Instrumentation and Methods for Astrophysics
The Nucleated Atomistic Grain Growth Simulator (NAGGS): application to the size-dependent structural and physical properties of nanosilicate dust
Joan Mariñoso Guiu, Antoni Macià Escatllar and Stefan T. Bromley
We report the Nucleated Atomistic Grain Growth Simulator (NAGGS) as a new tool to model the growth of realistic nanosized
dust grains through the progressive
accretion of monomers onto a nucleated seed. NAGGS can be used with open source molecular dynamics codes, allowing for the modelling of grains that have different chemical compositions and are grown under a range of astrophysical conditions. To demonstrate how NAGGS works, we use it to produce 40 nanosilicate grain models with diameters of approx. 3.5 nm and consisting of approx. 1500 atoms. We consider Mg-rich olivinic and pyroxenic grains, and growth under two circumstellar
dust-producing conditions. We calculate properties from the atomistically detailed nanograin structures (e.g. morphology, surface area, density, dipole moments) with respect to the size, chemical composition, and growth temperature of the grains. Our simulations reveal detailed new insights into the complex interacting degrees of freedom during grain growth and how they affect the resultant physicochemical properties. For example, we find that surface roughness depends on the Mg:Si ratio during growth.We also find that nanosilicates have very high dipole moments, which depend on the growth temperature. Such findings could have important consequences (e.g. astrochemistry, microwave emission). In summary, our bottom-up physically motivated approach offers a detailed understanding of nanograins that could help in both interpreting observations and improving
dust models.
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Earth and Planetary Astrophysics
Detection of the 2021 Arid Meteor Shower on Maunakea, Hawai'i
Ichi Tanaka, Hitoshi Hasegawa, Toyokazu Uda et al. (+3 more)
We report the successful detection of the "Arid" Meteor Shower (IAU\#1130 ARD), predicted to emerge for the first time in 2021, using a publicly accessible YouTube live camera developed by us. This live camera, installed on the Subaru
Telescope dome in the summit region of Maunakea, Hawai'i, features a wide field of view (70 deg by 40 deg) and high sensitivity, capable of observing
stars fainter than 6th magnitude. Meteor detection was performed in two ways: visual inspection by citizen viewers and subsequent validation through automated detection. As a result, we confirmed that the number of meteors appearing from near the predicted radiant increased by more than six times (~9 sigma) compared to the preceding and following days. Our observation time was 4-5 hours after the predicted peak (
solar longitude = 193.9 deg), providing clear data indicating that the activity had not yet declined. Optical observations at this time from the Northern Hemisphere are extremely limited and unique, making our observation point valuable. The meteors are characterized as slow and faint appearance, but several brighter meteors with wakes were also observed. Simulations tracing the
dust trails from the parent body, Comet 15P/Finlay, suggest that our detection can be explained by either the
dust trails released in 2008 or 2014, both requiring high ejection velocities. However, during the comet's 2008 return, its activity was exceptionally quiet, making a high-velocity
dust ejection questionable. On the other hand, multiple large outbursts were observed during the 2014 return, at which time a certain amount of high-velocity
dust release is expected. We conclude that the
dust source of the meteor shower detected in Hawai'i this time is likely attributable to high-velocity (~67 m s-1)
dust ejected during the 2014 outburst.
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All authors Ichi Tanaka, Hitoshi Hasegawa, Toyokazu Uda, Mikiya Sato, Jun-ichi Watanabe, Masanobu Higashiyama
Solar and Stellar Astrophysics
Paving the Road to the Habitable Worlds Observatory with High-Resolution Imaging I: New and Archival Speckle Observations of Potential HWO Target Stars
Zachary D. Hartman, Catherine A. Clark, Michael B. Lund et al. (+15 more)
One of the key goals of the Habitable Worlds Observatory (HWO) is to directly image about 25 potentially habitable
exoplanets and determine their properties. This challenge will require a large survey of nearby, bright
stars – ~100 according to the Astro2020 Decadel Survey. To ensure the success of the mission and to help guide design decisions, the
stellar multiplicity of the target
stars must be well-understood. To this end, we present optical speckle imaging of
stars in the NASA
Exoplanet Exploration Program (ExEP) provisional HWO
star list, which is currently the Tier 1 target list for the HWO Target
Stars and Systems Sub-Working Group. We obtained new observations using `Alopeke and Zorro at Gemini Observatory and queried the
Exoplanet Follow-up Observing Program Archive for archival observations, resulting in speckle imaging data for 80 of the 164
stars. We confirmed one candidate companion detected previously by
Gaia (HD 90089) and obtained an ambiguous detection of a known companion (HD 212330). To examine our sensitivity to companions, we simulated
stellar companions down to ~0.1 $M_{\odot}$ for each target and found that 75%-85% would be detected in our speckle images; the remaining simulated companions are either too faint or too close-in, and will require follow-up using other methods such as long-term spectroscopic measurements and space-based techniques. This work represents a first step towards surveying potential HWO targets for close-in
stellar companions and helping to inform the target selection process for the HWO direct-imaging survey, bringing us closer towards the discovery of potential habitable worlds.
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All authors Zachary D. Hartman, Catherine A. Clark, Michael B. Lund, Kathryn V. Lester, José A. Caballero, Steve B. Howell, David Ciardi, Sarah Deveny, Mark E. Everett, Elise Furlan, Venu Kalari, Colin Littlefield, Andrew W. Stephens, Jennifer A. Burt, Guillaume Huber, Rachel Matson, Eric E. Mamajek, Noah Tuchow
Astrophysics of Galaxies
Rotational Kinematics in the Globular Cluster System of M31: Insights from Bayesian Inference
Yuan Li, Brendon J. Brewer, Geraint F. Lewis et al. (+1 more)
As ancient
stellar systems, globular clusters (GCs) offer valuable insights into the dynamical histories of large
galaxies. Previous studies of GC populations in the inner and outer regions of the Andromeda
Galaxy (M31) have revealed intriguing subpopulations with distinct kinematic properties. Here, we build upon earlier studies by employing
Bayesian modelling to investigate the kinematics of the combined inner and outer GC populations of M31. Given the heterogeneous nature of the data, we examine subpopulations defined by GCs'
metallicity and by associations with substructure, in order to characterise possible relationships between the inner and outer GC populations. We find that lower-
metallicity GCs and those linked to substructures exhibit a common, more rapid rotation, whose
alignment is distinct from that of higher-
metallicity and non-substructure GCs. Furthermore, the higher-
metallicity GCs rotate in
alignment with Andromeda's
stellar disk. These pronounced kinematic differences reinforce the idea that different subgroups of GCs were accreted to M31 at distinct epochs, shedding light on the complex assembly history of the
galaxy.
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All authors Yuan Li, Brendon J. Brewer, Geraint F. Lewis, Dougal Mackey
High Energy Astrophysical Phenomena
Superluminous supernovae: diverse rise times explain diverse spectra
Matt Nicholl
Type I superluminous
supernovae (SLSNe) are a diverse class of exceptionally bright massive
star explosions, which typically exhibit absorption from ionised oxygen in their early spectra. While their photometric properties (luminosity and duration) both span an order of magnitude, population studies suggest that these distributions are continuous. However, spectroscopic samples have shown some indications of distinct sub-types, either through similarity to certain prototype objects, or in terms of their velocity
evolution. Here we show that a well-observed SLSN, PTF12dam, completely changes its O II absorption profile as it rises to maximum light, moving from one proposed sub-type to another. This supports an interpretation where spectroscopic diversity is driven by the ejecta temperature at maximum light, rather than fundamental differences in the explosion or progenitor. Motivated by this, we develop a new diagnostic, the Brightness-Timescale-Temperature-Radius diagram, and a simple toy model for the
evolution of the photospheric velocity, to show that diversity in the light curve rise time (likely due to differences in ejected mass) naturally explains why SLSNe with broader light curves generally have weaker O II lines, lower photospheric velocities after maximum, and slower changes in photospheric velocity over time. We show that the velocity distribution of the known SLSN population favours a relatively flat ejecta density profile, consistent with a hot bubble inflated by a central engine.
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Astrophysics of Galaxies
The Column Density Probability Density Function of Cygnus-X
Yuchen Xing and Keping Qiu
The density distribution within molecular clouds offers critical insights into their underlying physical processes, which are essential for understanding
star formation. As a statistical measure of column density on the cloud scale, the shape and
evolution of the column density probability density function (N-PDF) serve as important tools for understanding the dynamics between
turbulence and
gravity. Here we investigate the N-PDFs of Cygnus-X using the column density map obtained from Herschel, supplemented by HI and Young
Stellar Objects (YSO) data. We find that the N-PDFs of Cygnus-X and four sub-regions display log-normal + power-law shapes, indicating the combined effects of
turbulence and
gravity in sculpting the density structure. We find evidence that the power-law segment of the N-PDFs flattens over time, and the transitional column density can be seen as a unique and stable
star formation threshold specific to each molecular cloud. These results not only clarify the physical state of Cygnus-X but also emphasize the utility of the N-PDF as a statistical diagnostic tool, as it is an accessible indicator of evolutionary stages and
star formation thresholds in molecular clouds.
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Solar and Stellar Astrophysics
Dispersive Properties of MHD Waves in the Expanding Solar Wind for a Parker Spiral Geometry
Sebastián Saldivia, Felipe Asenjo and Pablo S. Moya
In this work, we quantify the effects of
solar wind expansion on the dispersive properties of the three normal modes of ideal MHD using the Expanding Box Model, under a background
magnetic field that follows the Parker spiral geometry. From the linearized MHD-EBM equations, we construct the dispersion tensor and derive analytical expressions for the eigenfrequencies $\omega(k,R)$,
magnetic compressibility $C_B$, and the ratio of the parallel electric field to the perpendicular
magnetic field $|\delta E_\parallel|/|\delta B_\perp|$ of the magnetosonic modes to quantify how radial
solar wind expansion reshapes the character of compressive fluctuations in the
solar wind.
Magnetic compressibility increases with heliocentric distance, and this trend shows a better
alignment with in-situ observations when expansion is included from the MHD-EBM framework. $C_B$ shows a well-defined minimum at small radii and then increases linearly with distance, which naturally reproduces the observed transition from Alfvénic to compressive fluctuations between $\sim$0.3-1 AU. The ratio $|\delta E_\parallel|/|\delta B_\perp|$ reveals opposite behaviors for the fast and slow modes: while the fast mode becomes more electrostatic with increasing distance, the slow mode evolves to a more magnetically dominated character. Expansion reduces the growth of their electromagnetic/compressive balance at large radii. Our results demonstrate that
solar wind expansion actively redistributes energy between magnetically compressive modes and purely transverse fluctuations with respect to the background
magnetic field, playing a major role in shaping the radial
evolution of wave dynamics throughout the inner heliosphere.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Dipole Radiation and Kinetic Mixing from Dark Photon Solitons
Enrico D. Schiappacasse and Moira Venegas
Wave-like dark matter composed of
spin-1 particles, known as dark
photons, is theorized to form clumps called "vector
solitons". These
solitons are compact astrophysical objects that exhibit coherent oscillations and a high concentration relative to the local dark matter density. A significant portion of dark matter in
galactic halos today may consist of these
solitons. This study explores how
photons can be produced from these vector
solitons by the influence of external electromagnetic fields or charge densities, via a dimension-6 dark
photon-
photon coupling and a kinetic mixing, respectively. We further explore the astrophysical implications of these phenomena, highlighting a novel avenue for dark matter discovery that our research provides.
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Solar and Stellar Astrophysics
Featureless stars: Flux Calibration for Extremely Large Telescopes
Ryan Cooke, Nao Suzuki and J. Xavier Prochaska
The spectrophotometric flux calibration of recent spectroscopic surveys has reached a limiting systematic precision of approximately 1-3 percent, and is often biased near the wavelengths associated with H I Balmer absorption. As we prepare for the next generation of imaging and spectroscopic surveys, and high-precision cosmology experiments, we must find a way to address this systematic. Towards this goal, we have identified a global network of 29 bright (G < 17.5) featureless white
dwarf stars that have a spectral energy distribution consistent with an almost pure blackbody form over the entire optical and near-infrared wavelength range. Based on this sample, we have computed the systematic uncertainty and AB magnitude offsets associated with
Gaia, SDSS, SMSS, PanSTARRS, DES, and 2MASS, and we have also checked the consistency of our objects with both GALEX and WISE. The magnitude range of the featureless
stars reported here are ideally suited to observations taken with the forthcoming generation of extremely large
telescopes, as well as calibrating the survey data acquired by the Rubin, Euclid and Roman observatories. Finally, all of the high-precision spectrophotometric standard
stars reported here have been included in the latest release of the PypeIt data reduction pipeline.
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Astrophysics of Galaxies
Cosmic wallflowers: the circumgalactic origins of isolated ultra-compact star clusters at $z>7$
Floor van Donkelaar, Lucio Mayer, Pedro R. Capelo et al. (+2 more)
The discovery of gravitationally lensed
stellar clusters at high
redshift with the James Webb Space
Telescope (JWST) has revealed extremely compact, massive
star-forming systems in
galaxies at $z > 6$, providing a new window into early cluster formation. In this work, we investigate
star cluster formation in the circumgalactic environments of gas-rich
galaxies with
stellar masses spanning between $\sim$$10^{8}$ - $10^{11}$ M$_{\odot}$ at $z > 7$, using the MassiveBlackPS cosmological hydrodynamical simulation with 2 pc resolution. We identify 55
baryon-dominated clusters forming outside
galactic discs but within the virial radius of the primary
halo.
Star formation in these systems proceeds rapidly, reaching peak
stellar surface densities above $10^{5}$ M$_{\odot}$ pc$^{-2}$, closely matching the compact clusters recently discovered by JWST in the lensed
Cosmic Gems Arc at $z \approx 9.6$. Such extreme densities are a key pre-requisite to trigger runaway
stellar collisions, indicating that a subset of our clusters would be a likely host of intermediate-mass black holes (IMBHs). We find that massive
star clusters can form efficiently in the circumgalactic medium at early times through filament fragmentation, whereby high gas densities lead to rapid local collapse via a combination of thermal and gravitational instabilities. This formation pathway implies that some compact clusters formed in the quiet outskirts of forming
galaxies rather than within their discs. Small variations in filament properties, including
metallicity, density, and dark-matter content, influence the likelihood of a
star cluster being able to form an IMBH seed. The formation of clusters in circumgalactic environments points to a potential evolutionary pathway connecting early off-disc clusters, present-day globular clusters, and the seeds of massive BHs.
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All authors Floor van Donkelaar, Lucio Mayer, Pedro R. Capelo, Debora Sijacki, Angela Adamo
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Information-theoretic astrophysical uncertainties in the effective theory of dark matter direct detection
Gonzalo Herrera
The impact of astrophysical uncertainties in direct detection searches can vary significantly across particle dark matter models and detector targets, due to the different velocity and momentum dependencies of the scattering cross section. We address these uncertainties for all operators of the non-relativistic effective field theory of dark matter-nucleon interactions, making use of the Kullback-Leibler (KL) information divergence to measure the deviation of the true dark matter velocity distribution from the Maxwell-Boltzmann form. This approach quantifies how astrophysical uncertainties affect each operator in the effective theory, without assuming any specific functional form for the velocity distribution. While for some operators the uncertainties are smaller than one order of magnitude for entropically-motivated deviations from the Maxwell-Boltzmann form, for other operators these uncertainties can be as large as three orders of magnitude near threshold. Furthermore, we identify the dependence of the scattering rate for various operators of the effective theory with different velocity-weighted moments of the velocity distribution, functionally analogous to the mean, variance, or skewness. This provides new analytic insight into which features of the velocity distribution are most relevant to detect a given particle dark matter model. Our technique is general and could be applied to a broader class of physics problems where a physical observable depends on the statistical moments of an uncertain theoretical distribution.
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Cosmology and Nongalactic Astrophysics
Kinematic lensing with high-resolution spectroscopic surveys. A unique opportunity for transformative cosmology at high redshifts in the 2040s
Stefano Camera, Martin Kilbinger, Jean-Paul Kneib et al. (+10 more)
We present a science case to perform high-
redshift cosmic shear surveys for cosmology with next-generation spectroscopic instruments, such as the proposed MegaMapper and Wide-field Spectroscopic
Telescope. We argue that by using the novel technique called 'kinematic
lensing' (KL) it will be possible to obtain shear catalogues at
redshifts between 2 and 5. We show that the signal-to-noise ratio of KL at such high
redshifts is on average twice as much that expected from current weak
lensing (WL) surveys such as Euclid or LSST, and several times that of the previous generation of WL surveys like DES and KiDS, even with very conservative assumptions about the fraction of spectroscopically-detected sources for which KL shear estimates will be available. This will allow cosmologists to perform joint
galaxy clustering-
cosmic shear analyses over unprecedented
cosmic volumes and to probe the growth of structures deep in the matter-dominated era and across the onset of dark-energy domination, offering a unique opportunity to unveil the mystery of
cosmic acceleration.
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All authors Stefano Camera, Martin Kilbinger, Jean-Paul Kneib, Ofer Lahav, Giovanni Aricò, Sofia Contarini, Giulia Degni, Antonio Farina, Massimo Guidi, Vanshika Kansal, Federico Marulli, Alejandra Melo, Simone Sartori
Solar and Stellar Astrophysics
The gravitational stratification of multifluid and multispecies plasma
F. Zhang, J. Martínez-Sykora, Q. M. Wargnier et al. (+1 more)
Context. The
solar atmosphere is gravitationally stratified and consists of several layers at temperatures that vary by several orders of magnitude. Consequently, the
solar atmospheric
plasma changes from weakly ionized in the photosphere, partially ionized in the chromosphere, and to fully ionized in the corona. However, integrating ionization and recombination processes into multifluid
solar plasma models with gravitational stratification continues to be a nontrivial task. Aims. We intend to provide a method for constructing multifluid+multispecies (MFMS) gravitational stratification that satisfies the ionization
equilibrium and hydrostatic
equilibrium at the same time, avoiding causing nonphysical disturbances and numerical instability due to the initial imbalances. Methods. We assume that collisional interactions between fluids are sufficient for coupling all fluids when there is no high-frequency external driving force imposed. Ionization fractions can be (I) calculated assuming ionization in statistical
equilibrium at any given temperature or (II) extracted from other atmospheric models. A simple numerical integration routine would then be used to construct MFMS gravitational stratifications. Results. The gravitational stratification in hydrostatic
equilibrium can be constructed using the present numerical integration routine with any given ionization fractions of multispecies
plasmas. Meanwhile, without any dynamic driving force, fluid decoupling is initiated, particularly in the transition region of the constructed stratification, while the total velocity of all fluids remains at the level of zero. Conclusions. A gravitational stratification constructed using the present routine can be used in MFMS models to study specific dynamics without being affected by the initial imbalances.
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All authors F. Zhang, J. Martínez-Sykora, Q. M. Wargnier, V. H. Hansteen
Cosmology and Nongalactic Astrophysics
Probing General Relativity on Cosmological Scales in the 2040s
Federico Montano, Samantha J. Rossiter, Chris Addis et al. (+18 more)
General relativity is exquisitely tested in strong-field regimes, yet its validity on cosmological scales remains largely unexplored. Upcoming wide and deep large-scale structure surveys will access the ultra-large, linear scales where relativistic effects - Doppler terms, gravitational
redshift,
lensing magnification, and potential
evolution - leave significant imprints in the clustering of
galaxies. These signatures represent unique probes of spacetime that are inaccessible to standard Newtonian analyses but increasingly important as survey volumes grow. We outline the scientific potential of next-generation facilities, such as those envisioned within ESO's Expanding Horizons programme, to deliver the first robust measurements of relativistic effects in large-scale structure through multi-tracer power spectra and the single-tracer bispectrum of high-
redshift Lyman-break
galaxies. Detecting these contributions would open a new window on
gravity, enabling precision tests of general relativity and its alternatives on cosmological scales in the 2040s.
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All authors Federico Montano, Samantha J. Rossiter, Chris Addis, Jessie Hammond, Stefano Camera, Chris Clarkson, Mohamed Yousry Elkhashab, Massimo Guidi, Ofer Lahav, Giovanni Aricò, Sofia Contarini, Pratika Dayal, Giulia Degni, Antonio Farina, Vid Iršič, Federico Marulli, Elena Sarpa, Simone Sartori, Emiliano Sefusatti, Francesco Verdiani, Giovanni Verza
High Energy Astrophysical Phenomena
Accretion disc winds in X-ray binaries
Teo Muñoz-Darias, María Díaz Trigo, Chris Done et al. (+2 more)
Despite early theoretical expectations that large-scale, massive
outflows would be triggered by
accretion onto black holes and
neutron stars, their presence was not firmly established until the 2000s. Since then, these
accretion disc winds have been recognised as a common, perhaps ubiquitous, feature of
accretion discs in X-ray binaries. Over the past two decades, our understanding of these
outflows has expanded significantly, with their associated phenomenology now observed across the X-ray, ultraviolet, optical, and near-infrared regimes. In this review, we provide a comprehensive summary of the observational properties of both low- and high-ionisation winds, treating each separately as well as part of a broader phenomenon, and place these findings in the context of current theoretical modelling. We discuss their close connection with disc atmospheres, their impact on the
accretion process, and their role within the broader framework that includes the
radio jet and the different
accretion flow configurations and states. We also address current challenges and outline some of the anticipated developments, particularly those linked to upcoming observational facilities.
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All authors Teo Muñoz-Darias, María Díaz Trigo, Chris Done, Gabriele Ponti, Ryota Tomaru
Solar and Stellar Astrophysics
The fate of the failed supernova candidate M31-2014-DS1
Emma R. Beasor, Nathan Smith, Jeniveve Pearson et al. (+4 more)
The fate of massive
stars above 20M$_{\odot}$ remains uncertain. Debate persists about whether they die as
supernovae (SNe), or if they collapse directly into black holes (BHs) with little or no optical outburst – so-called “failed
supernovae”. The source M31-2014-DS1 experienced an optical outburst in 2014 and has remained faint at visual wavelengths since then. Due to its persistent faintness, it has been proposed as a failed SN candidate. We present new observations of this candidate obtained using the James Webb Space
Telescope (JWST), the Submillimeter Array (SMA), and Chandra. The JWST observations demonstrate that a luminous mid-infrared source persists at the same location a decade after the
star faded at visual wavelengths. We model its current spectral energy distribution (SED) as a
dust-enshrouded
star. No X-ray emission is detected, disfavoring the hypothesis that the late-time luminosity is powered by
accretion onto a BH. We find that the remaining source is highly obscured by an asymmetric distribution of circumstellar
dust, making it difficult to quantify its physical properties using spherically symmetric radiative transfer codes. The
dust geometry requires that the inferred bolometric luminosity is only a lower limit, as a significant fraction of the central source's radiation may escape without being reprocessed by
dust. We discuss the implications of these findings in the context of failed SN models and consider the potential overlap with signatures expected from a
stellar merger, which also seems to provide a plausible explanation of this source.
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All authors Emma R. Beasor, Nathan Smith, Jeniveve Pearson, Bhagya Subrayan, Edo Berger, David J. Sand, Jay Strader
Astrophysics of Galaxies
Revised AGN Spectral Model Reveals a More Significant Role in Cosmic Reionization
Tong Su, Qi Guo, Wenxiang Pei et al. (+1 more)
Reionization marks one of the most important phase transitions in the history of the Universe, during which neutral baryonic matter was transformed into ionized
plasma. While
star-forming
galaxies are widely regarded as the primary drivers of this process, the extent to which active
galactic nuclei (AGNs) contribute remains a subject of ongoing investigation. In this study, we integrate a physically motivated AGN spectral energy distribution (SED) model with state-of-the-art observations to reassess the contribution of AGNs to
cosmic reionization. Our findings indicate that adopting a more sophisticated AGN SED model could substantially increase the predicted ionizing
photon output by a factor of 3$\sim$4, elevating AGNs to a more significant role ($\approx$20%) in maintaining reionization than previously estimated. The inclusion of abundant faint AGNs further amplifies this contribution by a factor of a few. These conclusions remain robust across a wide range of
accretion rates and ionizing
photon escape fractions. Collectively, our results suggest that AGNs may have played a more prominent and previously underestimated role in the reionization of the Universe.
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All authors Tong Su, Qi Guo, Wenxiang Pei, Linhua Jiang
Astrophysics of Galaxies
Modeling the Milky Way wind: Supernova-driven outflows accelerate HI clouds near the Galactic center
Andrea Afruni, Enrico M. Di Teodoro, Lucia Armillotta et al. (+2 more)
Multiwavelength observations, from
radio to X-rays, have revealed the presence of multiphase high-velocity gas near the center of the Milky Way likely associated with powerful
galactic outflows. This region offers a unique laboratory to study the physics of feedback and the nature of multiphase winds in detail. To this end, we have developed physically motivated semi-analytical models of a multiphase
outflow consisting of a hot gas phase ($T \gg 10^6$ K) that embeds colder clouds ($T \sim 5000$ K). Our models include the gravitational potential of the Milky Way; the drag force exerted by the hot phase onto the cold clouds; and the exchange of mass, momentum, and energy between gas phases. Using
Bayesian inference, we compared the predictions of our models with observations of a population of HI high-velocity clouds detected up to $\sim$1.5 kpc above the
Galactic plane near the
Galactic center. We find that a class of
supernova-driven winds launched by
star formation in the central molecular zone can successfully reproduce the observed velocities, spatial distribution, and masses of the clouds. In our two-phase models, the mass and energy loading factors of both phases are consistent with recent theoretical expectations. The cold clouds are accelerated by the hot wind via ram pressure drag and via
accretion of high-velocity material, resulting from the turbulent mixing and subsequent cooling. However, this interaction also leads to gradual cloud disruption, with smaller clouds losing over 70% of their initial mass by the time they reach $\sim$2 kpc.
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All authors Andrea Afruni, Enrico M. Di Teodoro, Lucia Armillotta, Callum A. Lynn, Naomi M. McClure-Griffiths
Solar and Stellar Astrophysics
Overestimated Pressure Broadening Misleads Model Spectra in Cool M Dwarf Stars
Ana Glidden, Veronika Witzke, Alexander I. Shapiro et al. (+1 more)
Available one-dimensional
stellar models fail to reproduce the observed spectrum of the ultracool M
dwarf TRAPPIST-1. In particular, current models predict strong iron hydride (FeH) absorption due to the Wing-Ford bands at 0.99$\mu$m, yet this spectral feature is only weakly present in TRAPPIST-1 and other mid-to-late M
dwarf stars. Additionally, the shape of the continuum between the water bands in the near-infrared does not match between models and observations. Here, we show that assumptions about pressure broadening, specifically van der Waals broadening, have a dramatic effect on modeled broadband spectral features. We use Merged Parallelized Simplified-ATLAS to generate synthetic spectra over a range of van der Waals broadening strengths, adopting 1D PHOENIX temperature-pressure structures. We find that minimal broadening best matches the observed FeH profile at 0.99$\mu$m and in the pseudocontinuum between the large water bands. These results suggest that broadening prescriptions derived for Sun-like
stars are not valid for lower-mass
stars and that pressure broadening for molecular lines in cool
stellar atmospheres must be reevaluated. Refining pressure broadening treatments will improve the accuracy of M
dwarf spectral models, enabling more reliable determinations of
stellar properties and atmospheric compositions of
planets orbiting M
dwarfs.
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All authors Ana Glidden, Veronika Witzke, Alexander I. Shapiro, Sara Seager
Astrophysics of Galaxies
Interaction of the central jet with the surrounding gas in the protostellar outflow from IRAS 04166+2706
M. Tafalla, D. Johnstone, J. Santiago-Garcia et al. (+3 more)
$Context.$ The
outflow from the Class 0 protostar IRAS 04166+2706 (hereafter IRAS 04166) contains a remarkably symmetric jet-like component of extremely high-velocity (EHV) gas. $Aims.$ We studied the IRAS 04166
outflow and investigated the relation between its EHV component and the slower
outflow gas. $Methods.$ We mosaicked the CO(2–1) emission from the IRAS 04166
outflow using the 12m and the Compact Arrays of ALMA. We also developed a ballistic toy model of the gas ejected laterally from a jet to interpret the data. $Results.$ In agreement with previous observations, the ALMA data show that the slow
outflow component is distributed in two opposed conical lobes and has a shear-flow pattern with velocity increasing toward the axis. The EHV gas consists of a series of arc-like condensations that span the full width of the conical lobes and merge with their walls, suggesting that the fast and slow
outflow components are physically connected. In addition, position–velocity diagrams along the
outflow axis show finger-like extensions that connect the EHV emission with the origin of the diagram, as if part of the EHV gas had been decelerated by its interaction with the low-velocity
outflow. A ballistic model can reproduce these finger-like extensions assuming that the EHV gas consists of jet material that has been ejected laterally over a short period of time and has transferred part of its momentum to the surrounding shear flow. $Conclusions.$ The EHV gas in the IRAS 04166
outflow seems to play a role in the acceleration of the slower gas component. The presence of similar finger-like extensions in the position-velocity diagrams of other
outflows suggests that this process may be occurring in other systems, even if the EHV component is not seen because it has an atomic composition.
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All authors M. Tafalla, D. Johnstone, J. Santiago-Garcia, Q. Zhang, H. Shang, C.-F. Lee
Astrophysics of Galaxies
Unveiling the 3D structure of the central molecular zone from stellar kinematics and photometry: The 50 and 20 km/s clouds
Francisco Nogueras-Lara, Ashley T. Barnes, Jonathan D. Henshaw et al. (+25 more)
The central molecular zone (CMZ), surrounding the
Galactic centre, is the largest reservoir of dense molecular gas in the
Galaxy. Despite its relative proximity, the 3D structure of the CMZ remains poorly constrained, primarily due to projection effects. We aim to constrain the line-of-sight location of two molecular clouds in the CMZ – the 50 and 20 km/s clouds – and to investigate their possible physical connection using
stellar kinematics and photometry. This study serves as a pilot for future applications across the full CMZ. We estimated the line-of-sight position of the clouds by analysing
stellar kinematics,
stellar densities, and
stellar populations towards the cloud regions and a control field. We find an absence of westward moving
stars in the cloud regions, which indicates that they lie on the near side of the CMZ. This interpretation is supported by the
stellar density distributions. The similar behaviour observed in the two clouds, as well as in the region between them (the ridge), suggests that they are located at comparable distances and are physically linked. We also identified an intermediate-age
stellar population (2-7 Gyr) in both regions, consistent with that observed on the near side of the CMZ. We estimated the line-of-sight distances at which the clouds and the ridge become kinematically detectable (i.e. where the proper motion component parallel to the
Galactic plane differs from that of the control field at the 3 sigma level) by converting their measured proper motions parallel to the
Galactic plane using a theoretical model of the
stellar distribution. We find that the 50 and 20 km/s clouds are located at $43\pm8$ pc and $56\pm11$ pc from Sgr A*, respectively, and that the ridge lies at $56\pm11$ pc; this supports the idea that the clouds are physically connected through the ridge.
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All authors Francisco Nogueras-Lara, Ashley T. Barnes, Jonathan D. Henshaw, Karl Fiteni, Yoshiaki Sofue, Rainer Schödel, Álvaro Martínez-Arranz, Mattia C. Sormani, Jairo Armijos-Abendaño, Laura Colzi, Izaskun Jiménez-Serra, Víctor M. Rivilla, Pablo García, Adam Ginsburg, Yue Hu, Ralf S. Klessen, J. M. Diederik Kruijssen, Volker Tolls, Alex Lazarian, Dani R. Lipman, Steven N. Longmore, Xing Lu, Sergio Martín, Denise Riquelme-Vásquez, Jaime E. Pineda, Álvaro Sánchez-Monge, Arianna Vasini, Elisabeth A.C. Mills
Cosmology and Nongalactic Astrophysics
Mimicking Phantom Dark Energy with Evolving Dark Matter Mass
Lorenzo La Penna, Alessio Notari and Michele Redi
We present a general method to reproduce a given cosmological background through energy exchange between dark energy (DE) and dark matter (DM). This can be simply realized with a standard quintessence scalar field that controls the DM mass. In particular a background with phantom crossing can be effectively realized without introducing ghosts or other pathologies. For example one can reproduce exactly the background that gives the best fit to the recent DESI+CMB+DESY5 data, within the Chevallier-Polarski-Linder (CPL) parametrization of DE. Although the background
evolution is identical, the perturbations differ, leading to modified growth of structures. If the DM mass varies at late times, early-time observables are not modified and can reproduce the main predictions of the target model, but late-time observables are affected. We discuss in particular the effects on the matter power spectrum, CMB
lensing and ISW effect. When reproducing the best fit CPL background model, this scenario generically predicts $\mathcal{O}(10\%)$ deviations in such observables. However, for suitable choices of parameters, effects on the matter power spectrum can be smaller, motivating a detailed study. In general, energy exchange between DE and DM generates a mismatch between the matter power spectrum and the gravitational potential amplitudes compared to the decoupled case, that can lead to deviations observable in future experiments.
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Instrumentation and Methods for Astrophysics
Three-dimensional scene reconstruction using Roman slitless spectra
Tri L. Astraatmadja, Andrew S. Fruchter, Susana E. Deustua et al. (+10 more)
The Nancy Grace Roman Space
Telescope will carry out a wide-field imaging and slitless spectroscopic survey of Type Ia
Supernovae to improve our understanding of dark energy. Crucial to this endeavor is obtaining
supernova spectra uncontaminated by light from their host
galaxies. However, obtaining such spectra is made more difficult by the inherent problem in wide-field slitless spectroscopic surveys: the blending of spectra of close objects. The spectrum of a
supernova will blend with the host
galaxy, even from regions distant from the
supernova on the sky. If not properly removed, this contamination will introduce systematic bias when the
supernova spectra are later used to determine intrinsic
supernova parameters and to infer the parameters of dark energy. To address this problem we developed an
algorithm that makes use of the spectroscopic observations of the host
galaxy at all available observatory roll angles to reconstruct a three-dimensional (3d; 2d spatial, 1d spectral) representation of the underlying host
galaxy that accurately matches the 2d slitless spectrum of the host
galaxy when projected to an arbitrary rotation angle. We call this “scene reconstruction”. The projection of the reconstructed scene can be subtracted from an observation of a
supernova to remove the contamination from the underlying host. Using simulated Roman data, we show that our method has extremely small systematic errors and significantly less random noise than if we subtracted a single perfectly aligned spectrum of the host obtained before or after the
supernova was visible.
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All authors Tri L. Astraatmadja, Andrew S. Fruchter, Susana E. Deustua, Helen Qu, Masao Sako, Russell E. Ryan Jr., Yannick Copin, Greg Aldering, Rebekah A. Hounsell, David Rubin, Lluís Galbany, Saul Perlmutter, Benjamin M. Rose
Cosmology and Nongalactic Astrophysics
Mitigating Simulator Dependence in AI Parameter Inference for the Epoch of Reionization: The Importance of Simulation Diversity
Jasper Solt, Jonathan C. Pober and Stephen H. Bach
The 21cm signal of neutral hydrogen contains a wealth of information about the poorly constrained era of cosmological history, the Epoch of Reionization (EoR). Recently, AI models trained on EoR simulations have gained significant
attention as a powerful and flexible option for inferring parameters from 21cm observations. However, previous works show that AI models trained on data from one simulator fail to generalize to data from another, raising doubts about AI models' ability to accurately infer parameters from observation. We develop a new strategy for training AI models on cosmological simulations based on the principle that increasing the diversity of the training
dataset improves model robustness by averaging out spurious and contradictory information. We train AI models on data from different combinations of four simulators, then compare the models' performance when predicting on data from held-out simulators acting as proxies for the real universe. We find that models trained on data from multiple simulators perform better on data from a held-out simulator than models trained on data from a single simulator, indicating that increasing the diversity of the training
dataset improves a model's ability to generalize. This result suggests that future EoR parameter inference methods can mitigate simulator-specific bias by incorporating multiple simulation approaches into their analyses.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Towards a unified quantum field theory of dark energy and inflation: unstable de Sitter vacuum and running vacuum
Joan Solà Peracaula, Àlex González-Fuentes and Cristian Moreno-Pulido
Inflation is a necessary
cosmic mechanism to cure basic inconsistencies of the standard model of cosmology. These problems are usually `fixed' by postulating the existence of a scalar field (called the “inflaton”). However, other less ad hoc options are possible. In the running
vacuum model (RVM) framework, the
vacuum energy density (VED) $\rho_{\rm vac}$ is a function of the Hubble rate $H$ and its time derivatives. In this context, the VED is dynamical (there is no rigid cosmological constant $\Lambda$). In the FLRW epoch, $\rho_{\rm vac}$ evolves very slowly with expansion. In contrast, in the very early universe the
vacuum fluctuations induce higher powers $H^N$ capable of unleashing fast inflation in a short period in which $H\simeq$ const. We call this mechanism `RVM-inflation'. It does not require an inflaton field since inflation is brought about by pure
quantum field theory (QFT) effects on the dynamical background. It is different from Starobinsky's inflation, in which $H$ is never constant. In this work, we study a closely related scenario: the decay of the exact de Sitter
vacuum into FLRW spacetime in its radiation epoch and the subsequent impact on the current universe, and compare with the RVM. We find that in both cases inflation is driven by $H^4$ powers together with subleading contributions of order $H^2$ that ease a graceful-exit transition into the radiation-dominated epoch, where the FLRW regime starts and ultimately develops a mildly evolving VED in the late universe: $\delta\rho_{\rm vac}\sim {\cal O}(m_{\rm Pl} ^2 H^2)$. The proposal presented here aims at a unified QFT approach to inflation and dark energy (conceived as dynamical
vacuum energy) with potentially measurable phenomenological consequences in the present universe, and constitutes a first step toward establishing its full theoretical and phenomenological consistency.
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Solar and Stellar Astrophysics
Addressing Known Challenges in Solar Flare Forecasting I: Limb-Flare Prediction with a 4-pi Full-Heliosphere Framework
K.D. Leka, Eric L. Wagner, Lisa Upton et al. (+3 more)
A demonstrated failure mode for operational
solar flare forecasting is the inability to forecast
flares that occur near, or just beyond, the
solar limb. To address this shortcoming, we develop a "4pi" full-heliosphere event
forecasting framework and evaluate its statistical classification ability against this specific challenge. A
magnetic surface flux transport model is used to generate full-sun maps of the photospheric radial
magnetic field from which active regions (ARs) are identified and tracked using a new labeling scheme that is observer-location agnostic and allows for post-facto modifications.
Flare-relevant
magnetic parameters couple to a "visibility" index that specifies AR location relative to the visible
solar limb and expected
flare detection.
Flare labels are assigned according to peak Soft X-ray flux, and a statistical classification is performed using nonparametric discriminant analysis. A version where new or emerging ARs on the far ("invisible" side of the Sun are incorporated into the model by way of far-side helioseismology, is also tested. We evaluate the new framework by its performance specifically including the limb areas using Brier Skill Score and ROC Skill Score, finding improvement at the 2-sigma level or less. However, we do find that the number of False Negatives, or "missed" forecasts decreases, and find strong evidence that the additional information provided by the far-side helioseismology can help predict near- and just-beyond-limb
flares, particularly for East-limb events. While individual components of this framework could be improved, we demonstrate that a known failure mode for
solar flare forecasting can be mitigated with available resources.
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All authors K.D. Leka, Eric L. Wagner, Lisa Upton, Bibhuti Kumar Jha, Kiran Jain, Sara Petty
High Energy Astrophysical Phenomena · Cross-listed from hep-th
Extended Heun Hierarchy in Quantum Seiberg-Witten Geometry
Peng Yang, Yi-Rong Wang and Kilar Zhang
We investigate the
quantum geometry of the Seiberg-Witten curve for $\mathcal{N}=2$, $\mathrm{SU(2)}^n$ linear quiver gauge theories. By applying the Weyl quantization prescription to the algebraic curve, we derive the corresponding second-order differential equation and demonstrate that it is isomorphic to the Extended Heun Equation with $n+3$ regular singular points. The physical parameters of the gauge theory are linked to the canonical coefficients of the Heun equation via a
polynomial representation of the Seiberg-Witten curve. This framework provides the necessary mathematical foundation to apply non-perturbative gauge-theoretic techniques, such as instanton counting, to spectral problems in gravitational physics, most notably for higher-dimensional black holes.
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Cosmology and Nongalactic Astrophysics
Symbolically regressing dark matter halo profiles using weak lensing
Alicia Martín, Tariq Yasin, Deaglan J. Bartlett et al. (+2 more)
The structure of dark matter
haloes is often described by radial density profiles motivated by cosmological simulations. These are typically assumed to have a fixed functional form (e.g. NFW), with some free parameters that can be constrained with observations. However, relying on simulations has the disadvantage that the resulting profiles depend on the dark matter model and the baryonic physics implementation, which are highly uncertain. Instead, we present a method to constrain
halo density profiles directly from observations. This is done using a symbolic regression
algorithm called Exhaustive Symbolic Regression (ESR). ESR searches for the optimal analytic expression to fit data, combining both accuracy and simplicity. We apply ESR to a sample of 149
galaxy clusters from the HSC-XXL survey to identify which functional forms perform best across the entire sample of clusters. We identify density profiles that statistically outperform NFW under a minimum-description-length criterion. Within the radial range probed by the weak-
lensing data ($R \sim 0.3 - 3$ h$^{-1}$ Mpc), the highest-ranked ESR profiles exhibit shallow inner behaviour and a maximum in the density profile. As a practical application, we show how the best-fitting ESR models can be used to obtain enclosed mass estimates. We find masses that are, on average, higher than those derived using NFW, highlighting a source of potential bias when assuming the wrong density profile. These results have important knock-on effects for analyses that utilise clusters, for example cosmological constraints on $\sigma_8$ and $\Omega_m$ from cluster abundance and clustering. Beyond the HSC
dataset, the method is readily applicable to any data constraining the dark matter distribution in
galaxies and
galaxy clusters, such as other weak
lensing surveys,
galactic rotation curves, or complementary probes.
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All authors Alicia Martín, Tariq Yasin, Deaglan J. Bartlett, Harry Desmond, Pedro G. Ferreira
Instrumentation and Methods for Astrophysics · Cross-listed from physics.plasm-ph
Machine learning for radiative hydrodynamics in astrophysics
Gonzague Radureau
Radiation hydrodynamics describes the interaction between high-temperature hypersonic
plasmas and the radiation they emit or absorb, a coupling that plays a central role in many astrophysical phenomena related to
accretion and ejection processes. The HADES code was developed to model such systems by coupling hydrodynamics with M1-gray or M1-multigroup radiative transfer models, which are well suited to optically intermediate media. Despite its accuracy, radiation hydrodynamics simulations remain extremely demanding in terms of computational cost. Two main limitations are responsible for this. First, the M1-multigroup model relies on a closure relation with no analytic expression, requiring expensive numerical evaluations. Second, the Courant-Friedrichs-Lewy condition strongly restricts the time step of the explicit schemes used in HADES. To overcome these difficulties, two complementary Artificial Intelligence based strategies were developed in this thesis. The first approach consists in training a Multi-Layer Perceptron to approximate the M1-multigroup closure relation. This method achieves excellent accuracy while reducing the computational cost by a factor of 3000, making it the most efficient approach currently available for this task. This performance gain enables high-fidelity simulations of radiative shocks, in which radiation directly influences the shock structure. In particular, increasing spectral resolution slows down the shock and enlarges the radiative precursor. The second approach explores the use of Physics-Informed Neural Networks to directly solve the radiation hydrodynamics equations and extrapolate simulations beyond their initial time range. Tests on purely hydrodynamic shocks show accurate handling of discontinuities, but application to radiative shocks remains challenging and requires further investigation.
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Cosmology and Nongalactic Astrophysics
How deep can a cosmic void be? Voids-informed theoretical bounds in Galileon gravity
Tommaso Moretti, Noemi Frusciante, Giovanni Verza et al. (+1 more)
We establish a void-based consistency test for Galileon scalar-tensor theories. We show that the previously reported unphysical breakdown of the predicted Newtonian force in certain Galileon models is controlled by a single condition linking non-linear void dynamics to the
cosmic expansion history. This connection yields a
redshift-dependent upper bound on the allowed depth of voids and promotes this requirement to a new viability condition, complementary to standard stability criteria. As an example, we apply this void-based criterion to a linear parameterization in the scale factor constrained by theoretical and observational bounds; we find that $\sim 60\%$ of the parameter space is excluded, with most problematic models failing by $z\lesssim 10$. These results position
cosmic voids as sharp, complementary and theory-informed filters for viable modified
gravity, enabling more informed priors and parameter-space choices in future cosmological inference.
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All authors Tommaso Moretti, Noemi Frusciante, Giovanni Verza, Francesco Pace