subfield expertise requires fine-grained vocabulary, which is obscured by the semantic smoothing in generative methods. By establishing a rigorous evaluation framework for automated peer review, we demonstrate that transparent and reproducible statistical representations still outperform computationally expensive LLMs in specialized scientific tasks.
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All authors Vicente Amado Olivo, Tereza Jerabkova, Jakub Klencki, John Carpenter, Mario Malički, Ferdinando Patat, Louis-Gregory Strolger, Wolfgang Kerzendorf
High Energy Astrophysical Phenomena
A universal framework to identify eccentric binary mergers: GW200105 case study
Teagan A. Clarke, Isobel M. Romero-Shaw, Charlie Hoy et al. (+3 more)
Orbital eccentricity in gravitational-wave signals from merging compact object binaries is a powerful indicator of their formation channel. Several binary black hole mergers and a
neutron star–black hole merger have been reported to exhibit signs of eccentricity, but which events are identified and the significance of the eccentricity differs between studies. Measurements of eccentricity can change depending on the choice of prior. The choice of prior is subtle: eccentricity is commonly measured at an arbitrary reference frequency, which varies from study to study. We use the candidate eccentric
neutron star–black hole merger GW200105_162426 as a case study, employing a range of priors and reference frequencies, and find the results to be strongly prior-driven. We show that the varied results reported across different studies can be partially reconciled by accounting for the
evolution of eccentricity with reference frequency. In order to make conclusive statements about eccentricity, we propose a detection statistic that does not depend on reference frequency, and which marginalises over astrophysically-motivated distributions in eccentricity. Using this detection statistic, we find reduced support for the eccentric hypothesis for GW200105_162426: we obtain a natural log Bayes factor ln B $\leq$ 0.9 comparing the eccentric, aligned-
spin hypothesis to the quasi-circular, precessing hypothesis. Our results cast doubt on the eccentric interpretation of GW200105_162426 and underscore the importance of modelling the astrophysical distributions of eccentricity in nature.
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All authors Teagan A. Clarke, Isobel M. Romero-Shaw, Charlie Hoy, Jakob Stegmann, Paul D. Lasky, Eric Thrane
High Energy Astrophysical Phenomena
Pulse profile modelling of the 2024 outburst of the accreting millisecond pulsar SRGA J144459.2-604207
Bas Dorsman, Tuomo Salmi, Anna L. Watts et al. (+14 more)
Pulse profile modelling via relativistic ray-tracing can constrain the system parameters of
neutron stars, notably their mass and radius. Among these objects, accreting millisecond
pulsars (AMPs) are promising targets, because they are bright in X-rays and their potentially polarized radiation can lead to complementary constraints on the emission geometry. We perform combined analysis of NICER and IXPE observations of the recently discovered the 448-Hz
pulsar SRGA J144459.2-604207, with IXPE providing X-ray polarization information. NICER and IXPE jointly favour a large mass and radius for our best-fitting model, for which the
neutron star has two independent hotspots. The primary hotspot is centered near the northern rotational pole, the secondary in the southern hemisphere, and the observer inclination is in the range 50-75 degrees. The primary hotspot is large (up to half the surface area) and contributes the majority of the non-pulsed X-rays, while the secondary is hotter and the major contributor to the overall pulse profile shape. However, many parameters are inferred to be near the prior bounds, which could indicate that the model does not adequately account for important physics. Furthermore, we tested several different methodologies for joint analysis of the two data sets: the results are sensitive to the method used, something that merits further study with synthetic data. In the future, we expect simultaneously recorded data will lead to improved parameter constraints, especially when multi-band and polarized data are combined.
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All authors Bas Dorsman, Tuomo Salmi, Anna L. Watts, Mason Ng, Anna Bobrikova, Alessandro Di Marco, Duncan K. Galloway, Sebastien Guillot, Mariska Hoogkamer, Yves Kini, Fabio La Monaca, Vladislav Loktev, Matteo Lucchini, Christian Malacaria, Ying-Han Mao, Alessandro Papitto, Juri Poutanen
Instrumentation and Methods for Astrophysics
WaveDriver: a Laser Guide Star AO System for HWO
Benjamin L. Gerard, Alex Geringer-Sameth, Aditya R. Sengupta et al. (+7 more)
Habitable Worlds Observatory (HWO) presents a key challenge for technology development in the coming years, requiring a $>$ $100\times$ more stable system than JWST. WaveDriver is a concept for a
laser guide
star spacecraft coupled to an adaptive optics (AO) system onboard HWO that would enable HWO to reach its picometer-level wavefront stability requirements while relaxing other HWO subsystem requirements. At LLNL and UCSC we are revisiting the concept initially proposed by Douglas et al.\ (2019). We present key results key initial results from the first phase of our project, including (1) AO control developments, including with Linear Quadratic Gaussian control and machine learning, (2) AO wavefront sensor (WFS) trade study simulations, and (3) simulations of a photonic lantern natural guide
star WFS. A key finding from our work is that WaveDriver could be needed to enable HWO's primary mirror segment stability and/or low order wavefront stability requirements.
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All authors Benjamin L. Gerard, Alex Geringer-Sameth, Aditya R. Sengupta, Alexx Perloff, Dominic F. Sanchez, Peter Waswa, Cesar Laguna, Rebecca Jensen-Clem, Lisa Poyneer, Megan Eckart
Cosmology and Nongalactic Astrophysics
Recoupled Dark Radiation reconciling CMB and DESI BAO measurements
Ravi Kumar Sharma, Maria Archidiacono and Julien Lesgourgues
Recent DESI BAO measurements, combined with CMB data, reveal a tension within the $\Lambda$CDM model that leads to a discrepancy between cosmological and laboratory bounds on the summed
neutrino mass. We show that a recoupled interacting radiation component can alleviate this cosmological tension, as well as the one with
neutrino oscillation experiments. Sterile
neutrinos interacting through a light pseudoscalar mediator provide a concrete realization of this scenario. The resulting interacting fluid modifies the CMB phenomenology, lowers the preferred matter density, and improves the consistency between CMB and DESI BAO measurements. Combining CMB with DESI DR2 BAO measurements, we find a $2.7 \sigma$ preference for a nonzero interacting sterile
neutrino component, $\nsp=0.253 \pm 0.094$, corresponding to an improvement $\Delta \chi^2=-8.98$ relative to $\Lambda$CDM. The model also reduces the tension with the SH0ES determination of the Hubble constant to the $2.4\sigma$ level.
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Instrumentation and Methods for Astrophysics
The Wide Field Imager (WFI) Instruments for the Polarimeter to Unify the Corona and Helliosphere (PUNCH)
Glenn T. Laurent, Craig E. DeForest, Matt N. Beasley et al. (+14 more)
We describe the design, hardware integration, and calibration performance of the Wide-Field Imager (WFI) instruments for the Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission. The WFI instruments are a trio of visible-light heliospheric imagers that, together, view the outer corona and
solar wind from under 3.5{\deg} to over 47{\deg} from the Sun, via sunlight that is Thomson-scattered from free electrons. In flight, the WFIs are arranged so that their collective fields of view form an approximately symmetric trefoil on the sky, comprising three circular-truncated square fields spaced 120{\deg} apart in position angle. The WFIs work with the NFI instrument, described elsewhere, to implement the full PUNCH field spanning all
solar position angles, at elongations from 1.5{\deg} to 47{\deg} from disk center. WFI is implemented using dioptric (lens) optics and deep multi-stage baffles that attenuate
solar, planetary, and lunar stray light sufficiently for ground processing to reveal the faint signal for the primary science. WFI measures both total brightness (tB) and polarized brightness (pB), via an on-board polarizing filter wheel (PFW) and charge-coupled device (CCD) camera that share a common design with those of the NFI instrument.
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All authors Glenn T. Laurent, Craig E. DeForest, Matt N. Beasley, Nicholas F. Erickson, Roy R. Graham, Mary H. Hanson, J. Marcus Hughes, Derek A. Lamb, Reith Nolan, Steve Osterman, Trent Peterson, Michael Shoffner, Kelly D. Smith, Travis Smith, Todd Veach, William L. Wells, Alexander J. Wilson
Astrophysics of Galaxies
CCD () photometry of the open cluster NGC 6793 and its dynamical evolution
Zahra Al, Yüksel Karataş, Raul Michel Murillo et al. (+4 more)
We present new astrophysical parameters for the open cluster NGC~6793 based on new CCD $UBV(RI)_{KC}$ photometry. We derived a reddening of $E(B-V) = 0.24 \pm 0.02$~mag and a heavy element abundance of $Z = 0.024$ ($[Fe/H] = +0.20$~dex). Padova isochrone fitting to the $V \times (B-V)$ colour-magnitude diagram yields an intermediate age of $525 \pm 51$~Myr and a distance modulus of $\mu = 8.80 \pm 0.05$~mag, corresponding to a distance of $d = 575 \pm 58$~pc from the Sun. The core radius of NGC~6793 appears to be shrinking due to advanced dynamical
evolution ($\log\tau_{2} = 1.13$), driven by mass segregation and the evaporation of low-mass
stars from the central region. The ratios of core to half-mass radius ($R_{c}/R_{h}$) and half-mass to Jacobi radius ($R_{h}/R_{J}$) indicate that the cluster's
evolution is governed by the combined effects of internal two-body relaxation, mass segregation, and external
tidal perturbations. The ratio $R_{t}/R_{J} = 0.99$ suggests that the cluster is currently in a tidally filling state. The parameter pairs ($t_{diss}/t_{rlx_{1}} = 40$, $\log R_{J}/R_{c} = 0.72$) and ($R_{h}/R_{J} = 0.38$, $\log\rho_{amb} = -0.88$) place NGC~6793 among the relatively compact clusters within $R_{GC} < 7.9$~kpc. This implies a compact internal structure that is stable against the combined effects of two-body encounters and
tidal heating. Given its current state, NGC~6793 will likely dissolve and disperse before entering the final contraction phase ($R_{4}$ regime).
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All authors Zahra Al, Yüksel Karataş, Raul Michel Murillo, Charles Bonatto, Orhan Güneş, İnci Akkaya Oralhan, Eyüp Kaan Ülgen
Cosmology and Nongalactic Astrophysics
Faster CMB lensing with control variates
Toshiya Namikawa and Blake D. Sherwin
We present a new method for fast computation of the realization-dependent bias, a major computational bottleneck in measurements of the
cosmic microwave background (CMB)
lensing power spectrum. The method accelerates the bias calculation by differencing two correlated estimates: one based on fully realistic masked simulations and the other on isotropic simulations, for which the bias is analytically tractable. We show that our
algorithm reduces the total computational cost of a
lensing power spectrum measurement by approximately a factor of five for Atacama Cosmology
Telescope- or Simons Observatory-like noise levels, or by a factor of three if current anisotropic filtering methods are left unchanged. Owing to its simplicity, the method can be readily implemented in existing CMB
lensing analysis pipelines.
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Instrumentation and Methods for Astrophysics · Cross-listed from stat.ME
Self-Supervised Conformal Prediction with Equivariant Bootstrapping for Image Uncertainty Quantification
Henry J. Aldridge, Tobías I. Liaudat, Marcelo Pereyra et al. (+1 more)
Inverse problems are ubiquitous in modern scientific studies and involve recovering an underlying signal from noisy observations often transformed by a measurement operator. These problems are frequently ill-posed, particularly in imaging, leading to multiple plausible solutions and considerable uncertainty in reconstructed images. In fields like the physical and biological sciences, accurate uncertainty quantification (UQ) is critical for trustworthy scientific analyses and confident diagnoses. Current UQ methods for imaging often fall short; they can be inaccurate, or require unavailable or difficult-to-acquire ground truth data for calibration, which can introduce hidden biases due to distribution shifts between calibration and observed data. We introduce a UQ approach that leverages equivariant bootstrapping to generate heuristic coverages by exploiting data
symmetries. We then refine these coverages through a conformal prediction calibration step, while crucially employing a self-supervised approach to avoid the need for ground truth calibration data. We demonstrate this method with weak
lensing mass-mapping, where we aim to reconstruct the convergence field from shear measurements of distant
galaxies weakly-lensed by gravitational fields. Mass-mapping in particular benefits from the self-supervised approach, as simulating calibration data is expensive and relies on specific cosmological models that could introduce biases in downstream cosmological inference tasks.
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All authors Henry J. Aldridge, Tobías I. Liaudat, Marcelo Pereyra, Jason D. McEwen