Astrophysics of Galaxies
The mysterious Globular Cluster population of MATLAS-2019
Sergio Guerra Arencibia, Mireia Montes, Giulia Golini et al. (+1 more)
MATLAS-2019 (also known as NGC5846-UDG1) has attracted significant
attention due to the ongoing debate surrounding its Globular Cluster (GC) population, with several studies addressing the issue yet reaching little consensus. In this paper we take advantage of HST's multi-wavelength coverage (F475W, F606W and F814W observations) with the addition of deep u-band imaging from Gran Telescopio de Canarias, to perform the most detailed study and estimation to date of the GC population of the ultra-diffuse
galaxy MATLAS-2019. The improved constraints provided by the combination of high spatial resolution and better coverage of the GC spectral energy distribution has allowed us to obtain a clean sample of GCs in this
galaxy. We report a number of 33+-3 GCs in MATLAS-2019, supporting the previous lower estimates for this
galaxy. The GC population of this
galaxy is highly concentrated with ~80% of the GCs inside the effective radius (Re) of the
galaxy and the GC half-number radius Re,GC is 0.7Re. Using the GC-
Halo mass relation, we estimate a
halo mass for MATLAS-2019 of (1.14+-0.1)x10**11
solar masses. The GC luminosity function and the distribution of effective radii of the GCs favour a distance to the
galaxy of 20.0+-0.9 Mpc. In agreement with previous findings, we find that the distribution of GCs is highly asymmetric even though the distribution of
stars in the
galaxy is symmetric. This suggests that assumptions about the
symmetry of the GC distribution may be incorrect when used to calculate the number of GCs with such low statistics.
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All authors Sergio Guerra Arencibia, Mireia Montes, Giulia Golini, Ignacio Trujillo
Astrophysics of Galaxies
ClearPotential: Revealing Local Dark Matter in Three Dimensions
Eric Putney, David Shih, Sung Hak Lim et al. (+1 more)
We present ClearPotential, a data-driven, three-dimensional measurement of the gravitational potential of the local Milky Way using unsupervised machine learning, without the
symmetry assumptions, specific functional forms, and binning required in previous work. The potential is modeled as a neural network, optimized to solve the
equilibrium collisionless Boltzmann equation for the observed phase space density of
Gaia DR3 Red Clump
stars within 4 kpc of the Sun. This density is obtained from data using normalizing flows, and our unsupervised solution to the Boltzmann equation automatically corrects for selection effects from crowding and the
dust-driven extinction of starlight. Our fully-differentiable model of the gravitational potential allows us to map the acceleration and mass density of the
Galaxy in the volume around the Sun, including in the
dust-obscured disk towards the
Galactic Center. We determine the dark matter density at the
Solar radius to be $(0.84 \pm 0.08)\times 10^{-2}\,{M}_\odot/{\rm pc}^3$, and analyze the structure of the dark matter
halo. We find strong evidence for a tilted oblate
halo, weak preference for a cored inner profile, and the strongest constraints to date on a possible dark matter disk. We place a bound on the timescale of disequilibrium in the local Milky Way, and find mild evidence for disequilibrium using independent acceleration measurements from timings of binary
pulsar systems. This work provides the clearest map of the local
Galactic potential to date and marks an important step in the era of data-driven astrometry.
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All authors Eric Putney, David Shih, Sung Hak Lim, Matthew R. Buckley
Astrophysics of Galaxies
Orbital migration and heating history of the Galactic disc: a transition between the bimodal discs
HanYuan Zhang, Vasily Belokurov, Jason L. Sanders et al. (+7 more)
Stellar orbits in the
Galactic disc evolve from their birth to the current shape through both radial migration and dynamical heating. The history of their secular
evolution is imprinted in the current kinematics and age-
metallicity distribution. We construct a chrono-chemo-dynamical model of the disc, incorporating inside-out growth,
metallicity evolution, radial migration, and heating to fit the observed age-
metallicity-kinematics distribution of LAMOST subgiant
stars in both the low and high-$\alpha$ disc. By modelling all distribution parameters with spline fitting, we present the first non-parametric
stellar migration and heating history of the
Galaxy. We determine the heating-to-migration ratio, the ratio of the root-mean-square changes in radial/vertical and azimuthal actions, to be $\approx0.075$ for radial to azimuthal actions and $\approx0.015$ for vertical to azimuthal actions, implying a highly anisotropic
diffusion in the action space. Furthermore, we identify a transition in radial migration efficiency coinciding with the transition moment of the bimodal disc, for which the radial migration was more efficient for the high-$\alpha$ disc than for the low-$\alpha$ disc. This transition may be attributed to two correlated scenarios: 1) a bar formation epoch accompanied by violent outward migration, and 2) a drop in the gas mass fraction in the disc when the low-$\alpha$ disc began to form. These findings offer further constraints on the formation mechanisms of bimodal discs, favouring the downsizing scenario. We also briefly discuss the connection between our results and recent high-
redshift observations. In addition to the secular
evolution history, our model maps the Milky Way ISM
metallicity gradient at different lookback times, which we find has only varied a little (in the range of $-0.07~\rm to~-0.10~dex/kpc$) since disc formation.
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All authors HanYuan Zhang, Vasily Belokurov, Jason L. Sanders, N. Wyn Evans, David Chemaly, Daisuke Kawata, Natsuki Funakoshi, Neige Frankel, Sarah G. Kane, Sergey E. Koposov
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Dark matter mounds from the collapse of supermassive stars: a general-relativistic analysis
Roberto Caiozzo, Gianfranco Bertone, Piero Ullio et al. (+3 more)
Recent work has highlighted the importance of a fully relativistic treatment of the dephasing of gravitational waves induced by dark-matter overdensities in extreme mass-ratio inspirals (EMRIs). However, a general-relativistic description of the dark matter phase-space distribution is currently available only for the case of a dark matter "spike" arising from adiabatic black hole growth. Here we develop a fully general-relativistic formalism for the more realistic scenario in which a supermassive
stellar progenitor collapses to a black hole and produces a shallower dark matter overdensity, or "mound". We follow self-consistently the
evolution of the supermassive
star, its collapse, and the subsequent growth of the resulting black hole, together with the collisionless dark matter orbits. We find that in the regime where the collapse becomes non-adiabatic, the dark matter distribution function is significantly reshaped, with a clear depletion in the low-binding-energy region of phase space. Our results provide a more realistic prediction for the dark matter phase-space distribution around supermassive black holes, which is an essential step in our programme to use future EMRI observations to extract information about both the nature of dark matter and the formation history of the black hole.
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All authors Roberto Caiozzo, Gianfranco Bertone, Piero Ullio, Rodrigo Vicente, Bradley J. Kavanagh, Daniele Gaggero
Cosmology and Nongalactic Astrophysics
Clues from $\mathcal{Q}$–A null test designed for line intensity mapping cross-correlation studies
Debanjan Sarkar, Ella Iles and Adrian Liu
Estimating the auto power spectrum of cosmological tracers from line-intensity mapping (LIM) data is often limited by instrumental noise, residual foregrounds, and systematics. Cross-power spectra between multiple lines offer a robust alternative, mitigating noise bias and systematics. However, inferring the auto spectrum from cross-correlations relies on two key assumptions: that all tracers are linearly biased with respect to the matter density field, and that they are strongly mutually correlated. In this work, we introduce a new diagnostic statistic, \(\mathcal{Q}\), which serves as a data-driven null test of these assumptions. Constructed from combinations of cross-spectra between four distinct spectral lines, \(\mathcal{Q}\) identifies regimes where cross-spectrum-based auto-spectrum reconstruction is unbiased. We validate its behavior using both analytic toy models and simulations of LIM observables, including
star formation lines ([CII], [NII], [CI],[OIII]) and the 21-cm signal. We explore a range of
redshifts and instrumental configurations, incorporating noise from representative surveys. Our results demonstrate that the criterion \( \mathcal{Q} \approx 1 \) reliably selects the modes where cross-spectrum
estimators are valid, while significant deviations are an indicator that the key assumptions have been violated. The \( \mathcal{Q} \) diagnostic thus provides a simple yet powerful data-driven consistency check for multi-tracer LIM analyses.
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Astrophysics of Galaxies
KURVS: chemical properties from multiple strong line calibrations for star-forming galaxies at $z\sim1.5$
Zefeng Li, Ugnė Dudzevičiūtė, Annagrazia Puglisi et al. (+13 more)
Gas-phase oxygen abundance (
metallicity) properties can be constrained through emission line analyses, and are of great importance to investigate
galaxy evolution histories. We present an analysis of the integrated and spatially-resolved rest-frame optical emission line properties of the ionised gas in 43
star-forming
galaxies at $z\sim1.5$ in the KMOS Ultra-deep Rotational Velocity Survey (KURVS). Using the [NII]$\lambda6584$/H$\alpha$ (N$_2$), ([OII]$\lambda\lambda3727,9+$[OIII]$\lambda\lambda4959,5007$)/H$\beta$ (R23), and for the first time [NII]$\lambda6584$/[OII]$\lambda\lambda3727,9$ (N$_2$O$_2$) indicators at this
redshift, we measure the gas-phase
metallicities and their radial gradients. On $\sim4$-kpc scales
metallicity gradients measured from N$_2$O$_2$ and those measured from N$_2$ are in good agreement when considering the spatial distributions of
dust in each
galaxy, as parameterised by
dust attenuation radial gradients. We report a nearly flat
metallicity gradient distribution typically at $z\sim1.5$, with the 50th, 16th and 84th percentiles at $0.01$, $-0.03$, and $0.05$ dex kpc$^{-1}$, respectively. The findings agree well with previous observational studies and simulations at this epoch. We ascribe the observed negative
metallicity gradients to a natural result from self-regulating systems, and the positive ones to potential
galactic fountains and higher merger rates.
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All authors Zefeng Li, Ugnė Dudzevičiūtė, Annagrazia Puglisi, Steven Gillman, A. Mark Swinbank, Luca Cortese, Ian Smail, Karl Glazebrook, Anna F. McLeod, Dominic J. Taylor, Roland Bacon, Christopher Harrison, Edo Ibar, Juan Molina, Danail Obreschkow, Tom Theuns
Astrophysics of Galaxies
Rhea-RT: Dynamical impact of Central Molecular Zone conditions on the properties of the interstellar medium and stellar feedback coupling
R.G. Tress, N. Brucy, P. Girichidis et al. (+22 more)
The Central Molecular Zone (CMZ) is an extreme
star formation environment, characterized by higher density, higher
turbulence, stronger orbital shear, and stronger
magnetic field strength than the
solar neighborhood. It is still debated whether classical theories of
star formation hold within this extreme environment. In order to assess the impact of these different conditions on the interstellar medium (ISM) and on
star formation, we present radiation magnetohydrodynamic arepo simulations of a Milky Way-type
galaxy. We set up a high-resolution ($M_{\rm cell}=20$~\Msun) region in a ring around the
solar radius and in the barred region of the
Galaxy to have a coherent comparison between the CMZ and the
solar neighborhood. Although the high densities and strong levels of
turbulence affect
star formation and feedback, a key difference in the regulation of
star formation between the two environments comes from the short orbital times and the strong shear in the CMZ. In particular, we highlight the role of the quick dynamical decoupling of
stars and gas, which leads to periodic re-
embedding events in the early lifetimes of radiating O
stars. Young
stellar associations are efficiently sheared apart, such that the ISM is deprived of the compounding effect of radiation and
supernovae in disrupting molecular clouds. This dramatically changes the
evolution of
giant molecular clouds and how feedback can regulate
star formation in the CMZ.
Stellar feedback is no longer directly coupled to the molecular cloud from which they formed, and no strong and disruptive superbubbles can develop. The feedback instead rather acts as a background source of
turbulence.
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All authors R.G. Tress, N. Brucy, P. Girichidis, S.C.O. Glover, J. Goeller, M. Hirschmann, R. Klessen, T. Peter, J. Petersson, M.C. Sormani, L. Armillotta, C.D. Battersby, M. Donati, Z.X. Feng, J.D. Henshaw, D.R. Lipman, S.N. Longmore, F. Nogueras-Lara, V.M. Pelkonen, N. Peschken, M.A. Petkova, A. Plat, S. Reissl, R. Smith, J.D. Soler
Cosmology and Nongalactic Astrophysics
UV Luminosity Functions from HST and JWST: A Possible Resolution to the High-Redshift Galaxy Abundance Puzzle and Implications for Cosmic Strings
Mattéo Blamart, Adrian Liu, Robert Brandenberger et al. (+2 more)
Recent observations of high
redshift galaxies by the James Webb Space
Telescope suggest the presence of a bright population of
galaxies that is more abundant than predicted by most
galaxy formation models. These observations have led to a rethinking of these models, and numerous astrophysical and cosmological solutions have been proposed, including
cosmic strings, topological defects that may be remnants of a specific phase transition in the very early moments of the Universe. In this paper, we integrate
cosmic strings, a source of nonlinear and non-Gaussian perturbations, into the semi analytical code Zeus21, allowing us to efficiently predict the ultraviolet luminosity function (UVLF). We conduct a precise study of parameter degeneracies between
star-formation astrophysics and
cosmic-string phenomenology. Our results suggest that
cosmic strings can boost the early-
galaxy abundance enough to explain the measured UVLFs from the James Webb and Hubble Space
Telescopes from
redshift z = 4 to z = 17 without modifying the
star-formation physics. In addition, we set a new upper bound on the string tension of $G\mu \lessapprox 10^{-8}$ ($95\%$ credibility), improving upon previous limits from the
cosmic microwave background. Although with current data there is some level of model and prior dependence to this limit, it suggests that UVLFs are a promising avenue for future observational constraints on
cosmic-string physics.
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All authors Mattéo Blamart, Adrian Liu, Robert Brandenberger, Julian B. Muñoz, Bryce Cyr
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Gravitational-wave parameter estimation to the Moon and back: massive binaries and the case of GW231123
Francesco Iacovelli, Jacopo Tissino, Jan Harms et al. (+1 more)
We study the prospects of the Lunar Gravitational-Wave
Antenna (LGWA), a proposed deci-Hz GW detector, to observe binary black holes (BBHs) and enable multiband science with ground-based detectors. We assess the detectability of the events observed by current instruments up to the GWTC-4.0 data release, and of simulated populations consistent with the latest reconstruction by the LIGO-Virgo-KAGRA Collaboration. We find that LGWA alone would have been able to observe more than one third of the events detected so far, and that it could detect $\sim\!90$ events merging in the ground-based band per year out to
redshifts $z\sim3-5$. Current detectors at design sensitivity and 100% duty cycle could detect thousands of BBHs per year, with one to a few hundred multiband counterparts in LGWA. Third-generation (3G) detectors can observe most of the BBHs detected by LGWA merging in their frequency band in the simulated mass range $7\,{\rm M}_\odot\lesssim M_{\rm tot}\lesssim 600\,{\rm M}_\odot$, enabling systematic joint analyses of hundreds of events. The short time to merger from the deci-Hz band to the Hz-kHz band (typically months to a year) allows for early warning, targeted follow-up, and archival searches. Multiband observations of intermediate-mass BBHs in the deci-Hz band are particularly promising. We perform an injection study for a GW231123-like system (the most massive BBH detection to date, which accumulates $\sim 10^5$ inspiral cycles in LGWA) and show that deci-Hz observations can measure the chirp mass even better than 3G instruments and yield good sky localization and inclination measurement, even with a single observatory. Opening the deci-Hz band would substantially improve the prospects of GW astronomy for intermediate-mass BBHs.
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All authors Francesco Iacovelli, Jacopo Tissino, Jan Harms, Emanuele Berti
Instrumentation and Methods for Astrophysics
Decisively Demonstrating Roman CGI's TTR5 Requirement by Reimaging a Newly-Discovered Brown Dwarf Orbiting a Bright Accelerating Star
Thayne Currie, Mona El Morsy, Brianna Lacy et al. (+3 more)
We propose Roman Coronagraph project HLC/575 nm observations of a newly-discovered brown
dwarf (HIP 71618 B) from the Subaru/OASIS survey of young accelerating
stars, which is supported by NASA headquarters with the directive to identify targets for the Roman Coronagraph that could fulfill TTR5 requirements and be observed during the technology demonstration phase. The target and multiple bright PSF references are within/close to the Roman Continuous Viewing Zone. A high SNR detection of this companion would singlehandedly fulfill TTR5 and would be the first optical detection of a companion at $<$10$^{-6}$ contrast. Roman CPP reference
star vetting prioritizing
stars that can be paired with HIP 71618 would aid the execution of a successful technology demonstration. Additional similar targets may be discovered from OASIS over the next few years that could increase CGI scheduling flexibility and enhance its scientific and technical return. A close collaborative partnership with the CPP team could ensure that they are schedulable.
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All authors Thayne Currie, Mona El Morsy, Brianna Lacy, Masayuki Kuzuhara, Naoshi Murakami, Danielle Bovie
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Do SN 1987A data yield the three neutrino masses?
Robert Ehrlich
Currently only upper limits are known for the
neutrino masses based on cosmological constraints and direct
neutrino mass experiments. This review explores the possibility that SN 1987A might provide actual values for the three
neutrino masses and not just upper limits, a possibility first suggested by Ramanath Cowsik in 1988. Cowsik's result depends on the
neutrino emissions from SN 1987A being near-simultaneous, i.e., within a time interval $\Delta t<1 s.$ Having such a brief burst, however, is contradicted by virtually all
supernova neutrino emission models that include a $\Delta t>10 s$ cooling phase. Here it is explained why those
neutrino emission models may be mistaken, and why the three
neutrino masses suggested by the SN 1987A data might be correct even though they are larger than the upper limits implied from cosmology and direct mass experiments.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.pop-ph
The Eschatian Hypothesis
David Kipping
The history of astronomical discovery shows that many of the most detectable phenomena, especially detection firsts, are not typical members of their broader class, but rather rare, extreme cases with disproportionately large observational signatures. Motivated by this, we propose the Eschatian Hypothesis: that the first confirmed detection of an extraterrestrial technological civilization is most likely to be an atypical example, one that is unusually "loud" (i.e., producing an anomalously strong technosignature), and plausibly in a transitory, unstable, or even terminal phase. Using a toy model, we derive conditions under which such loud civilizations dominate detections, finding for example that if a society is loud for only $10^{-6}$ of its lifetime, it must emit ${\gtrsim}1$% of its total observable energy budget during that phase to outrun quieter populations. The hypothesis naturally motivates agnostic anomaly searches in wide-field, multi-channel, continuous surveys as a practical strategy for a first detection of extraterrestrial technology.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Blandford-Znajek Jets and the Total Angular Momentum Evolution of a Black Hole Connected to a Cosmic String
Ishan Swamy and Deobrat Singh
Rotating black holes with strong
magnetic fields lead to an outward energy flux in the form of jets governed by the Blandford-Znajek mechanism. These jets depend on factors such as
accretion rate,
magnetic flux and the
spin of the black hole. When such rotating black holes get attached to a
cosmic string, it leads to a further rotational energy extraction, leading to a reduced
spin. We consider such a system and investigate the effect this reduced
spin has on the jet power and its dependence on the
cosmic string tension, $\mu$. It is shown that for a constant
magnetic flux and
accretion rate, the jet energy flux is inversely proportional to $\mu^2$. Interestingly, the rate of this energy flux varies with time and is again dependent on $\mu$. We also study the total angular momentum
evolution of the black hole by considering four major effects:
accretion, jets,
cosmic string energy extraction and the Bardeen-Petterson effect. Further, we attempt to analyse the condition for the
spin-down of a black hole due to these effects and find out that it is possible for both small and large string tensions, with a higher possibility for larger string tensions. Another interesting phenomenon that has been proposed is the
alignment of the jet with the
cosmic string. Additionally, the Bardeen-Petterson effect also leads to
alignment or misalignment of the inner and outer disks depending on the
alignment of the string. In this manuscript we propose that these results might have an observable effect and hence could serve as a potential detection method for
cosmic strings.
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Cosmology and Nongalactic Astrophysics
Self-calibration of weak lensing cosmic shear biases
Giuseppe Congedo and Andy Taylor
In order to reach the required performance of Stage-III and IV weak
lensing surveys,
cosmic shear measurements have to rely on external simulations to calibrate residual biases. Over the years, several techniques have been developed to mitigate the impact of residual biases prior to calibration, including the inference of shear responses on images to correct multiplicative biases, and the empirical correction of additive biases. We introduce a novel methodology that generalises upon the state-of-the-art approaches by inferring multiplicative and additive biases jointly from parameterised distributions of measured ellipticities, crucially without relying on external simulations and independently from cosmology. Shear biases are marginalised over the unknown hyper-parameters in the modelling, hence mitigating the impact of degeneracies. We apply the technique to a representative problem and show the performance of the estimation, even in the presence of noise. The method has a high potential for applicability to the calibration of weak
lensing cosmic shear in current and future
lensing surveys.
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Cosmology and Nongalactic Astrophysics
Self-consistent secondary cosmic microwave background anisotropies and extragalactic foregrounds in the FLAMINGO simulations
Tianyi Yang, Ian G. McCarthy, Fiona McCarthy et al. (+6 more)
Secondary anisotropies in the
cosmic microwave background (CMB) contain information that can be used to test both cosmological models and models of
galaxy formation. Starting from lightcone-based HEALPix maps and catalogues, we present a new set of mock CMB maps constructed in a self-consistent manner from the FLAMINGO suite of cosmological hydrodynamical simulations, including CMB
lensing, thermal and kinetic Sunyaev-Zeldovich effects,
cosmic infrared background,
radio point source and anisotropic screening maps. We show that these simulations reproduce a wide range of observational constraints. We also compare our simulations with previous predictions based on dark matter-only simulations which generally model the secondary anisotropies independently from one another, concluding that our hydrodynamical simulation mocks perform at least as well as previous mocks in matching the observations whilst retaining self-consistency in the predictions of the different components. Using the model variations in FLAMINGO, we further explore how the signals depend on cosmology and feedback modelling, and we predict cross-correlations between some of the signals that differ significantly from those in previous mocks. The mock CMB maps should provide a valuable resource for exploring correlations between different secondary anisotropies and other large-scale structure tracers, and can be applied to forecasts for upcoming surveys.
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All authors Tianyi Yang, Ian G. McCarthy, Fiona McCarthy, Boris Bolliet, Jens Chluba, William Coulton, John C. Helly, Matthieu Schaller, Joop Schaye
Astrophysics of Galaxies
Clumpy, dense gas in the outflow of NGC 1266
Justin Atsushi Otter, Katherine Alatalo, Kate Rowlands et al. (+23 more)
Outflows are one of the most spectacular mechanisms through which active
galactic nuclei (AGN) impact their host
galaxy, though the role of AGN-driven
outflows in global
star formation regulation across the
galaxy population is unclear. NGC 1266 is an excellent case study for investigating the
outflows and
star formation quenching because it is a nearby (D\sim30 Mpc) AGN host
galaxy with an
outflow driving shocks through the interstellar medium (ISM) and has recently quenched its
star formation outside the
nucleus. While previous works have studied the molecular
outflow from its CO emission, to fully characterize the impact the
outflow has on the ISM observations probing the dense, cold gas are necessary. Our ALMA cycle 0 observations do not detect a molecular
outflow in 13CO(2-1) and yield a lower limit 12CO/13CO \geq 250, suggesting a highly optically thin CO
outflow with low 13CO abundance. In contrast, we detect substantial HCN(1-0) emission in the
outflow, with an HCN(1-0)/12CO(1-0) ratio of 0.09, consistent with global measurements of many
star-forming
galaxies and Luminous InfraRed
Galaxies (LIRGs). We conclude that the CO emission traces a diffuse component of the molecular gas with a low optical depth, whereas the HCN(1-0) traces dense clumps of gas entrained in the
outflow. We measure an upper limit molecular
outflow rate of < 85 Msun/yr. Assuming the ongoing
nuclear star formation and
outflow continue at the same rates, NGC 1266 will deplete its gas reservoirs in 450 Myr or longer, indicating that relatively low-level AGN feedback is capable of gradually expelling the molecular gas reservoir after a rapid quenching event.
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All authors Justin Atsushi Otter, Katherine Alatalo, Kate Rowlands, Pallavi Patil, Maya Skarbinski, Lauren Dysarz, Mark Lacy, Maria J. Jimenez-Donaire, Susanne Aalto, Timothy A. Davis, Antoniu Fodor, K. Decker French, Nanase Harada, Timothy Heckman, Ryo Kishikawa, Sebastian Lopez, Yuanze Luo, Sergio Martin, Anne M. Medling, Kristina Nyland, Andreea Petric, Namrata Roy, Mamiko Sato, Elizaveta Sazonova, Adam Smercina, Akshat Tripathi
Instrumentation and Methods for Astrophysics
GFH-v2 Pipeline for Searches of Long-Transient Gravitational Waves from Newborn Magnetars
Sandhya Sajith Menon, Lorenzo Pierini, Pia Astone et al. (+11 more)
This paper presents an enhanced methodology for searching long transient gravitational waves associated with a newborn magnetar, with particular focus on the regime in which the early
spin-down is dominated by gravitational-wave emission. The analysis is performed using a strongly improved version of the generalized Frequency Hough Transform
algorithm, called GFH-v2. We describe the main developments introduced relative to the original implementation and outline the optimized parameter-space selection used in the search. We then compute the theoretical sensitivity of the method and compare it with an empirical sensitivity estimate obtained by injecting simulated signals into LIGO-Virgo-KAGRA O4a data. The updated framework achieves improved sensitivity and computational performance. These results provide a robust basis for future directed searches for long-transient gravitational-wave signals from core-collapse
supernovae and other transient events in current and upcoming observing runs.
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All authors Sandhya Sajith Menon, Lorenzo Pierini, Pia Astone, Cristiano Palomba, Lorenzo Silvestri, Sabrina D'Antonio, Simone Dall'Osso, Francesco Safai Tehrani, Stefano Dal Pra, Gaetano Dinatale, Sergio Frasca, Dafne Guetta, Paola Leaci, Alessio Orlandi
Earth and Planetary Astrophysics
Binary asteroids in mean-motion resonances
Natasa Todorovic and Ivana Milic Zitnik
The purpose of this study is to investigate the relation between binary asteroids and mean motion resonances (MMRs). For more than 700 asteroids from two catalogues, the Johnston Archive [Johnston, 2024] and the
Gaia DR3 VizieR list of binary candidates from Liberato et al. [2024], we applied a resonance identification
algorithm, treating all planetary perturbations. Our results showed that the presence of binary asteroids in MMRs largely depends on their dynamical class. The highest percentage, more than 30%, is found in the Trans- Neptunian region, where most of these objects have exhibited resonant librations longer than 10 Myr. For the main-belt asteroid pairs, this percentage is about 10-12%. Contrary to expectations, the more unstable region populated with NEOs, showed a higher percentage of resonant pairs (above 17%), but with temporal resonant captures. These results could indicate that the mean motion resonances, particularly the stronger ones, could play a role in the
evolution and formation of binary systems. Finally, we highlight that in the present paper, 82 resonant binary asteroids are newly identified.
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Cosmology and Nongalactic Astrophysics
Beyond Two Parameters: Revisiting Dark Energy with the Latest Cosmic Probes
Hanyu Cheng, Supriya Pan and Eleonora Di Valentino
Dark energy (DE) models with many free parameters are often considered excessive, as constraining all parameters poses a significant challenge. While such models offer greater flexibility to probe the DE sector in more detail. With the rapid advancement of astronomical surveys and the availability of diverse
datasets, it is timely to examine whether current combined observations can effectively constrain an extended parameter space in DE models. This article investigates a four-parameter dynamical DE model that spans a broad region of the universe's expansion history through four key parameters: present-day value of the DE equation of state ($w_0$), its initial value ($w_m$), scale factor depicting transition from $w_m$ to $w_0$ ($a_t$), and steepness of this transition ($\Delta_{\rm de}$). We constrain the model using
cosmic microwave background data from Planck, BAO from DESI DR2, and three distinct compilations of Type Ia
Supernovae: PantheonPlus, DESY5, and Union3. Our results show that constraining all four parameters remains challenging: $a_t$ is not constrained by any
dataset, constraints on $w_m$ and $\Delta_{\rm de}$ remain weak, only $w_0$ is well constrained across all
datasets. The results further show that $w_0 > -1$, while $w_m$ is negative, indicating a phantom-like behaviour at early times. Interestingly, despite its larger parameter space, the proposed model shows a preference over the $\Lambda$CDM and $w_0w_a$CDM scenarios for certain combined
datasets, according to both $\Delta \chi^2$ and
Bayesian evidence, although this preference is not strong.
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Solar and Stellar Astrophysics
The Limits of Line Broadening: Modeling Stellar Spectra and Formation Temperatures at High Resolution
Michael L. Palumbo III
The modeling of
stellar spectra is pervasive in astronomy. Conventionally, the shapes of absorption lines are modeled by convolving thermal profiles (computed given some model
stellar atmosphere and line list) with broadening kernels intended to account for the effects of rotation and other nonthermal sources of broadening (i.e., macroturbulence). Here, we show that the assumptions that permit this convolution can break down at high spectral resolution and produce appreciable errors in the modeled flux. We then consider the effects of rotation, microturbulence, and macroturbulence on the intensity and flux contribution functions, which astronomers use to map individual spectral segments to quasi-physical formation "locations" in the
stellar atmosphere. We show that proper consideration of 1) the distinction between intensity and flux and 2) the inclusion of rotation and macroturbulence in the contribution function can dramatically change the modeled formation temperatures. To complement this analysis, we provide a package – FormationTemperatures – which quickly computes model line contribution functions and formation parameters given bulk
stellar properties as input. In closing, we emphasize the assumptions inherent to this analysis, consider in which regimes the convolution expression for flux should be avoided, and caution how the concept of a singular "formation temperature" can oversimplify some realities of radiative transfer.
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Cosmology and Nongalactic Astrophysics
Primordial non-Gaussianity – Fast simulations and persistent summary statistics
Juan Calles, Gabriella Contardo, Jorge Noreña et al. (+2 more)
We investigate the sensitivity of topological and traditional summary statistics to
primordial non-Gaussianity (PNG) using two suites of simulations. First, we introduce a new simulation suite for PNG, PNG-pmwd, comprising more than $20{,}000$
halo catalogs that vary individually local and equilateral shapes, together with variations in $\Omega_m$ and $\sigma_8$. Second, we carry out a systematic comparison of topological descriptors, as well as powerspectrum and bispectrum measurements, evaluating their constraining power on both local and equilateral $f_{\rm NL}$ and how this sensitivity varies with
halo mass. This
dataset enables likelihood-free neural regression of $f_{\rm NL}$ across multiple
halo mass bins for a wide range of summary statistics. Third, we assess the transferability of these learned mappings by testing whether models trained on fast pmwd simulations can robustly infer on simulations from the QuijotePNG suite. We find that a combination of simple descriptive statistics of the topological features (PD-statistics) leads to the best performance to constrain equilateral PNG. We observe that the constraining power of these summaries comes from large-mass
halos, with small-mass
halos adding noise and degrading performance. Similarly, we find that the transferability of the learned mappings, for both topological and powerspectrum plus bispectrum, degrades if small scales or small-mass
halos are included.
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All authors Juan Calles, Gabriella Contardo, Jorge Noreña, Jacky H. T. Yip, Gary Shiu
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Relativistic accretion process onto rotating black holes in Einstein-Euler-Heisenberg nonlinear electrodynamic gravity
Orhan Donmez, G. Mustafa, Himanshu Chaudhary et al. (+4 more)
In this study, we uncover the
accretion dynamics and oscillatory behavior around rotating black holes within the EEH nonlinear electrodynamic framework by analyzing both the motion of test particles and numerically solving the general relativistic hydrodynamic equations. Using EEH geometry, we compute the structure of circular motion, the effective potential and force, and we evaluate the orbital, radial, and vertical epicyclic frequencies together with the Lense-Thirring and periastron precession rates. Our calculations show that, compared to the Kerr model, the charge parameter $Q$ and the
spin parameter $a$ significantly modify the strong gravitational field and shift the characteristic frequencies. We then model the dynamical structure formed by matter accreting toward the EEH black hole through the BHL mechanism, finding that the parameter $Q$ increases the amount of infalling matter and strengthens shock-cone instabilities near the horizon, while farther from the black hole it suppresses
accretion and reduces
turbulence. Time-series analysis of the
accretion rate reveals robust QPOs, whose low-frequency components arise from the precession of the shock cone, while high-frequency components appear as a consequence of strong-field instabilities modified by $Q$ and $a$. A systematic parameter-space exploration identifies the regions where EEH corrections maximize QPO activity, indicating that nonlinear electrodynamics can leave observable imprints on
accretion flows and may be testable with QPO and horizon-scale observations.
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All authors Orhan Donmez, G. Mustafa, Himanshu Chaudhary, M. Yousaf, Abdelmalek Bouzenada, Allah Ditta, Farruh Atamurotov
Earth and Planetary Astrophysics
The Oxygen Valve on Hydrogen Escape Since the Great Oxidation Event
Gregory J. Cooke, Dan R. Marsh, Catherine Walsh et al. (+2 more)
The Great Oxidation Event (GOE) was a $200$ Myr transition circa 2.4 billion years ago that converted the Earth's anoxic atmosphere to one where molecular oxygen (O$_2$) was abundant (volume mixing ratio $>10^{-4}$). This significant rise in O$_2$ is thought to have substantially throttled hydrogen (H) escape and the associated water (H$_2$O) loss. Atmospheric estimations from the GOE onward place O$_2$ concentrations ranging between 0.1% to 150% PAL, where PAL is the present atmospheric level of 21% by volume. In this study we use WACCM6, a three-dimensional Earth System Model to simulate Earth's atmosphere and predict the
diffusion-limited escape rate of hydrogen due to varying O$_2$ post-GOE. We find that O$_2$ indirectly acts as a control valve on the amount of hydrogen atoms reaching the homopause in the simulations: less O$_2$ leads to decreased O$_3$ densities that reduce local tropical tropopause temperatures by up to 17 K, which increases H$_2$O freeze-drying and thus reduces the primary source of hydrogen in the considered scenarios. The maximum differences between all simulations in the total H mixing ratio at the homopause and the associated
diffusion-limited escape rates are a factor of 3.2 and 4.7, respectively. The prescribed CH$_4$ mixing ratio (0.8 ppmv) sets a minimum
diffusion escape rate of $\approx 2 \times 10^{10}$ mol H yr$^{-1}$, effectively a negligible rate when compared to pre-GOE estimates ($\sim10^{12}-10^{13}$ mol H yr$^{-1}$). Because the changes in our predicted escape rates are comparatively minor, our numerical predictions support geological evidence that the majority of Earth's hydrogen escape occurred prior to the GOE. Our work demonstrates that estimations of how the hydrogen escape rate evolved through Earth's history requires 3D chemistry-
climate models which include a global treatment of water vapour microphysics.
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All authors Gregory J. Cooke, Dan R. Marsh, Catherine Walsh, Felix Sainsbury-Martinez, Marrick Braam
Astrophysics of Galaxies
Footprints in the Wind: Probing X-ray Outflows in NGC 7469 using Near-Infrared Emission Lines
Léa M. Feuillet, Steve Kraemer, Anna Trindade Falcão et al. (+7 more)
AGN winds play an important role in the co-
evolution of supermassive black holes and their host
galaxies, yet their driving mechanisms and impact on
star formation remain subjects of active investigation. Critically, the lack of X-ray Integral Field Units currently limits our ability to acquire spatially resolved velocity information in the X-ray regime. However, instead, this can be achieved using the James Webb Space
Telescope. As part of an ongoing investigation of the
nuclear feedback processes in the nearby luminous AGN NGC 7469, we present an analysis of the kinematics of the X-ray emitting
outflows using near-infrared footprint lines such as [Mg VIII] 3.03 um. These high-ionization emission lines are associated with the same gas analyzed in the X-ray, and thus can be used to probe the footprint of the X-ray wind's velocity structure and ionization state. Thanks to the wide wavelength range available with JWST we also use nebular (e.g. [S IV] 10.51 um) and coronal (e.g. [Ne V] 14.32 um) emission lines to offer a comprehensive multi-phase view of the
outflows. We present mass and kinetic energy
outflow rates, and find that while the feedback processes in NGC 7469 are not efficient by theoretical
benchmarks, the most massive and energetic component is the high ionization X-ray gas.
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All authors Léa M. Feuillet, Steve Kraemer, Anna Trindade Falcão, Valentina Braito, Marcio Meléndez, Henrique R. Schmitt, James N. Reeves, Riccardo Middei, Travis C. Fischer, Mitchell Revalski
Astrophysics of Galaxies
Kinematics of Distant Milky Way Halo RR Lyrae Stars out to 160 kpc
Yuting Feng, Puragra Guhathakurta, Eric W. Peng et al. (+4 more)
We present a kinematical study of the outer
halo (r_GC approximately 60 to 160 kpc) of the Milky Way based on spectroscopy of 55 RR Lyrae
stars obtained with the ESI instrument on the Keck II
telescope. Our spectroscopic targets were selected from three photometric surveys: NGVS, DES, and Pan-STARRS1. We derive center-of-mass radial velocities with uncertainties of 6 to 35 km s^-1. The
halo velocity dispersion measured from our sample is 70 plus/minus 7 km s^-1. The velocity field shows a possible dipole-like structure, with redshifted northern and blueshifted southern hemispheres. Fitting a Milky Way - Large Magellanic Cloud dipole perturbation model yields a weak or marginal dipole signal with amplitude -30 (+16, -20) km s^-1 and apex direction (l, b) = (-38.2 (+42.4, -31.5), -41.3 (+27.9, -23.8)) deg, along with a bulk compression velocity of -16 plus/minus 11 km s^-1. Although limited by sky coverage and sample size, our results are consistent with the presence of LMC-induced disequilibrium in the distant
halo beyond 100 kpc. In addition to the 55 RR Lyrae
stars, our spectroscopy reveals that 10 additional photometrically selected RR Lyrae candidates are actually
quasar or blazar contaminants, highlighting the need for caution regarding such contaminants in sparsely sampled photometric surveys. Our study demonstrates that single-epoch spectroscopy of RR Lyrae
stars is a viable method for probing the kinematics of the outer
halo, and future surveys such as Rubin LSST and DESI-II have the potential to significantly advance this effort.
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All authors Yuting Feng, Puragra Guhathakurta, Eric W. Peng, Emily C. Cunningham, Patrick Côté, Laura Ferrarese, Stephen D. J. Gwyn
Earth and Planetary Astrophysics
Water versus land on temperate rocky planets
Claire Marie Guimond, Tilman Spohn, Svetlana Berdyugina et al. (+6 more)
Water and land surfaces on a
planet interact with gases in the atmosphere and with radiation from the
star. These interactions define the environments that prevail on the
planet, some of which may be more amenable to prebiotic chemistry, some to the
evolution of more complex life. This review article covers (i) the physical conditions that determine the ratio of land to sea on a rocky
planet, (ii) how this ratio would affect climatic and biologic processes, and (iii) whether future astronomical observations might constrain this ratio on
exoplanets. Water can be delivered in multiple ways to a growing rocky
planet – and although we may not agree on the contribution of different mechanism(s) to Earth's bulk water, hydrated building blocks and nebular ingassing could at least in principle supply several oceans' worth. The water that
planets sequester over eons in their solid deep mantles is limited by the water concentration at water saturation of nominally anhydrous mantle minerals, likely less than 2000 ppm of the
planet mass. Water is cycled between mantle and surface through outgassing and ingassing mechanisms that, while tightly linked to tectonics, do not necessarily require plate tectonics in every case. The actual water/land ratio at a given time emerges from the balance between the volume of surface water on the one hand, and on the other hand, the shape of the
planet (its ocean basin volume) that is carved out by dynamic topography, the petrologic
evolution of continents, impact cratering, and other surface-sculpting processes. By leveraging the contrast in reflectance properties of water and land surfaces, spatially resolved 2D maps of Earth-as-an-
exoplanet have been retrieved from models using real Earth observations, demonstrating that water/land ratios of rocky
exoplanets may be determined from data delivered by large-aperture, high-contrast imaging
telescopes in the future.
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All authors Claire Marie Guimond, Tilman Spohn, Svetlana Berdyugina, Paul K. Byrne, Nicolas Coltice, Donald M. Glaser, Manasvi Lingam, Charles H. Lineweaver, Peter A. Cawood
Astrophysics of Galaxies
Revisiting the X-ray-to-UV relation of Quasars in the era of all-sky surveys
Maria Chira, Antonis Georgakakis, Angel Ruiz et al. (+8 more)
The X-ray–to–UV relation of active
galactic nuclei (AGNs), commonly parametrized via the monochromatic luminosities at $2500\,\mathring{A}$ and $2\,keV$, reflects the energetic interplay between the
accretion disc and the X-ray-emitting corona, and is key for understanding
accretion physics. Previous studies suggest that disc-dominated emission becomes more prominent with increasing optical luminosity. However, the
redshift evolution of this relation remains debated, and a dependence on Eddington ratio, predicted by
accretion flow models, is still observationally unconstrained. We revisit this relation using a large, nearly all-sky sample by combining the SDSS DR16Q QSO catalogue with X-ray data from XMM-Newton and the SRG/eROSITA All-Sky Survey DR1, yielding 136,745 QSOs at
redshifts $0.5 \leq z < 3.0$. We introduce a hierarchical
Bayesian framework that treats X-ray detections and upper limits uniformly, enabling robust inference from both parametric and non-parametric models. We confirm a tight, sublinear $\log L_X({\rm 2\,keV})$-$\log L_{\nu}({\rm 2500\,\mathring{A}})$ correlation, but with a normalization at the lower end of previous estimates. Contrary to most literature results, we detect a mild but systematic
redshift evolution: the relation flattens and its intrinsic scatter decreases at higher
redshift. This trend is consistent with disc emission increasingly dominated by scattering and enhanced energy transfer to the X-ray corona, potentially indicating
redshift evolution in the X-ray bolometric correction. We find no significant dependence on Eddington ratio, in tension with recent
accretion flow models.
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All authors Maria Chira, Antonis Georgakakis, Angel Ruiz, Shi-Jiang Chen, Johannes Buchner, Amy L. Rankine, Elias Kammoun, Catarina Aydar, Mara Salvato, Andrea Merloni, Mirko Krumpe
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Reconciling ALP Dark Matter and Electroweak Baryogenesis through First-Order Electroweak Phase Transition
Dipendu Bhandari, Soumen Kumar Manna and Arunansu Sil
We show that an axionlike particle (ALP) can simultaneously generate the
baryon asymmetry and constitute dark matter through dynamics triggered by a first-order electroweak phase transition (EWPT). In our proposal, the transition briefly reshapes the ALP potential via a temperature-dependent
vacuum expectation value of a scalar field $S$, responsible for making the EWPT of first order, inducing a transient mass enhancement of ALP via higher-dimensional $U(1)$-breaking operator(s). This sudden kick generates a large ALP velocity near the onset of EWPT enabling the broadening of relic satisfied parameter space and predict a complementary
stochastic gravitational-wave signal from the underlying first-order transition. We further show that the same ALP dynamics can naturally fuel electroweak baryogenesis through its coupling to electroweak anomaly.
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Cosmology and Nongalactic Astrophysics
Adding electromagnetic birefringence to pulsar timing and astrometry to detect gravitational waves
Keisuke Inomata and Marc Kamionkowski
It was recently shown that the time variation of the polarization of electromagnetic waves from
pulsars can be used, in cross-correlation with
pulsar timing, to probe the chirality of an isotropic gravitational wave background. Here, we show that the expression for the cross-correlation is derived efficiently with the total-angular-momentum formalism and use this framework to extend the formulation to cross-correlation with astrometry. We do so for
spin-1 gravitational waves (that may arise in alternative-
gravity theories) as well as the general-relativistic
spin-2 gravitational waves.
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Solar and Stellar Astrophysics
Origin of the stellar Fe K{\alpha} line clarified with FUV and X-ray observations of a superflare on the RS Canum Venaticorum-type Star UX Arietis
Shun Inoue, Wataru Buz Iwakiri, Tomoki Kimura et al. (+11 more)
Fluorescence line diagnostics of the Fe K{\alpha} line at $\sim 6.4$ keV observed in both
solar and
stellar flares can constrain the latitude and size of the
flare loop, even in the absence of imaging observations. However, they are hampered by the unresolved origin of
stellar Fe K{\alpha} lines: i.e., it is unclear which of the two mechanisms-photoionization by hard X-ray
photons or collisional ionization by non-thermal electrons-is the dominant process. We present clear evidence for the photoionization origin based on simultaneous far ultraviolet (FUV) and soft X-ray observations of a superflare on the RS Canum Venaticorum-type
Star UX Arietis with Extreme ultraviolet spetrosCope for ExosphEric Dynamic (EXCEED; 900$-$1480 Å) onboard Hisaki and
Neutron Star Interior Composition Explorer (NICER; 0.2$-$12 keV). The
flare started at 22:50 UT on 2018 November 15 and released $2 \times 10^{36}$ erg in the 900$-$1480 Å band and $3 \times 10^{36}$ erg in the 0.3$-$4 keV band. The FUV emission, a proxy for non-thermal activity, peaked approximately 1.4 hours before the soft X-rays. In contrast, the Fe K{\alpha} line, detected at a statistical significance of $5.3 \sigma$ with an equivalent width of $67^{+28}_{-20}$ eV, peaked simultaneously with the thermal X-ray maximum rather than the non-thermal FUV peak-strongly supporting the photoionization hypothesis. Radiative transfer calculations, combined with the observed Fe K{\alpha} line intensity, further support the photoionization scenario and demonstrate the potential of this line to provide the
flare geometry.
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All authors Shun Inoue, Wataru Buz Iwakiri, Tomoki Kimura, Teruaki Enoto, Yuta Notsu, Hiroyuki Uchida, Kenji Hamaguchi, Shin Toriumi, Atsushi Yamazaki, Fuminori Tsuchiya, Go Murakami, Kazuo Yoshioka, Zaven Arzoumanian, Keith Gendreau