Astrophysics of Galaxies
From ASTRID to BRAHMA – The role of overmassive black holes in little red dots in cosmological simulations
Patrick LaChance, Aklant Kumar Bhowmick, Rupert A.C. Croft et al. (+8 more)
We investigate the origin of Little Red Dots (LRDs) using a realization of the BRAHMA cosmological hydrodynamic simulation that produces overmassive black holes at $z \sim 4\text{-}8$. We generate mock JWST observations by modeling
galaxy spectral energy distributions (including
dust attenuation) together with AGN emission using cloudy-based templates, and test whether such systems reproduce the observed LRD population. We consider both a standard low-
redshift AGN emission model and a gas-enshrouded AGN emission model, in which the AGN is embedded within unresolved dense gas that produces a strong Balmer break, and find that LRDs emerge in significantly larger numbers with the latter model. Assuming that all AGN reside in this gas-enshrouded phase, we recover LRD number densities ($\Phi \sim 2 \times 10^{-4}~\mathrm{Mpc}^{-3}$), close to the observed abundance. This implies an effective gas-enshrouded duty cycle approaching unity, which is not predicted by current theoretical models. Current JWST constraints on the high-z black hole mass function suggest that this tension may arise from a deficit of low-mass ($M_{\rm BH}\lesssim10^7~M_\odot$) LRDs in BRAHMA. Applying the same gas-enshrouded model to the ASTRID simulation, which lacks overmassive black holes, we find that the LRD abundance remains $\gtrsim2~\rm dex$ below observations. Overall, while the overmassive black holes in this BRAHMA realization substantially enhance the production of LRD-like systems, reproducing the observed LRD abundance requires them to reside in dense gas environments with unrealistically high duty cycles. We therefore conclude that overmassive black holes are unlikely to be the sole origin of the observed JWST LRD population, and may instead account for only a subset of these systems.
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All authors Patrick LaChance, Aklant Kumar Bhowmick, Rupert A.C. Croft, Tiziana Di Matteo, Yihao Zhou, Fabio Pacucci, Laura Blecha, Paul Torrey, Yueying Ni, Nianyi Chen, Simeon Bird
Cosmology and Nongalactic Astrophysics
Catalogs of optically-selected clusters and photometric luminous red galaxies from the Hyper Suprime-Cam Subaru Strategic Program final year dataset
Masamune Oguri, Yen-Ting Lin, Nobuhiro Okabe et al. (+9 more)
We construct samples of optically-selected clusters and photometric luminous red
galaxies (LRGs) from the Hyper Suprime-Cam Subaru Strategic Program final year
dataset covering $\sim 1200$~deg$^2$. The cluster catalogs extend out to the
redshift of $1.38$ and contain more than 10000 clusters with richness larger than $15$, where the richness is defined to be a membership probability weighted number of
galaxies above the
stellar masses of approximately $10^{10.2}M_\odot$. The total number of probable red cluster member
galaxies in these clusters are more than $6\times 10^5$. Photometric
redshifts of the clusters are shown to be precise with the scatter better than $\sim 0.01$ for a wide
redshift range. We detect stacked weak
lensing signals of clusters out to the
redshift of $1$, and use them to update constraints on the mass-richness relation. Our catalog of about 6 million photometric LRGs extend out to the
redshift of $1.25$, and have the scatter of the photometric
redshift better than $\sim 0.02$ for the
redshift range between $0.4$ and $1.0$.
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All authors Masamune Oguri, Yen-Ting Lin, Nobuhiro Okabe, Naomi Ota, I-Non Chiu, Momoka Fujikawa, Hung-Yu Jian, Tadayuki Kodama, Lihwai Lin, Atsushi J. Nishizawa, Rhythm Shimakawa, Yoshiki Toba
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
The Role of Microstate Degeneracy in Phase Transitions: Gravitational Waves from Bubble Entanglement
Gia Dvali and Lucy Komisel
Vacuum bubbles, formed in first order phase transitions, have important implications for cosmology. In particular, they source gravitational waves. Usually, it is assumed that, once bubbles are materialized, their state, further
evolution and mergers are well-described classically. This paper will show that this intuition breaks down for bubbles which possess high microstate degeneracy. This is generic when the phase transition breaks spontaneously a
symmetry. First, the degeneracy enhances the transition rate. Furthermore, the internal
quantum state of the bubbles profoundly affects the classical dynamics of their mergers. A bubble, no matter how macroscopic, is born in a maximally entangled
quantum state. This state can be viewed as a symmetric superposition of many different would-be classical bubbles. The inner
entanglement is largely maintained up until their mergers. The resulting true
quantum dynamics of the merger is macroscopically different from any type of classical mergers. These differences are imprinted as macroscopic features in the resulting classical gravitational waves. In this way, the inner microstate
entanglement of merging bubbles provides a qualitatively new source of gravitational waves. This phenomenon is quantified and compared with the swift
memory burden effect in black hole mergers.
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Astrophysics of Galaxies
Investigating the Reionization Epoch through 21\,cm and Line Intensity Mapping Experiments
Anirban Roy, Anthony Pullen, Patrick C. Breysse et al. (+1 more)
The epoch of reionization (EoR), marking the Universe's transition from a neutral to ionized state, represents a pivotal phase for understanding the formation of the first
stars and
galaxies. Intensity mapping of atomic and molecular lines, such as $[\mathrm{CII}]$ and CO J-ladder transitions, across a broad
redshift range is a powerful tool for investigating
star formation history,
metallicity, the distribution of gas and
dust, and the physical conditions within
galaxies. Additionally, 21\,cm line intensity mapping directly probes the neutral hydrogen content in the intergalactic medium, offering a unique window into the timing and morphology of reionization. In this study, we explore the cross-correlation between the 21\,cm signal and multi-line intensity mapping (LIM) to forecast their detectability for next-generation experiments. Our analysis emphasizes the complementary potential of these techniques to constrain parameters such as the minimum mass of ionizing sources and the ionization fraction $x_e$. Cross-correlations with LIM also enable constraints on physical properties like metal enrichment and the relationship between
star formation rates and multi-line luminosities. Using mock observations from Square Kilometre Array (SKA)-low 21\,cm and Fred Young Submillimeter
Telescope (FYST)-like LIM experiments, we find that the $[\mathrm{CII}]$–21\,cm cross-correlation can constrain reionization history by measuring $x_e$ across multiple
redshift bins with significance levels ranging from 9 to 40$\sigma$. We extend our analysis to CO transitions, showing that the CO(1-0)–21\,cm cross-correlation provides competitive constraints on reionization parameters. The synergies explored here will enable robust constraints on both reionization and LIM parameters, maximizing the scientific return of current and next-generation intensity mapping experiments.
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All authors Anirban Roy, Anthony Pullen, Patrick C. Breysse, Rachel S. Somerville
Earth and Planetary Astrophysics
Doomed Worlds II: Reassessing Suggestions of Orbital Decay for TrES-5 b
Marvin Rothmeier, Elisabeth R. Adams, Karsten Schindler et al. (+9 more)
TrES-5b is one of only three ultra-hot Jupiters (UHJs) with suggestions of a possibly decreasing orbital period that have persisted through multiple independent analyses (G. Maciejewski et al. 2021; S. R. Hagey et al. 2022; E. S. Ivshina & J. N. Winn 2022; W. Wang et al. 2024; L. C. Yeh et al. 2024). While WASP-12 b's decreasing period is well-explained by tidally induced orbital decay (K. C. Patra et al. 2017), and
stellar acceleration has been proposed for WASP-4 b (L. G. Bouma et al. 2020), the cause of the apparent trend for TrES-5 b has not been satisfactorily explained. This work extends the previous observations with 14 new ground-based transits from 2016-2024 and two newly-published midtimes for data from 2007 and 2009. Four TESS sectors (75, 77, 82, and 84) have also been included for the first time. With the new data, the case for a decreasing orbital period is much weaker than before. The revised rate of period change, dP/dt=-5.3 +/- 2.2 ms yr^-1, is less than half that was found in previous work and the preference for a quadratic over a linear model, as measured through Delta BIC_LQ, has been falling since 2020, with a current value of 11. Furthermore, these results are not robust to outliers; removing a single early transit midtime causes the effect to vanish (Delta BIC_LQ = -1). Additionally, no significant periodic signals in the transit timing data are identified. The current data are well explained by a linear ephemeris.
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All authors Marvin Rothmeier, Elisabeth R. Adams, Karsten Schindler, Andre Beck, Brian Jackson, Jeffrey P. Morgenthaler, Amanda A. Sickafoose, Malia Barker, Luigi Mancini, John Southworth, Daniel Evans, Alfred Krabbe
Astrophysics of Galaxies
Cold Gas Infall onto A Brightest Group Galaxy via A Gas-Rich Minor Merger
Ming-Yang Zhuang, Jinyi Shangguan, Yuan Bian et al. (+6 more)
Dust and cold gas are not uncommon in nearby early-type
galaxies (ETGs), and represent an important aspect of their
evolution. However, their origin has been debated for decades. Potential sources include internal processes (e.g., mass loss from evolved
stars), external mechanisms (e.g., minor mergers or cooling flows), or a combination of both. Gas-rich minor mergers have long been proposed as an important channel for cold gas fueling in both observations and simulations, but direct evidence of cold gas transportation via gas-rich minor mergers remains elusive, particularly in
galaxy groups and clusters where environmental effects are prevalent. In this letter, we present the first unambiguous case of direct cold gas transportation onto a brightest group
galaxy (BGG) at $z=0.25$, driven by an ongoing close-separation gas-rich minor merger with a mass ratio of $\sim1:56$. High-resolution JWST imaging reveals a heavily obscured, low-mass satellite that is barely visible at restframe optical wavelengths.
Tidal stripping from this satellite deposits gas and
dust onto the BGG, forming prominent $\sim$10 kpc
dust lanes in situ. Cosmological simulations indicate that such interactions preferentially occur in gas-rich satellites undergoing their first infall in highly eccentric orbits. Our results highlight the pivotal role of gas-rich minor mergers in replenishing cold gas reservoirs and shaping the
evolution of central ETGs in
galaxy groups.
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All authors Ming-Yang Zhuang, Jinyi Shangguan, Yuan Bian, Yue Shen, Luis C. Ho, Min Du, Junyao Li, Zhao-Yu Li, Jing Wang
Instrumentation and Methods for Astrophysics
Detection and characterisation of submm transient sources with a large single-dish telescope
Mike Peel, Dave Clements, Tony Mroczkowski et al. (+1 more)
The exploration of the time-variable astronomical sky at submm wavelengths is rapidly becoming more feasible with large sky surveys by
Cosmic Microwave Background
telescopes with tens of thousands of detectors. Observations with the Atacama Cosmology
Telescope and South Pole
Telescope have already detected some transients, and Simons Observatory and CCAT are expected to detect many more in the near future. Follow-up observations to characterise these transients, and surveying to uncovering fainter populations, will need high sensitivity and large fields of view at submm wavelengths, which could be provided by large single dish
telescopes such as AtLAST.
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All authors Mike Peel, Dave Clements, Tony Mroczkowski, Allen Foster
Instrumentation and Methods for Astrophysics
Atangana-Baleanu Regularized Wavelet Compression For Astronomical Time-Series
Taylan Demir and Atakan Koçyiğit
Astronomical light curves are noisy and irregular, so compression must reduce size without erasing weak transients. We propose a fractional wavelet compression method where wavelet coefficients are regularized via an Atangana Baleanu Caputo derivative with a nonsingular Mittag Leffler kernel. The induced long
memory smoothing suppresses noise while preserving coherent transits,
flares and oscillations. We give the coefficient level formulation, an efficient implementation, and comparisons with classical discrete wavelet thresholding, showing competitive compression with improved retention of low-amplitude events.
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Astrophysics of Galaxies
A wide-field, multi-line survey of CO in the Magellanic Clouds at parsec-scale resolution: characterising the molecular gas content with a 50-m single-dish submillimeter telescope
Francisca Kemper, Rosie Chen, Axel Weiss et al. (+8 more)
The Large and Small Magellanic Clouds (LMC, SMC) are nearby
dwarf galaxies whose proximity uniquely enables molecular cloud-scale resolution observations across the entire Magellanic system, a capability unmatched in any other external
galaxy. Their low
metallicities resemble conditions near the peak of
cosmic star formation, allowing resolved studies of interstellar medium (ISM) phases, molecular cloud lifecycles, and feedback processes that regulate
galaxy evolution. Comprehensive, wide-field spectroscopic mapping of CO and its isotopologues in different transitions, complemented by [CI] observations, and combined with already existing HI and HII surveys, will calibrate
star-formation laws and gas-phase partition under low-
metallicity conditions and furnish
benchmarks for interpreting high-
redshift galaxies and cosmological simulations. This science requires a large-aperture, wide-field submillimeter single dish with multi-pixel spectroscopic capabilities, operated from a high, dry site such as Chajnantor, to deliver fast, sensitive, high-resolution, degree-scale mapping with total-power fidelity. We present the case for a full molecular atlas of the Magellanic system, the enabling facility requirements, and the transformative impact on
galaxy evolution studies
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All authors Francisca Kemper, Rosie Chen, Axel Weiss, Caroline Bot, Frédéric Galliano, Suzanne Madden, Oscar Morata, Naslim Neelamkodan, Rebeca Pirvu, Monica Rubio, Kazuki Tokuda
Astrophysics of Galaxies
AtLAST – A five fold increase in the number of identified Strongly Lensed Galaxies in the sub-millimetre and its consequences
Joaquín González-Nuevo, Laura Bonavera, Juan Alberto Cano et al. (+6 more)
Strong gravitational
lensing is a powerful probe of cosmology, dark matter (DM), and high-
redshift galaxy evolution, but current samples of strongly lensed
galaxies (SLGs) remain far too small to exploit its full potential. $\textit{Herschel}$'s submillimeter (submm) surveys demonstrated that submm selection provides the most efficient and least biased route to identifying high-
redshift SLGs, yet produced only a few hundred systems over limited, heterogeneous fields. Achieving the thousands of SLGs required for precision cosmology and detailed studies of distant dusty
star-forming
galaxies demands a new, wide-area, homogeneous sub-mm survey. A facility like AtLAST, capable of extending $\textit{Herschel}$-like methodologies to much larger areas, is uniquely positioned to deliver the order-of-magnitude increase in SLG numbers needed for transformative progress.
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All authors Joaquín González-Nuevo, Laura Bonavera, Juan Alberto Cano, David Crespo, Rebeca Fernández-Fernández, Valentina Franco, Marcos M. Cueli, José Manuel Casas, Tom J. L. C. Bakx
Cosmology and Nongalactic Astrophysics
AtLAST – Determination of Halo Mass Density Profiles at kpc Scales through Magnification Bias
Joaquín González-Nuevo, Laura Bonavera, Juan Alberto Cano et al. (+9 more)
Magnification bias, the
lensing-induced modification of background source number counts, provides a uniquely powerful probe of the mass density profiles of
galaxies and clusters down to kpc scales. Unlike shear-based weak
lensing, magnification bias does not rely on
galaxy shapes and thus avoids dominant small-scale systematics. Existing studies, however, are limited by sky coverage, positional uncertainty, and insufficiently deep, confusion-limited submillimetre (submm) surveys. A next-generation wide-field, high-throughput submm facility like the proposed 50m-
telescope AtLAST is required to unlock this technique's full diagnostic power.
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All authors Joaquín González-Nuevo, Laura Bonavera, Juan Alberto Cano, David Crespo, Rebeca Fernández-Fernández, Valentina Franco, Marcos M. Cueli, José Manuel Casas, Tony Mroczkowski, Caludia Ciccone, Evanthia Hatziminaoglou, Hugo Messias
Cosmology and Nongalactic Astrophysics
AtLAST – Cosmology with submillimetre galaxies magnification bias
Laura Bonavera, Joaquin Gonzalez-Nuevo, Juan Alberto Cano et al. (+10 more)
Magnification bias offers a uniquely powerful and independent route to cosmological information. As a gravitational-
lensing observable, it probes
galaxy-matter correlations without relying on
galaxy shapes, PSF modelling, or intrinsic-
alignment corrections. Its sensitivity spans both geometry and growth: magnification bias simultaneously responds to the matter density, the amplitude of structure, and the
redshift evolution of dark energy (DE) below $z \leq 1$. Importantly, its parameter degeneracy directions differ from those of shear,
Baryon Acoustic Oscillations (BAO), and
Cosmic Microwave Background (CMB) data, making it a complementary and consistency-check probe with substantial diagnostic value for the next decade of precision cosmology. However, the current potential of magnification bias is restricted by limited sky coverage, catalogue inhomogeneities, and insufficiently precise
redshift or number-count characterisation. A next-generation wide-field submillimetre facility like AtLAST – capable of uniform, deep surveys and spectroscopic mapping – would overcome these limitations and transform magnification bias into a competitive, high-precision cosmological tool.
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All authors Laura Bonavera, Joaquin Gonzalez-Nuevo, Juan Alberto Cano, David Crespo, Rebeca Fernández-Fernández, Valentina Franco, Marcos M. Cueli, José Manuel Casas, Tony Mroczkowski, Caludia Ciccone, Marina Migliaccio, Evanthia Hatziminaoglou, Hugo Messias
Earth and Planetary Astrophysics
ExoMol line lists – LXIII: ExoMol line lists for 12 isotopologues of CO$_2$
Sergei N. Yurchenko, Marco G. Barnfield, Charles A. Bowesman et al. (+9 more)
Extensive rovibrational line lists are constructed for 12 isotopologues of carbon dioxide: $^{12}$C$^{16}$O$_2$, $^{13}$C$^{16}$O$_2$, $^{12}$C$^{17}$O$_2$, $^{13}$C$^{17}$O$_2$, $^{12}$C$^{18}$O$_2$, $^{13}$C$^{18}$O$_2$, $^{16}$O$^{12}$C$^{17}$O, $^{16}$O$^{12}$C$^{18}$O, $^{16}$O$^{13}$C$^{17}$O, $^{16}$O$^{13}$C$^{18}$O, $^{17}$O$^{12}$C$^{18}$O, and $^{17}$O$^{13}$C$^{18}$O. The variational program TROVE was employed together with an exact kinetic energy operator, accurate empirical potential energy surface (Ames-2) and the ab initio dipole moment surface Ames-2021-40K. Empirical energy levels from the most recent MARVEL analyses, as well as from the HITRAN and CDSD databases, are used to replace calculated values where available. The line lists are further supplemented by assigning AFGL
quantum numbers using machine-learning based
estimators. The resulting data were employed to generate opacities with four radiative transfer codes, TauREx, ARCiS, NEMESIS, and petitRADTRANS, both for individual isotopologues and for CO$_2$ at terrestrial isotopic natural abundance. All line lists and associated data are available at www.exomol.com.
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All authors Sergei N. Yurchenko, Marco G. Barnfield, Charles A. Bowesman, Ryan P. Brady, Elizabeth R. Guest, Kyriaki Kefala, Qing-He Ni, Armando N. Perri, Oleksiy A. Smola, Andrei Solokov, Chenyi Tao, Jonathan Tennyson
Astrophysics of Galaxies
The molecular diversity of the ISM in galaxies across cosmic time
Mathilde Bouvier, Yiqing Song, Michael Romano et al. (+7 more)
Submillimetre molecular lines (e.g., CO, HCN, SiO) provide a uniquely powerful view of the physical and chemical processes that govern
star formation (SF) and
galaxy evolution. Yet, our current picture of the molecular universe beyond the Milky Way remains strikingly incomplete: broad chemical inventories exist for only a handful of
galaxies, typically more extreme than the Milky Way, constrained by sensitivity limits and narrow survey strategies. In the 2040s, surveying
galaxies with multi-species, multi-transitions observations across diverse
galactic environments will be crucial to establish effective chemical diagnostics of the various ISM processes from the early universe to $z=0$. Extragalactic astrochemistry provides a uniquely sensitive probe of the physical processes shaping
galaxies, allowing us to understand, species by species, how gas responds to its local environment and how
galaxies grow, transform, and recycle matter over
cosmic time.
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All authors Mathilde Bouvier, Yiqing Song, Michael Romano, Anelise Audibert, Ivana Bešlić, Jakob den Brok, Maria J. Jiménez-Donaire, Daizhong Liu, Enrica Bellocchi, Matus Rybak
Instrumentation and Methods for Astrophysics
The search for dark matter axions from neutron stars in the inner parsecs of the Milky Way with AtLAST
J. De Miguel, E. Hatziminaoglou, J. Prieto-Polo et al. (+2 more)
The magnetospheres of
neutron stars in the
Galactic Center provide an exceptional environment to search for dark matter
axions through their resonant conversion into
photons. The combination of extreme
magnetic fields and high dark matter density in this region creates ideal conditions for
axion-
photon conversion across the centimetre-to-submillimetre wavelength range. Detecting the cumulative emission from these
neutron star populations demands a facility with unprecedented sensitivity, spatial resolution, and broad frequency coverage in the submillimetre domain, capabilities essential to explore a previously inaccessible region of
axion parameter space.
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All authors J. De Miguel, E. Hatziminaoglou, J. Prieto-Polo, J. D. Marrero-Falcón, Abaz Kryemadhi
High Energy Astrophysical Phenomena
A wide-field X-ray search for the Geminga pulsar halo with SRG/ART-XC
Roman Krivonos, Silvia Manconi, Vadim Arefiev et al. (+8 more)
Searches for the putative large-scale X-ray
halo around the Geminga
pulsar have been extensively performed using various narrow field-of-view X-ray
telescopes. In this paper, we present wide-field scanning observation of Geminga with SRG/ART-XC. Our X-ray analysis provides, for the first time, direct imaging of a $3.5^\circ \times 3.5^\circ$ region in the $4-12$ keV energy band, comparable in extent to the expected Geminga emission. The ART-XC observation provides a highly uniform sky coverage without strong vignetting effects. The synchrotron X-ray
halo flux was predicted using a physical model based on particle injection,
diffusion, and cooling over the
pulsar's lifetime, as well as the spectral and spatial properties of the synchrotron X-ray and inverse-Compton gamma-ray emissions. The model is tuned to reproduce existing multiwavelength data from X-ray upper limits and GeV to TeV gamma-ray observations. After accounting for the high particle background and its uncertainties, no significant emission is found in the assumed source region, and X-ray flux upper limits are derived. These limits are less constraining by up to a factor of three with respect to existing results obtained with narrow field-of-view
telescopes and longer exposure times. Nonetheless, we place direct and independent constraints on Geminga's ambient
magnetic field strength, which are compatible with other studies. Our methodology, including simulation for longer observation times, is applied for the first time to the wide field-of-view search for
pulsar halos. Using extensive simulations, we also show that a 68% probability of detecting the Geminga
pulsar halo can be achieved with a 20-day SRG/ART-XC exposure for a 3 $\mu G$
magnetic field.
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All authors Roman Krivonos, Silvia Manconi, Vadim Arefiev, Andrei Bykov, Fiorenza Donato, Ekaterina Filippova, Alexander Lutovinov, Mattia Di Mauro, Kaya Mori, Alexey Tkachenko, Jooyun Woo
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Quantum Walks and Exact RG in de Sitter Space
Daniel Green and Kshitij Gupta
The local physics of light scalar fields in de Sitter space is well described by classical random walks, as expressed through the framework of
Stochastic Inflation. Recent work has clarified how this formalism arises from
quantum field theory (QFT) and the renormalization group (RG), allowing for corrections to this formalism to be determined order by order. Yet, this description is incomplete. For example, the
quantum dynamics of these fields are expected to become important when determining the tail of the probability distribution for the fluctuations. In this paper, we develop the understanding of fields in de Sitter as a
quantum walk in order to bridge the gap between the classical and
quantum description. We use the framework of exact RG to calculate the
evolution equation for the reduced density
matrix of the long wavelength fields. This master equation provides the direct map from light fields to models of
quantum walks. We show how to reduce the master equation to
Stochastic Inflation, and provide a new understanding of how the higher-order corrections arise. In the process, we demonstrate that divergences and secular growth in de Sitter, for both light and heavy fields, can be absorbed by (dynamical) renormalization.
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Solar and Stellar Astrophysics
Evolution of Massive Main-sequence Stars in Rapid Population Synthesis. I. Framework and Implementation
Adam Brček, Ryosuke Hirai, Ilya Mandel et al. (+1 more)
Stars spend most of their lifetime on the main sequence (MS), where hydrogen burning establishes the internal chemical structure that governs the subsequent
evolution. In massive
stars, mass loss through winds and binary interactions can significantly modify this structure during the MS. We present a new MS
evolution framework suitable for rapid binary population synthesis, implemented in the COMPAS code. Building on the semianalytical model of Shikauchi et al., our framework captures the
evolution of the convective core on the MS under arbitrary mass-loss or mass-gain histories, including a treatment for
stellar rejuvenation and MS mergers. This new framework yields more massive helium cores at terminal-age MS, more compact radii in stripped MS
stars, and systematically higher black hole masses than commonly used prescriptions. By providing a more realistic treatment of MS
evolution, this framework improves the physical consistency of massive
stars and binary
evolution in rapid population synthesis.
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All authors Adam Brček, Ryosuke Hirai, Ilya Mandel, Harmony Lower
Astrophysics of Galaxies
Local Group dwarf galaxies as dark matter probes
G. Battaglia, J.M. Arroyo Polonio, R. Pascale et al. (+3 more)
Unveiling the fundamental nature of non-baryonic dark matter (DM) has profound implications for our understanding of the Universe and of the physical laws that govern it. Its manifestation as an additional source of matter necessary to explain astrophysical and cosmological observations indicates either a breakdown of General Relativity or that the current Standard Model of Particle Physics is incomplete. In the standard Cold DM (CDM) paradigm, DM consists of collisionless non-relativistic particles with negligible non-gravitational interactions. This simple hypothesis is very successful on large and intermediate scales, but faces challenges on small
galactic scales. Local Group (LG)
dwarf galaxies can play a fundamental role to elucidate whether these challenges stem from poorly understood fundamental baryonic processes or instead indicate that alternative DM scenarios need to be considered. In particular, a systematic determination of their DM
halo properties as a function of
stellar mass and
star formation histories (SFH) will provide crucial observational
benchmarks for models to deal with the trickiest issue that prevents us from advancing in our understanding of DM nature, i.e. the impact of baryonic processes in altering the properties of the inner regions of DM
haloes. Such systematic study would require assembling accurate l.o.s. velocities (and
metallicities) for several thousands of
stars per
galaxy, for an heterogeneous sample of target
galaxies, spanning order of magnitudes in
stellar mass and covering distances from about 100 kpc to more than 1 Mpc. This calls for both multi-objects spectrographs on 12m-class
telescopes with fov of a few deg2 and a multiplex power in the several 1000s with the capability of providing dense sampling of the innermost regions, as well as for wide-area multi-objects spectrographs with fov of several arcmin2 on 30-40m class
telescopes.
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All authors G. Battaglia, J.M. Arroyo Polonio, R. Pascale, M. Benito, R. Leaman, G. Thomas
Astrophysics of Galaxies
Searching for Intermediate-Mass Black Holes in Milky Way satellites
R. Pascale and G. Battaglia
Intermediate-mass black holes (IMBHs), with masses between roughly $10^2\,M_\odot$ and $10^5\,M_\odot$, represent a largely uncharted component of the black-hole (BH) population. They are theoretically predicted to form in several early-Universe pathways, including the remnants of massive Population III
stars, the runaway collapse of dense
stellar clusters, and the direct collapse of metal-poor gas. Establishing whether IMBHs are present in
dwarf galaxy satellites of the Milky Way (MW), and with what occupation fraction - i.e. the fraction of
galaxies with a certain
stellar mass that host a central BH - provides one of the most incisive tests of BH seed formation models. Despite their importance, present dynamical constraints on IMBHs remain weak. Dynamical IMBH masses or upper limits are available for very few such systems, with secure detections in less than ten cases. A next-generation wide-field spectroscopic facility, capable of combining deep multiplexed
stellar spectroscopy with high-resolution integral-field observations of
galaxy centers, would open access to IMBH masses in the $\leq10\,M_\odot$ regime. Such an advance would make possible - for the first time - a robust measurement of the IMBH occupation fraction in
dwarf galaxies. A key scientific requirement for the coming decades is to establish the observational and instrumental capabilities needed to detect or tightly constrain IMBHs in nearby
dwarf galaxies, particularly in the $\simeq10^3-10^4 \,M_\odot$ mass range, and thereby enable a measurement of their occupation fraction. Such a measurement is fundamental for distinguishing between competing scenarios for the formation of BH seeds in the early Universe.
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Astrophysics of Galaxies
Connection between galaxy morphology and dark-matter halo structure II: predicting disk structure from dark-matter halo properties
Jinning Liang, Fangzhou Jiang, Houjun Mo et al. (+4 more)
We investigate how
galactic disk structures connect to the detailed properties of their host dark-matter
halos using the TNG50 simulation. From the hydrodynamic and matched dark-matter-only runs, we measure a comprehensive list of
halo properties describing density structure, angular momentum, shape, assembly history, and environment. Using the morphological decomposition developed in Paper I, we quantify the sizes, scale heights, and mass fractions of the disk components for
galaxies at $0 \le z \le 4$. Random Forest (RF) regression shows that
halo properties alone predict disk size and thickness with high accuracy, while Symbolic Regression (SR) provides compact empirical relations with slightly lower accuracy. Disk height is consistently easier to predict than disk size, and lower-mass
halos yield higher accuracy than massive
halos. Predictions based on
halo properties measured in the hydro simulations outperform those based on
halos matched in the dark-matter-only simulation, reflecting the imprint of baryonic restructuring on the inner
halo. SHAP analysis reveals the most informative
halo parameters include concentration, Einasto shape, global and inner
spin, and recent mass
accretion, though their importance varies across disk properties. We show correlations between disk size and the density-profile shape arise primarily from disk-induced modification of the inner
halo, rather than a
primordial connection. Finally, we point out that disks become more extended with respect to their host
halos at higher
redshift in low-mass
halos, while massive high-
redshift halos show the opposite trend. We provide SR-based prescriptions that accurately map
halo properties to disk structures, offering practical tools for
galaxy-
halo modeling.
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All authors Jinning Liang, Fangzhou Jiang, Houjun Mo, Andrew Benson, Philip F. Hopkins, Avishal Dekel, Luis C. Ho
Cosmology and Nongalactic Astrophysics
A high-dynamic-range view of the growth of structure and the warm/hot Universe
Luca Di Mascolo, Tony Mroczkowski, Joshiwa van Marrewijk et al. (+23 more)
Baryons heat to temperatures above $>\!\!10^5\,\mathrm{K}$ as they accrete onto massive overdensities –
galaxies, groups, clusters, and filaments – where they ionize and become optically transparent. Deep mm-wave observations such as those with ALMA have begun to probe a handful ($\sim\,$4) of massive systems at $z\!\sim\!2-4$, while low-resolution mm-wave surveys have detected thousands of objects at arcminute resolution out to $z\!\approx\!2$. To truly advance the field of the
evolution of large-scale structures, mapping the warm/hot distribution of ionized gas out to the
redshift of their formation, the ESO community requires a large-aperture single-dish (sub-)mm
telescope. This will need to provide several orders of magnitude higher mapping speeds than currently available while preserving the few arcsecond resolution required for imaging the gas and removing contaminating
radio and dusty thermal signals across the full (sub-)mm wavelength range.
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All authors Luca Di Mascolo, Tony Mroczkowski, Joshiwa van Marrewijk, Rémi Adam, Nabila Aghanim, Stefano Andreon, Eleonora Barbavara, Elia Stefano Battistelli, Esra Bulbul, Jens Chluba, Eugene Churazov, Claudia Cicone, William Coulton, Stefano Ettori, Massimo Gaspari, Ricardo Génova Santos, Matt Hilton, Adam D. Hincks, Eelco van Kampen, Tetsu Kitayama, Minju Lee, John Orlowski-Scherer, Charles Romero, Laura Salvati, Alexandro Saro, Íñigo Zubeldia
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Stellar Superradiance and Low-Energy Absorption in Dense Nuclear Media
Zhaoyu Bai, Vitor Cardoso, Yifan Chen et al. (+3 more)
Ultralight
bosons such as
axions and dark
photons are well-motivated hypothetical particles, whose couplings to ordinary matter can be effectively constrained by
stellar cooling. Limits on these interactions can be obtained by demanding that their emission from the
stellar interior does not lead to excessive energy loss. An intriguing question is whether the same microphysical couplings can also be probed through
neutron star superradiance, in which gravitationally bound bosonic modes grow exponentially by extracting rotational energy from the
star. Although both processes originate from
boson-matter interactions, they probe very different kinematic regimes.
Stellar cooling probes
boson emission at thermal wavelengths, while superradiance is governed by modes whose wavelength is comparable to or greater than the size of the
star. Previous work has attempted to relate the microphysical
neutron-nucleon scattering and inverse-bremsstrahlung absorption rates directly to the macroscopic growth rate of superradiant bound states. In this work, we re-examine this connection and show that a naive extrapolation of the microphysical absorption rate to the superradiant regime would imply superradiant rates comparable to astrophysical timescales characterised by
pulsar spindown. These naive rates are especially high for vector fields. However, we demonstrate that this conclusion changes once collective multiple-scattering effects in dense
nuclear matter are taken into account. Repeated nucleon collisions modify the effective low-energy absorption experienced by the bosonic bound state, strongly suppressing the rate relevant for superradiance.
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All authors Zhaoyu Bai, Vitor Cardoso, Yifan Chen, Yuyan Li, Jamie I. McDonald, Hyeonseok Seong
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Bibhushan Shakya
This paper examines frameworks and phenomenology of ultrarelativistic
Higgs vacuum bubble collisions in a first-order phase transition associated with the Standard Model
Higgs field in the early Universe. Such collisions act as a
cosmic scale
Higgs collider, providing access to energy scales far beyond any temperature reached in our
cosmic history, potentially up to the Planck scale. This provides a unique opportunity to probe new physics that couples to the
Higgs at very high scales, while also enabling novel applications for various cosmological phenomena, opening tremendous opportunities for particle physics and cosmology. As examples, we demonstrate the viability of nonthermal production of ultra-heavy
Higgs portal dark matter up to $10^{16}$ GeV (with observable indirect and direct detection signals up to $m_\text{DM}=O(10)$ TeV), and leptogenesis from the production of GUT scale right-handed
neutrinos.
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Earth and Planetary Astrophysics
Spirals and Vertical Motions in the Planet-Forming Disk around HD 100546. A multi-line study of its gas kinematics
Lisa Wölfer, Andrés F. Izquierdo, Alice Booth et al. (+5 more)
HD100546 represents a particularly interesting target to study dynamical
planet-disk interactions as various features have been observed in both the
dust and gas that provide direct and indirect evidence for ongoing
planet formation. In this work, we aim to characterize the gas kinematics of five molecular CO emission lines observed with ALMA in HD 100546, to reveal deviations from Keplerian rotation as well as substructures in the peak intensity and line width. We fit the molecular intensity channels with the Discminer package to model the line profiles. Aside from fitting the full cube, we also conduct runs where the blue- and redshifted sides are modeled separately to search for possible asymmetries. Our analysis reveals prominent kinematical spiral features in all five lines on large scales of the disk and we reproduce their morphology with both a linear and logarithmic spiral. In 12CO 2-1, spirals are also seen in the peak intensity residuals, the line width residuals exhibit a prominent ring of enhanced line widths around 125-330 au. The models further show, that the emission from the redshifted side may originate from higher disk layers than that from the blueshifted side. The pitch angles of the spirals are consistent with those driven by an embedded companion inside of 50 au and they suggest a dynamical mechanism rather than gravitational instabilities. We further find indications of a companion around 90-150 au, where tentative dips are present in the radial profiles of the integrated intensity of 13CO and C18O and pressure minima are observed in the azimuthal velocities. For the first time, we also detect downward vertical flows in this region, which coincide with the observed
dust gap. The asymmetry in the emission heights may be a result of infall from the disk's environment. Another explanation is provided by a warped inner disk, casting a shadow onto one side of the disk.
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All authors Lisa Wölfer, Andrés F. Izquierdo, Alice Booth, Stefano Facchini, Richard Teague, Ewine F. van Dishoeck, Teresa Paneque-Carreño, Bill Dent
Instrumentation and Methods for Astrophysics
Millimeter-Wavelength Observations of the Active Sun: Unveiling the Origins of Space Weather
Sven Wedemeyer, Stefaan Poedts, Stanislav Gunár et al. (+15 more)
Societal dependence on space-based services demands major advances in predicting the impacts of eruptive
solar events. Millimeter-wavelength observations offer uniquely direct access to the time-dependent physical conditions in the atmospheric layers of the Sun where these events originate. A facility capable of full-disk, high-cadence, multi-frequency imaging would provide a transformative view of the Sun and its influence on the heliosphere. AtLAST is ideally suited to deliver this capability, and to establish a European leadership role in advancing the scientific foundations that will enable reliable, operational space-weather
forecasting for the first time.
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All authors Sven Wedemeyer, Stefaan Poedts, Stanislav Gunár, Manuela Temmer, Astrid Veronig, Valery Nakariakov, Mats Kirkaune, Claudia Cicone, Stephen White, Jasmina Magdalenić, Roman Brajša, Bart De Pontieu, Maryam Saberi, Atul Mohan, Davor Sudar, Galina Motorina, Maria Lukicheva, Paulo Simões
Cosmology and Nongalactic Astrophysics
Buried but not destroyed: the evolution from prompt cusps to NFW haloes
Yuchan Wang, Sownak Bose, Carlos Frenk et al. (+1 more)
The internal structure of dark matter
haloes encodes their assembly history and offers critical insight into the nature of dark matter and structure formation. Analytical studies and high-resolution simulations have recently predicted the formation of '
prompt cusps' - steep power-law density profiles that emerge rapidly from the monolithic collapse of
primordial peaks. Yet, by $z=0$ most
haloes are well described by Navarro-Frenk-White (NFW) density profiles, raising the question of how these early cusps are transformed in a cosmological setting. We address this problem using 64 zoom-in $N$-body simulations of eight
haloes, each resimulated with eight different free-streaming wavenumbers to control the abundance of small-scale structure while keeping the large-scale environment fixed. To mitigate numerical discreteness effects, we classify artificial fragments and genuine subhaloes with a physically motivated procedure based on matching subhaloes to their progenitor peaks. At the population level, we demonstrate that
haloes initially form
prompt cusps, and their profiles subsequently transition towards the NFW form. Our study reveals three distinct pathways by which
prompt cusps evolve: major mergers,
accretion of artificial fragments, and interactions with large-scale filaments, each having a distinct impact on the inner density profile. In particular, we show that the original power-law cusp remains visible in the profile of particles associated with the
primordial peak even when the total
halo profile is already NFW-like. This work highlights the imprint of early collapse on present-day
halo structure and provides new insights into the origin of the universality of the NFW profile.
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All authors Yuchan Wang, Sownak Bose, Carlos Frenk, Adrian Jenkins
Instrumentation and Methods for Astrophysics
How Mass Flows Through Accretion Discs: A Spectral-Timing Vision for the 2040s
Simone Scaringi, Domitilla de Martino, Anna F. Pala et al. (+17 more)
Understanding how mass and angular momentum flow through
accretion discs remains a fundamental unsolved problem in astrophysics. Accreting white
dwarfs offer an ideal laboratory for addressing this question: their variability occurs on accessible timescales of seconds to minutes, and their optical spectra contain continuum and emission-line components that trace distinct disc regions. Broad-band timing studies have revealed time-lags similar to those observed in X-ray binaries and active
galactic nuclei, suggesting propagating fluctuations and possible coupling to an inner hot flow. However, the blending of line and continuum light in broad filters prevents a physical interpretation of these signals. The 2040s will bring an unprecedented number of disc-accreting systems discovered by Rubin-LSST, space-based gravitational-wave observatories, and third-generation ground and space-based detectors. To extract disc physics from these sources, high-cadence optical spectral-timing, simultaneously resolving continuum and individual lines, is essential. Such measurements would directly map how variability propagates through discs, determine how the outer disc responds to changes in the inner flow, and test whether
accretion physics is scale-invariant from white
dwarfs to supermassive black holes. This white paper outlines the scientific motivation and observational capabilities required to realise this
vision. It highlights the opportunity for ESO to enable a transformative new window on
accretion physics in the coming decade.
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All authors Simone Scaringi, Domitilla de Martino, Anna F. Pala, Andrea Sanna, Paul Groot, Kieran O'Brien, Alessandro Ederoclite, Noel Castro Segura, Deanne L. Coppejans, Krystian Ilkiewicz, Piergiorgio Casella, David Buckley, Thomas Kupfer, Nanda Rea, Meryem Kubra DAG, Yusuke Tampo, Siqi Zhang, Sian Ford, Martina Veresvarska, Graham Wynn
Cosmology and Nongalactic Astrophysics
Halo Lightcones with Optimised Orientation and Interpolation in Cosmological Simulations – an application to mock H$\alpha$ selected galaxies
Sujatha Ramakrishnan, Francisco J. Castander, Elizabeth J. Gonzalez et al. (+6 more)
A critical step to create realistic mock catalogs that support large-scale photometric and spectroscopic sky surveys is the production of cosmological simulations that accurately model the survey observables taking into account the
redshift-dependent
galaxy formation and
evolution processes. Here we develop an efficient framework, HOLCon (
Halo Optimised Lightcone Constructor), for post-facto construction of dark matter
halo lightcones from simulations and use them to generate a mock
galaxy catalogue. HOLCon includes a module to optimise the lightcone's orientation within the simulation box, minimising repeated structures when the survey volume exceeds a single box – a common challenge in modern surveys. A linear interpolation scheme tracks the
evolution of
halo properties across snapshots. Applied to the publicly available Uchuu simulation, we construct a lightcone of 50 ${\rm deg}^2$ and extending up to $z = 10$, providing representative coverage of deep fields of Stage IV surveys. We validate the lightcone for cosmological applications by comparing the dark matter
halo clustering in the lightcone with those from the original simulation snapshots. Subsequently, we make the
galaxy-
halo connection on the lightcone with a
redshift extended version of the SciPIC
algorithm producing a comprehensive set of descriptive
galaxy attributes. HOLCon leverages Dask, a scalable parallel computing pythonic framework for fast construction of dark matter
halo lightcones enabling rapid creation of multiple statistical realizations essential for robust cosmological inference. The produced
galaxy mock makes predictions for clustering of H$\alpha$ emitters, making it a useful cosmology resource.
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All authors Sujatha Ramakrishnan, Francisco J. Castander, Elizabeth J. Gonzalez, Martin Eriksen, Zahra Baghkhani, Pablo Fosalba, Jorge Carretero, Gabriele Parimbelli, Pau Tallada-Crespí
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Arturo de Giorgi, Ivan Martinez Soler and Sergio Sevillano Muñoz
In this work, we derive novel constraints on scalar-tensor theories from
neutrino physics. Spatial variations of the background scalar field effectively generate density and position-dependent Standard Model masses, including
neutrinos.
Neutrinos are a unicum in the SM due to their ability both to propagate over
galactic distances and to traverse dense media such as Earth. This makes them an ideal probe of the background scalar field, which can in turn alter flavour oscillations and
supernova time delays. As we enter the era of precision
neutrino physics, we are compelled to explore such a scenario. We derive expressions for the relevant observables and obtain new bounds on a broad class of scalar-tensor models. We finally map the bounds to popular screening mechanisms models, such as the Symmetron and Chameleon.
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