Instrumentation and Methods for Astrophysics
Comment on 'Color astrophotography with a 100 mm-diameter f/2 polymer flat lens', Appl. Phys. Lett. 126, 051701 (2025)
G. K. Skinner and J. F. Krizmanic
It is argued that the lens described in the paper commented upon has a focussing efficiency of less than 0.03% and an angular resolution for broadband radiation that is an order of magnitude worse that the diffraction limit. Furthermore incident radiation that is not focussed will lead to background fog in the image plane.
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High Energy Astrophysical Phenomena
No Pulsar Detected in Reprocessed Archival Parkes Observations of SNR 1987A
Fronefield Crawford and Haoyang Xu
We have reprocessed the available archival
radio pulsar search observations of SNR 1987A taken with the Parkes 64-m
telescope, some of which have not been previously published. We conducted a standard periodicity search on these data as well as a single pulse search at a range of dispersion measures. We found no convincing candidate signals, and we calculate flux density, luminosity, and single pulse fluence limits from these observations. The derived luminosity limits are comparable to the luminosities of three young, energetic
pulsars (the Crab
pulsar, PSR B0540$-$69, and PSR J0537$-$6910), and so we cannot rule out the existence of a
pulsar in SNR 1987A with a similar
radio luminosity.
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Cosmology and Nongalactic Astrophysics
Controlled Ensemble Null Tests of Dynamical Dark Energy Hints: Single-Probe Recovery of $\Lambda$CDM with BAO, Compressed-CMB, and SNe Mocks
Seokcheon Lee
Recent combined cosmological analyses have reported mild apparent departures from the cosmological-constant equation of state. We perform controlled ensemble null tests using observable-level Gaussian BAO-like, compressed-CMB-like, and Type Ia
supernova-like mock
datasets generated from a common fiducial flat $\Lambda$CDM cosmology. The aim is to determine whether each constituent single-probe likelihood can produce an apparent dynamical-dark-energy (DDE)-like marginalized-posterior displacement, or spuriously exclude the fiducial model, through its own degeneracy structure and calibration freedom. We adopt probe-adapted parameterizations for the BAO scale, CMB physical matter density, and
supernova normalization degeneracy, together with explicit convergence diagnostics, posterior-coverage tests, and realization-level pull statistics. None of the three single-probe analyses spuriously excludes the fiducial input at the 95% level. All completed BAO and SNe chains enter their final ensembles after adaptive extension of initially rejected runs; for compressed CMB, a mock-data-space audit finds no detectable selection dependence within the sensitivity of the 208-mock ensemble. The compressed-CMB-only likelihood nevertheless exhibits stable displaced marginalized medians together with broad late-time posterior intervals, illustrating that posterior location and model exclusion are distinct diagnostics. These results show that a displaced marginalized posterior in a single realization is not, by itself, evidence for dynamical dark energy. Such shifts should be interpreted through mock-ensemble recovery, convergence diagnostics, and the probe-dependent geometry of the likelihood.
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Cosmology and Nongalactic Astrophysics
Effects of New Forces on Scalar Dark Matter Solitons
Alize Sucsuzer, Mark P. Hertzberg and Michiru Uwabo-Niibo
New long range forces acting on ordinary matter are highly constrained. However it is possible such forces act on dark matter, as it is less constrained observationally. In this work, we consider dark matter to be made of light
bosons, such as
axions. We introduce a mediator that communicates a new force between dark matter particles, in addition to
gravity. The mediator is taken to be light, but not massless, so that it can affect small scale
galactic behavior, but not current cosmological behavior. As a concrete application of this idea, we analyze the effects on scalar dark matter
solitons bound by gravitation, i.e.,
boson stars, which have been claimed to potentially provide cores of
galaxies. We numerically determine the
soliton's profiles in the presence of this new force. We also extend the analysis to multiple mediators. We show that this new force alters the relation between core density and core radius in a way that can provide improvement in fitting data to observed
galactic cores, but for couplings of order the gravitational strength, the improvement is only modest.
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Solar and Stellar Astrophysics
Natalia de Jesús Baz-Pérez, Dany Page, Simon Guichandut et al. (+3 more)
We model early
accretion of light elements, He, C, and O, onto a new-born
neutron star using the public
stellar evolution code MESA, simulating what may happen during the first few years of its life. We find that, under the appropriate conditions, significant amounts of these elements can be accreted up to densities of 10^9 g/cc without triggering a
nuclear explosion that would convert them into heavy elements. These results help to understand observations that favor light elements in the atmospheres of young cooling
neutron stars, as the one found in the
supernova remnant Cassiopeia A, and also add support to the recent indications for the presence of a
neutron star, NS 1987A, in the remnant of SN 1987A.
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All authors Natalia de Jesús Baz-Pérez, Dany Page, Simon Guichandut, Martin Nava-Callejas, Yuri Cavecchi, Andrew Cumming
Earth and Planetary Astrophysics
Helium Depletion in Escaping Atmospheres of Sub-Neptunes: A Signature of Primary-to-Secondary Transition
Issei Kobayashi, Hiroyuki Kurokawa, Laura Schaefer et al. (+1 more)
Short-period sub-Neptunes are common in extrasolar systems. These sub-Neptunes are generally thought to have primary atmospheres of protoplanetary-disk gas origin. However, atmospheric escape followed by degassing from their interiors can lead to the transition to secondary atmospheres depleted in gases less-soluble to magma, such as helium. These primary and secondary atmospheres can potentially be distinguished from observations of escaping hydrogen and helium. This study aims to elucidate the impact of the primary-secondary transition on atmospheric compositions of short-period sub-Neptunes. We simulate their
evolution with atmospheric escape driven by
stellar X-ray and extreme ultraviolet irradiation and degassing of hydrogen, helium, and water from their rocky interiors, with a one-dimensional structure model. We show that the transition takes place for low-mass, close-in
planets which experience extensive atmospheric escape. These
planets show the depletion of helium and enrichment of water in their atmospheres, because of their low and high abundances in the planetary interiors, respectively. A compilation of our parameter survey (the orbital period, planetary mass, envelope mass, and mantle FeO content) shows a correlation between the
planet radius and the helium escape rate. We suggest that the transition from primary to secondary atmospheres may serve an explanation for helium non-detection for relatively-small ($\lesssim 2.5\ R_\oplus$)
exoplanets.
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All authors Issei Kobayashi, Hiroyuki Kurokawa, Laura Schaefer, Satoshi Okuzumi
Astrophysics of Galaxies
CLASSY XIII. Cutting through the Clouds - Comparing Indirect Tracers of Ionizing Photon Escape
Kaelee S. Parker, Danielle A. Berg, John Chisholm et al. (+25 more)
The Epoch of Reionization (EoR) provides critical insights into the role of early
galaxies in shaping the ionization state of the universe. However, because of the opacity of the intergalactic medium, it is often not possible to make direct measurements of the ionizing
photon escape fraction ($f_{\mathrm{esc}}^{\: \mathrm{LyC}}$) of high-
redshift ($z \gtrsim 4$)
galaxies. To explore the agreement and systematics of common indirect approaches, we applied six empirically calibrated diagnostics to predict $f_{\mathrm{esc}}^{\: \mathrm{LyC}}$ for the 45 nearby
star-forming
galaxies from the COS Legacy Spectroscopic SurveY (CLASSY). These methods- based on ultraviolet (UV) absorption lines, the UV continuum slope, Ly$\alpha$ kinematics, a multivariate model, radiation-hydrodynamic simulations, and nebular emission line ratios- enable us to explore systematic differences between predictions and assess how
galactic properties influence inferred LyC escape. Despite significant variations in method predictions, there is broad consistency in the resulting weak and strong LyC leaker classifications, with approximately half exhibiting predicted escape fractions $>$1%. We find evidence for two different pathways of LyC escape in nearby
star-forming
galaxies: (1) an early escape model driven by very young
stellar populations, and (2) a delayed escape model that is consistent with
supernova-driven
outflows and time-dependent ISM clearing. The early escape model is favored among
galaxies with a single, intense burst of recent
star formation. In contrast, the delayed escape model is common among
galaxies with more extended starburst histories. To interpret ionizing
photon escape during the EoR, it will be necessary to recognize and understand this diversity in LyC escape mechanisms.
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All authors Kaelee S. Parker, Danielle A. Berg, John Chisholm, Simon Gazagnes, Sophia R. Flury, Cody Carr, Mason Huberty, Anne E. Jaskot, Matthew J. Hayes, Alberto Saldana-Lopez, Svea Hernandez, Themiya Nanayakkara, Bethan L. James, Karla Z. Arellano-Córdova, Allison Strom, Peter Senchyna, Matilde Mingozzi, Timothy Heckman, Xinfeng Xu, Alaina Henry, Ricardo O. Amorín, Valentin Mauerhofer, Crystal L. Martin, Dawn K. Erb, Evan D. Skillman, Kate H. R. Rubin, John Trevino, Claus Leitherer
Astrophysics of Galaxies
Mean Mass Density near the Sun from the Divergence Theorem and Pulsar Accelerations
Thomas Donlon II, Lawrence M. Widrow and Sukanya Chakrabarti
We introduce a new, non-parametric method for estimating the mass enclosed within a sphere of arbitrary radius centered on the Sun. The method is based on the divergence
theorem as applied to measurements of the line-of-sight accelerations of millisecond
pulsars. We describe a procedure for inferring the mean mass density within a sphere of a given radius centered on the Sun and find results that are consistent with previous analyses. When combined with a model for the distribution of
baryons, this provides the mean mass density of dark matter as a function of distance from the Sun, rather than a single value as is typically reported by kinematic studies. However, with the present
pulsar data, the method cannot unambiguously measure a signal from the local distribution of dark matter at this time; such a measurement is expected to soon become possible as the amount of
pulsar acceleration data grows and its precision improves. We derive an extension of the well-known shell
theorem to a spherical-harmonics expansion of the density and potential, and use the result to obtain estimates for density asymmetries with respect to the
Galactic midplane from the observed acceleration data. The predicted asymmetries do not follow the observed distribution of MW disk
stars or gas; this can potentially be explained by a non-uniform distribution of dark matter in the
Solar neighborhood.
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Cosmology and Nongalactic Astrophysics
DESI-Like Hubble Expansion From Staged Symmetry Breaking: Constraints on Renormalizable Models
Zachary J. Hoelscher, Thomas W. Kephart, Robert J. Scherrer et al. (+1 more)
The Dark Energy Spectroscopic Instrument (DESI) second data release shows a moderate preference for dark energy with a time-varying equation of state parameter, suggesting that the standard $\Lambda$CDM model may need to be revised. In particular, DESI favors dark energy whose equation of state parameter can drop below $-1$, violating the null energy condition. Chen and Loeb have recently suggested that this violation may be avoided if a subcomponent of the dark matter possesses a time-dependent equation of state. In this work, we explore the space of possible models, in an effort to find a natural, renormalizable realization. We find that once one requires the model to be renormalizable, a construction that generates the desired expansion history is fairly broadly obstructed. While we are unable to produce a fully natural, renormalizable realization of their ideas, this work is valuable for constraining directions one might pursue for viable theoretical explanations of the DESI results. Our framework is also interesting for incorporating features that may be of interest for model building elsewhere, as our decay cascades enable decays that switch on at particular
redshifts while also naturally incorporating a self-interacting dark matter candidate with a velocity-dependent cross section as a consequence of gauge invariance. The second feature is relevant for addressing tensions between $\Lambda$CDM and observations of small-scale structure, particularly the diversity of
galactic rotation curves.
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All authors Zachary J. Hoelscher, Thomas W. Kephart, Robert J. Scherrer, Kelly Holley-Bockelmann
Earth and Planetary Astrophysics
Methane on the temperate exo-Saturn TOI-199b
Aaron Bello-Arufe, Renyu Hu, Mantas Zilinskas et al. (+10 more)
Temperate ($T_{\rm eq}<400$ K) gas
giants represent an unexplored frontier in
exoplanet atmospheric spectroscopy. Orbiting a G-type
star every $\sim100$ days, the Saturn-mass
exoplanet TOI-199 b ($T_{\rm eq}=350$ K) is one of the most favorable low-temperature gas
giants for atmospheric study. Here, we present its transmission spectrum from a single transit observed with JWST's NIRSpec G395M mode. Despite lower-than-nominal precision due to a pointing misalignment, the spectrum reveals the presence of CH$_4$ (Bayes factor of $\sim$700 in a cloudy atmosphere), corresponding to a
metallicity of $\rm{C/H}=13^{+78}_{-12}\times$
solar, although the absence of detectable CO and CO$_2$ at the current precision disfavors
metallicities $\gtrsim50\times$
solar. We also tested several haze prescriptions (Titan-like tholin, soot, and water-rich tholin), but the preference for these models is weak (Bayes factors of $\sim 2$ relative to the clear case). The spectrum also shows an increase in transit depth near 3 $\mu$m, which our self-consistent models attribute to either NH$_3$ or, less likely, HCN. Follow-up observations could distinguish between these species, helping determine the
planet's vertical mixing regime. The TOI-199 system exhibits strong transit timing variations (TTVs) due to an outer non-transiting
giant planet. For
planet c, our TTV analysis reduces its mass uncertainty by 50% and prefers a slightly longer orbital period (but still within the conservative habitable zone) and higher eccentricity relative to previous studies. TOI-199 b serves as the first data point for studying clouds and hazes in temperate gas
giants, with the detection of spectral features in its transmission spectrum indicating that temperate gas
giants are promising targets for detailed atmospheric characterization.
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All authors Aaron Bello-Arufe, Renyu Hu, Mantas Zilinskas, Jeehyun Yang, Armen Tokadjian, Luis Welbanks, Guangwei Fu, Michael Greklek-McKeon, Mario Damiano, Jonathan Gomez Barrientos, Heather A. Knutson, David K. Sing, Xi Zhang
Cosmology and Nongalactic Astrophysics
Observational constraints on the product of dark energy chemical potential and number density in out-of-equilibrium models
J. M. Costa Netto, Javier E. Gonzalez and H. H. B. Silva
In this work, we impose observational limits on the product of dark energy chemical potential, $\mu$, and number density, $n$, at the present time in out-of-
equilibrium models, considering that particles can be created or destroyed in the fluid at a rate $\Gamma=3\alpha H(a)$, where $\alpha$ is a constant and $H(a)\equiv\dot{a}/a$ is the Hubble parameter. We combine the bounds derived from the positivity of
entropy and the second law of thermodynamics with observational constraints on the Chevallier-Polarski-Linder (CPL) and Barboza-Alcaniz (BA) parameterizations of the equation of state (EoS) of the component. We use Type Ia
supernovae (SN Ia) data from Pantheon+;
baryon acoustic oscillation (BAO) data from DESI DR2; and
cosmic microwave background (CMB) measurements from Planck. For $\alpha>0$ (particle creation), the thermodynamic restrictions yield only upper limits for the $\mu_{0}n_{0}$ product, while in the case of $\alpha<0$ (particle destruction) they establish both upper and lower limits, allowing for a range of values to be obtained. In both scenarios, however, we find that the chemical potential of dark energy must be negative, $\mu<0$, which indicates a preference for the phantom regime. In particular, when $\alpha<0$, it is noted that the thermodynamic bounds are simultaneously compatible only for very small absolute values of $\alpha$, with $\alpha=-0.0002$ being the limiting case and resulting in $\mu_{0}n_{0}(\alpha=-0.0002)=-2.2_{-0.7}^{+1.0}\,\,GeV/m^{3}$.
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Instrumentation and Methods for Astrophysics
The SPHEREx Image and Spectrophotometry Processing Pipeline
Rachel Akeson, Gregory P. Dubois-Felsmann, Brendan P. Crill et al. (+41 more)
In this paper, we describe the SPHEREx image and spectrophotometry data processing pipeline, an infrastructure and software system designed to produce calibrated spectral images and photometric measurements for NASA's SPHEREx mission. SPHEREx is carrying out a series of four all-sky spectrophotometric surveys at 6.15 arcsecond resolution in 102 spectral channels spanning 0.75 to 5 microns. The pipeline which will deliver the flux- and wavelength-calibrated data products deriving from these surveys has been developed and is operated by the SPHEREx Science Data Center at Caltech/IPAC in collaboration with the SPHEREx Science Team. Here we describe the framework and modules used in the pipeline, along with the data products, which are available at the NASA/IPAC Infrared Science Archive.
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All authors Rachel Akeson, Gregory P. Dubois-Felsmann, Brendan P. Crill, Andreas L. Faisst, Tamim Fatahi, Candice M. Fazar, Tatiana Goldina, Daniel C. Masters, Christina Nelson, Roberta Paladini, Harry I. Teplitz, Gabriela Torrini, Phani Velicheti, Matthew L. N. Ashby, Dan Avner, Yoonsoo P. Bach, James J. Bock, Sean Bruton, Sean A. Bryan, Tzu-Ching Chang, Shuang-Shuang Chen, Asantha Cooray, Ari J. Cukierman, O. Dore, C. Darren Dowell, Spencer Everett, Richard M. Feder, Zhaoyu Huai, Howard Hui, Woong-Seob Jeong, Young-Soo Jo, Phil M. Korngut, Yuna G. Kwon, Bomee Lee, Gary J. Melnick, Giulia Murgia, Chi H. Nguyen, Milad Pourrahmani, Zafar Rustamkulov, Volker Tolls, Teresa Symons, Pao-Yu Wang, Yujin Yang, Michael Zemcov
Earth and Planetary Astrophysics
Numerical Determination of the Gravitational Cross Sections of an Accreting Binary
Zachary Murray
A significant amount of work has been devoted to the study of small binary
solar system objects. The majority of these binaries, especially among the near-earth or main belt asteroids have small radius ratios, implying a large difference in size between the primary and its companion. Farther from the sun, the binary fraction increases, with the Kuiper Belt having many known binaries with radius ratios of order unity. In this paper, we consider the runaway growth of a binary system in an accretionary stream of small particles. We perform brute-force integrations, each with 10 million test particles and numerically compute the gravitational cross sections for each member of the binary as a function of the system's separation and mass ratio. We show that the behavior of the cross section is complex, and it can be either diminished or enhanced depending on the orbital configuration. In the regime where gravitational focusing dominates the
accretion process, we show that binaries grow towards smaller mass ratios than would be expected given single-body cross sections. Finally, we provide a grid of these cross sections for use in the future study of such systems.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Streamlined Supergravity
Renata Kallosh and Andrei Linde
The textbook N=1 supergravity has an F-term potential depending on a superpotential $W(z_i)$ and a Kahler potential $K(z^i, \bar z^{\bar i})$, with the scalar potential $V(z^i, \bar z^{\bar i})=e^K (|DW|^2 - 3 |W|^2)$. In this approach, it is not always easy to find the potential $V(z^i, \bar z^{\bar i})$ with the required properties. We show that in supergravity with a nilpotent superfield and with any Kahler potential $K(z^i, \bar z^{\bar i} )$ one can obtain any desired potential $V(z^i, \bar z^{\bar i})$ by a proper choice of the Kahler metric of the nilpotent superfield. This construction is particularly suitable for cosmological and particle physics applications, which may require maximal freedom in the choice of kinetic terms and scalar potentials.
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Astrophysics of Galaxies
Revised optical classification of a sample of gamma-ray emitting AGN with GTC and VLT
B. Dalla Barba, L. Foschini, M. Berton et al. (+10 more)
We report the results of the optical follow-up of a sample of $\gamma$-ray-emitting active
galactic nuclei (AGN). New high-quality optical spectra were obtained using Gran Telescopio Canarias with Optical System for Imaging and low- Intermediate-Resolution Integrated Spectroscopy and the European Southern Observatory Very Large
Telescope Unit
Telescope 1 with the FOcal Reducer and low dispersion Spectrograph 2. From the analysis of these spectra, we confirmed the previous classification as narrow-line Seyfert 1 (NLS1) for four objects and discovered two new NLS1s, bringing the total number of optically confirmed $\gamma$-NLS1s to 26. We also identified two ambiguous cases between NLS1 and intermediate Seyfert (IS), three IS, one broad-line Seyfert 1, one Seyfert 2. Based on the new spectra, we calculated black hole masses ranging from $10^{6.25}$ to $10^{9.32}$ $M_\odot$, and Eddington ratios spanning 0.05 to 2.07. This reclassification reinforces the scenario in which AGN with relatively small black hole masses are capable of launching powerful relativistic jets, contributing to our broader understanding of $\gamma$-ray-emitting AGN.
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All authors B. Dalla Barba, L. Foschini, M. Berton, E. Järvelä, P. Marziani, S. Ciroi, E. Dalla Bontà, L. Crepaldi, A. Vietri, S. Antón, M.J.M. Marchã, P. Condò, C. Mazzucchelli
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Structure Formation with Dark Magnetohydrodynamics
Pierce Giffin, Andrew Liu, Jeremias Boucsein et al. (+4 more)
Long-range interactions in the dark sector can give rise to collective
plasma phenomena that are capable of modifying the
evolution of dark matter
halos. We present the first study of gravitational collapse in a secluded dark $U(1)_D$ model using a magnetohydrodynamic description of the dark matter. We show that dark
magnetic fields generate an anisotropic pressure that alters the Jeans scale and suppresses small-scale power in a direction-dependent manner. For a range of
primordial magnetic spectral indices, this effect produces distinctive modifications to the linear matter power spectrum. We find that current observations cannot yet constrain viable dark
magnetic fields, as CMB tensor modes mostly provide more stringent constraints. Nevertheless, forthcoming high-resolution probes of the matter power spectrum (CMB-HD
lensing, HERA, and EDGES) will be able to test these predictions and are sensitive to dark charge-to-mass ratios in the range $10^{-20}\,\text{GeV}^{-1}\lesssim q_\chi/m_\chi\lesssim 10^{-14}\,\text{GeV}^{-1}$.
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All authors Pierce Giffin, Andrew Liu, Jeremias Boucsein, Akaxia Cruz, Anirudh Prabhu, Stefano Profumo, M. Grant Roberts
Astrophysics of Galaxies
Unveiling Chemical Enrichment in the Abell 2029 Core with XRISM, XMM-Newton, and Chandra
Arnab Sarkar, Eric D. Miller, Brian McNamara et al. (+6 more)
We present new measurements of the chemical abundance pattern in the core of the nearby
galaxy cluster Abell~2029, based on XRISM observations with Resolve (37 ks) and Xtend (500 ks), combined with archival data from XMM-Newton (EPIC, RGS) and Chandra. Fe abundances derived from Resolve, Xtend, and EPIC are broadly consistent, while RGS gives systematically lower values. Because the XRISM gate valve remained closed during these observations, Resolve spectral fitting is restricted to the 2–10 keV band, providing reliable constraints only for elements with strong lines in this band (S, Ar, Ca, Fe, Ni). Abundances of the $\alpha$-elements are therefore derived using complementary observations from Xtend, EPIC, RGS, and Chandra. We construct an average X/Fe pattern in the cluster core by using Resolve exclusively for S/Fe, Ar/Fe, Ca/Fe, and Ni/Fe, and RGS + Xtend for O/Fe. The Ne/Fe ratio is averaged from Xtend, EPIC, RGS, and Chandra measurements; Mg/Fe from EPIC and Chandra measurements; and Si/Fe from Xtend, EPIC, and Chandra. Comparison with the
supernovae yield models indicates that the observed abundance pattern in A2029 core is best reproduced by a combination of core-collapsed yields from low-
metallicity progenitors ($Z_{\rm init}=0.001$) and a sub-Chandrasekhar-mass, double-degenerate Type Ia model. Additionally, we find an excess in Ca abundance in the core of A2029 that cannot be reproduced by the standard
supernovae yield models.
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All authors Arnab Sarkar, Eric D. Miller, Brian McNamara, Ming Sun, Richard Mushotzky, Stefano Ettori, Lorenzo Lovisari, Irina Zhuravleva, Naomi Ota
Astrophysics of Galaxies
The abundance and properties of the lowest luminosity dwarf galaxies around the Milky Way: Insights from Semi-Analytic Models
Niusha Ahvazi, Andrew B. Pace, Christopher T. Garling et al. (+11 more)
We investigate the formation and observable properties of faint satellite
galaxies (M$_\rm V > -3$) in Milky Way-like
halos using the semi-analytic
galaxy formation model Galacticus. The ability of the smallest dark matter
halos to form
stars depends sensitively on the balance between gas cooling and reionization heating. To quantify how this balance shapes the abundance and properties of the faintest
galaxies, we compare two model variants: a fiducial model that includes molecular hydrogen (H$_2$) cooling and UV background radiation, and a No-H$_2$ model with atomic cooling only. Both models reproduce the structural properties of brighter Milky Way satellites, but they diverge at the lowest luminosities in the hyper-faint regime. The fiducial model predicts a substantially larger population of such systems that are on average hosted in
halos with lower peak masses and quenched earlier. Many of these predicted systems lie below current observational thresholds but are within reach of next-generation deep imaging surveys. The predicted size-luminosity distributions of both models overlap with the region occupied by recently discovered "ambiguous" systems, whose classification as
galaxies or
star clusters remains uncertain. Specifically, we find that hyper-faint satellites have line-of-sight velocity dispersions of $\sigma_{\rm los} \sim 1-3$ km/s in the fiducial model, nearly an order of magnitude higher than expected for purely self-gravitating
stellar systems of the same
stellar mass. This distinction underscores the diagnostic power of precise kinematic measurements for determining whether ambiguous objects are dark matter dominated
dwarf galaxies or
star clusters, and highlights the importance of upcoming spectroscopic campaigns in resolving the nature of the faintest satellites.
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All authors Niusha Ahvazi, Andrew B. Pace, Christopher T. Garling, Xiaowei Ou, Nitya Kallivayalil, Paul Torrey, Andrew Benson, Aklant Bhowmick, Núria Torres-Albà, Alex M. Garcia, Alejandro Saravia, Jonathan Kho, Jack T. Warfield, Kaia R. Atzberger
Cosmology and Nongalactic Astrophysics
The Noisy Universe
Gabriela Barenboim, Aurora Ireland and Albert Stebbins
We present observational constraints on large-scale white noise (LSWN) in the
cosmic density field, a phenomenon predicted to arise from non-linear mode coupling during cosmological
evolution. Building on the theoretical framework of Paper I, where we demonstrated that non-linearities inevitably redistribute power from small to large scales through mode mixing, we confront these predictions with current cosmological data. We modify the CLASS Boltzmann code to incorporate a white noise component $k_\mathrm{BH}/k$ in the
primordial power spectrum and perform parameter estimation using current cosmological data. The non-detection of excess power on the largest observable scales places stringent upper bounds: $k_\mathrm{BH} \leq 1.80 \times 10^{-13}~\mathrm{Mpc}^{-1}$ at 99% confidence. These constraints imply the
primordial power spectrum must deviate from perfect scale invariance on small scales, either through a cutoff at $k_{\mathrm{cut}} \lesssim 3~\mathrm{pc}^{-1}$ or through running of the spectral index with $\alpha_s \lesssim -0.015$. Our results demonstrate that LSWN provides a powerful probe of the
primordial spectrum at scales orders of magnitude smaller than directly observable, offering unique constraints on early-universe physics.
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Astrophysics of Galaxies
Universal depletion of metal-poor globular clusters in inner galaxy regions: Fossil record of black hole retention
Ali Rostami-Shirazi, Narges Rostami, Hosein Haghi et al. (+1 more)
We analyzed the spatial distribution of globular cluster (GC) systems across 37 host
galaxies in a two dimensional parameter space defined by projected galactocentric distance Rg and
metallicity Fe/H. We identified a universal triangular depleted region characterized by a lack of metal poor GCs in the inner parts of host
galaxies. The morphology of this depleted region correlates with the luminous mass of the host
galaxies; more massive
galaxies consistently exhibit more extended depleted regions. We attribute this phenomenon to the combined influence of large scale
galactic assembly and internal GC dynamics, particularly the initial retention of black holes within GCs. Metal poor GCs contain a more massive and compact black hole subsystem, which drives more energetic few body encounters and injects greater kinetic energy into the
stellar population. This extra energy, combined with strong
tidal forces in central
galactic regions, accelerates the dissolution of low
metallicity GCs, producing the triangular depleted pattern in the Rg - Fe/H space. Stronger
tidal fields in more massive
galaxies confine surviving metal poor GCs to larger radii, broadening the depleted region. The morphology of this region may serve as a potential distance indicator for host
galaxies. Our results also suggest that scenarios with substantial black hole natal kicks are unlikely, as too few retained black holes would erase the
metallicity dependent cluster dissolution required to form the observed depletion region.
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All authors Ali Rostami-Shirazi, Narges Rostami, Hosein Haghi, Akram Hasani Zonoozi
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Scattering perspective on gravitational lensing
Mariana Carrillo Gonzalez, Valerio De Luca, Alice Garoffolo et al. (+2 more)
Gravitational waves propagating across gravitational potentials undergo
lensing effects that, in the wave-optics regime, manifest as frequency-dependent amplitude and phase modulations. In this work, we revisit the diffraction integral formalism of gravitational
lensing and demonstrate that it admits a natural and transparent interpretation within the framework of scattering theory. We establish a direct correspondence between the
lensing amplification factor and the scattering amplitude of waves propagating in curved spacetime, clarifying how familiar
lensing limits map onto distinct scattering regimes. In particular, we show that the diffraction integral matches exactly the eikonal limit of the scattering amplitude at lowest post-Minkowskian order, after a change in coordinates and the inclusion of finite-distance effects. We further extend the standard formalism by including subleading corrections to the post-Minkowskian and eikonal approximations. Our results provide a unified theoretical framework for the interpretation of lensed gravitational-wave signals and open the way to more accurate waveform modeling for future lensed observations.
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All authors Mariana Carrillo Gonzalez, Valerio De Luca, Alice Garoffolo, Julio Parra-Martinez, Mark Trodden
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Teukolsky by Design: A Hybrid Spectral-PINN solver for Kerr Quasinormal Modes
Alexandre M. Pombo and Lorenzo Pizzuti
We introduce SpectralPINN, a hybrid pseudo-spectral/physics-informed neural network (PINN) solver for Kerr quasinormal modes that targets the Teukolsky equation in both the separated (radial/angular) and joint two-dimensional formulations. The solver replaces standard neural activation functions with Chebyshev
polynomials of the first kind and supports both soft – via loss penalties – and hard – enforced by analytic masks – implementations of Leaver's normalization. Benchmarking against Leaver's continued-fraction method shows cumulative (real+imaginary part) relative frequency errors of $\sim 0.001\%$ for the separated formulation with hard normalization, $\sim 0.1\%$ for both the soft separated and soft joint formulations, and $\sim 0.01\%$ for the hard joint case. Exploiting our ability to solve the joint equation, we add a small quadrupolar perturbation to the Teukolsky operator, effectively rendering the problem non-separable. The resulting perturbed quasinormal modes are compared against the expected precision of the Einstein
Telescope, allowing us to constrain the magnitude of the perturbation. These proof-of-concept results demonstrate that hybrid spectral-PINN solvers can provide a flexible pathway to quasinormal spectra in settings where separability, asymptotics, or field content become more intricate and high accuracy is required.
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Astrophysics of Galaxies
The MeerKAT Fornax Survey VI. The collapse of the galaxy HI Mass Function in Fornax
D. Kleiner, P. Serra, A. Loni et al. (+6 more)
We present the deepest HI mass Function (HIMF) ever measured, outside the Local Group. The observations are part of the MeerKAT Fornax Survey and cover a 4 x 4 deg^2 field, corresponding to ~ Rvir. The 3$\sigma$ detection limit is log(MHI/Msun) = 5.7 for a 50 km/s-wide point source. We detect HI in 35
galaxies and 44 clouds with no optical counterparts. Using deep optical images from the Fornax Deep Survey, we show that the clouds are a distinct population, separated by a four magnitude gap from the faintest HI-detected
galaxies. The majority (33 out of 44) of the clouds are associated with the two
galaxies with the most HI in the cluster – NGC 1365 and NGC 1427A, although the clouds contribute a negligible amount to the total MHI budget. By performing a SNR analysis and computing the Rauzy statistic on the HI detections, we demonstrate that our catalogue is complete down log(MHI/Msun) = 6, and we are therefore able to probe the HIMF down to this level. We find an abrupt drop of the number density of HI-detected
galaxies at log(MHI/Msun) = 7, signifying a clear absence of
galaxies between 6 < log(MHI/Msun) < 7. We use the modified maximum likelihood method to fit a Schechter function down to log(MHI/Msun) > 7, the range where the HIMF follows a power-law. The measured low-mass slope is $\alpha$ = -1.31 $\pm$ 0.13, with a characteristic knee mass of log(M*/Msun) = 10.52 $\pm$ 1.89. The low-mass slope matches the slope in the field, while the knee is defined by a single
galaxy and is unconstrained. Below log(MHI/Msun) = 7, there is a sharp departure from a Schechter function, and we report the first robust measurement of the collapse of a HIMF. For the HIMF below log(MHI/Msun) = 7 to follow a power-law, tens of
galaxies are needed – a factor ~ six higher than what is observed. The collapse of the Fornax HIMF is likely due to the rapid removal of HI from low-mass
galaxies.
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All authors D. Kleiner, P. Serra, A. Loni, S. H. A. Rajohnson, F. M. Maccagni, W. J. G. de Blok, P. Kamphuis, R. C. Kraan-Korteweg, M. A. W. Verheijen
High Energy Astrophysical Phenomena
How Bright in Gravitational Waves are Millisecond Pulsars for the Galactic Center GeV Gamma-Ray Excess? A Systematic Study and Implications for Dark Matter
Ming-Yu Lei, Bei Zhou and Xiaoyuan Huang
The existence of dark matter (DM) is supported by various macroscopic observations, but its microscopic nature remains elusive. The
Galactic Center GeV gamma-ray excess (GCE) has been a leading candidate signal for particle DM annihilation. However, an unresolved population of millisecond
pulsars (MSPs) in the bulge provides the alternative explanation for the excess. Identifying these MSPs in electromagnetic bands is difficult due to source confusion, pulse broadening, and extinction. Gravitational waves (GWs) provide a complementary probe: a steadily rotating, non-axisymmetric MSP emits a nearly monochromatic GW signal in the sensitive band of ground-based detectors, with amplitude set by its ellipticity. In this work, we systematically investigate the GW emission from the MSP population proposed to explain the GCE and its detectability with current and future detectors. We consider three major scenarios for the origin of ellipticity and model the population properties of these MSPs. We also consider both isolated MSPs and MSPs in binary systems, as well as Doppler effects in the detection. We find that while the signal is below the reach of current interferometers, next-generation detectors such as the Einstein
Telescope (ET) and
Cosmic Explorer (CE) may detect a fraction of those MSPs, offering a novel test of the MSP interpretation of the GCE. Future directed searches toward the
Galactic Center with continued improvements in sensitivities will either uncover this long-sought MSP population or place stringent limits on their ellipticities and abundance, with important implications for both the astrophysical and DM interpretations of the GCE.
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Astrophysics of Galaxies
A first look at a complete view of spatially resolved star formation at 1<z<1.8 with JWST NGDEEP+FRESCO slitless spectroscopy
Jasleen Matharu, Lu Shen, Irene Shivaei et al. (+15 more)
[abridged] The previously inaccessible
star formation tracer Pa$\alpha$ can now be spatially resolved by JWST NIRCam slitless spectroscopy in distant
galaxies up to
cosmic noon. In the first study of its kind, we combine JWST NGDEEP NIRISS and FRESCO NIRCam slitless spectroscopy to provide the first direct comparison of spatially resolved
dust-obscured (traced by Pa$\alpha$) versus unobscured (traced by H$\alpha$)
star formation across the main sequence. We stack Pa$\alpha$ and H$\alpha$ emission-line maps, along with
stellar continuum images at both wavelengths of 31
galaxies at 1<z<1.8 in three bins of
stellar mass. Surface brightness profiles are measured and equivalent width (EW) profiles computed. Increasing Pa$\alpha$ and H$\alpha$ EW profiles with galactocentric radius across all
stellar masses probed provide direct evidence for the inside-out growth of
galaxies both via
dust-obscured and unobscured
star formation for the first time. For
galaxies on the main sequence, a weakly positive ($0.1\pm0.1$) Pa$\alpha$/H$\alpha$ line profile as a function of radius is found at $8.8\leqslant\mathrm{log}(M_{*}/\mathrm{M}_{\odot})<9.9$ with a negative ($-0.4\pm0.1$) Pa$\alpha$/H$\alpha$ line profile found at $9.9\leqslant\mathrm{log}(M_{*}/\mathrm{M}_{\odot})<11.0$. Low mass
galaxies ($7.7\leqslant\mathrm{log}(M_{*}/\mathrm{M}_{\odot})<8.8$) with high sSFRs are found to have a negative ($-0.5\pm0.1$) Pa$\alpha$/H$\alpha$ line profile gradient. Our results demonstrate that while inside-out growth via
star formation is ubiquitous across the main sequence just after
cosmic noon, centrally concentrated
dust attenuation is not. Along with other recent work in the literature, our findings motivate future studies of resolved SFR profiles in large samples of individual
cosmic noon
galaxies across the main sequence, to understand the intrinsic scatter in spatially resolved
star formation.
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All authors Jasleen Matharu, Lu Shen, Irene Shivaei, Pascal A. Oesch, Casey Papovich, Gabriel Brammer, Naveen A. Reddy, Yingjie Cheng, Pieter van Dokkum, Steven L. Finkelstein, Nimish P. Hathi, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Jorryt Matthee, Nor Pirzkal, Stephen M. Wilkins, Michael A. Wozniak, Mengyuan Xiao
Astrophysics of Galaxies
Electron densities from [S II] lines significantly overestimate the impact of ionised AGN outflows
Luke R. Holden, Daniel J. B. Smith, Marina I. Arnaudova et al. (+6 more)
To explain the properties of the local
galaxy population, theoretical models require active
galactic nuclei (AGN) to inject energy into host
galaxies, thereby expelling
outflows of gas that would otherwise form
stars. Observational tests of this scenario rely on determining
outflow masses, which requires measuring the electron density ($n_e$) of ionised gas. However, recent studies have argued that the most commonly used diagnostic may underestimate electron densities (and hence overestimate
outflow masses) by several orders of magnitude, casting doubt as to whether ionised AGN-driven
outflows can provide the impact needed to reconcile observations with theory. Here, we investigate this by applying two different electron-density diagnostics to Sloan Digital Sky Survey (SDSS) spectroscopy of the
Quasar Feedback (QSOFEED) sample of 48 nearby type-2
quasars. Accounting for uncertainties, we find that
outflow masses implied by the transauroral-line electron-density diagnostic are significantly lower than those produced by the commonly-used `strong-line' [S II](6717/6731) method, indicating a different origin of these emission lines and suggesting that these doubts are justified. Nevertheless, we show that it is possible to modify the [S II](6717/6731) electron-density diagnostic for our sample by applying a correction of $\mathrm{log}_{10}(n_{e\mathrm{,\, outflow}}\mathrm{ [cm}^{-3}\mathrm{]}) = \mathrm{log}_{10}(n_{e\mathrm{,[S\,II]}}\mathrm{ [cm}^{-3}\mathrm{]}) + 0.75(\pm0.07)$ to account for this, which results in values that are statistically consistent with those produced using the transauroral-line method. The techniques that we present here will be crucial for
outflow studies in the upcoming era of large spectroscopic surveys, which will also be able to verify our results and broaden this method to larger samples of AGN of different types.
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All authors Luke R. Holden, Daniel J. B. Smith, Marina I. Arnaudova, Clive. N. Tadhunter, Cristina Ramos Almeida, Shravya Shenoy, Pedro H. Cezar, Soumyadeep Das, Akshara Binu
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
How light can ALP dark matter be?
Kierthika Chathirathas and Thomas Schwetz
We assume
axion-like particles (ALPs) to provide the full dark matter abundance and derive various lower bounds on the ALP mass. We contrast the post- and pre-inflationary
symmetry breaking cases and present allowed regions in the plane of ALP mass and energy scale of inflation. For the post-inflationary case, we revisit bounds from isocurvature perturbations taking into account that, as suggested by simulations,
axion radiation by
cosmic strings during the scaling regime provides the dominant production mechanism of dark matter, obtaining significantly weaker limits than previously. Combining isocurvature, with constraints from black hole superradiance and free streaming, we find that the bound $m_a \gtrsim 10^{-17}$ eV applies for most cases considered here. It can be potentially relaxed to $\sim 6\times 10^{-19}$ eV only in the post-inflationary case with a strongly temperature-dependent
axion mass, subject to uncertainties on the
axion emission spectrum. Significantly stronger bounds are obtained in the post-inflationary scenario from the non-observation of CMB tensor modes, which can be as strong as $m_a > 5\times 10^{-7}$ eV for small reheating efficiencies, $\epsilon \lesssim 5\times 10^{-4}$.
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Astrophysics of Galaxies
Do z>6 quasars reside in protoclusters?
Fabio Fontanot, Roberto Decarli, Gabriella De Lucia et al. (+3 more)
We discuss the properties of a sample of z>6 bright (bolometric luminosity L$_{\rm bolo}$>10$^{46.25}$ erg/s)
Quasars drawn from a realisation of the
GAlaxy Evolution and Assembly (GAEA) model coupled with the Planck Millennium Simulation. We focus on the properties and environment of host
galaxies on a physical scale of 10 cMpc, and their
evolution down to z=0, with the aim of assessing how well the bright high
redshift QSOs population traces the progenitors of the most massive
haloes in the local Universe. GAEA predicts that z>6 bright QSOs live in a variety of environments, and that secular processes like disc instability are responsible for triggering roughly the same number of QSOs as
galaxy mergers. We consider mock fields built around these high-z QSOs, and we show that roughly half of them include other active
galaxies (with L$_{\rm bolo}$>10$^{44}$ erg/s). The predicted large field-to-field variance in the number of companions is qualitatively consistent with recent results from JWST observations. Descendants of host
galaxies at z=0 cover a wide range of physical properties and environments with only a small fraction of them belonging to massive
galaxy clusters (M$_{\rm DM}$>10$^{14.5}$ M$_\odot$). Viceversa, GAEA predicts that only a small fraction of Bright Central
Galaxies have a bright z>6 QSOs among their progenitors. Our results suggest that luminous high-z QSO loosely trace the progenitors of low-z
galaxy clusters, but that additional information about their environment (like the number of active
galaxy companions) are required to identify the most promising proto-cluster candidates.
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All authors Fabio Fontanot, Roberto Decarli, Gabriella De Lucia, Olga Cucciati, Lizhi Xie, Michaela Hirschmann
Instrumentation and Methods for Astrophysics
Decoding the Radio Sky: Bayesian Ensemble Learning and SVD-Based Feature Extraction for Automated Radio Galaxy Classification
Theophilus Ansah-Narh, Jordan Lontsi Tedongmo, Joseph Bremang Tandoh et al. (+2 more)
The classification of
radio galaxies is central to understanding
galaxy evolution, active
galactic nuclei dynamics, and the large-scale structure of the universe. However, traditional manual techniques are inadequate for processing the massive, heterogeneous
datasets generated by modern
radio surveys. In this study, we present a probabilistic machine learning framework that integrates Singular Value Decomposition (SVD) for feature extraction with
Bayesian ensemble learning to achieve robust, scalable
radio galaxy classification. The SVD approach effectively reduces dimensionality while preserving key morphological structures, enabling efficient representation of
galaxy features. To mitigate class imbalance and avoid the introduction of artefacts, we incorporate a Local Neighbourhood Encoding strategy tailored to the astrophysical distribution of
galaxy types. The resulting features are used to train and optimize several baseline classifiers: Logistic Regression, Support Vector Machines, LightGBM, and Multi-Layer Perceptrons within bagging, boosting, and stacking ensembles governed by a
Bayesian weighting scheme. Our results demonstrate that
Bayesian ensembles outperform their traditional counterparts across all metrics, with the
Bayesian stacking model achieving a classification accuracy of 99.0% and an F1-score of 0.99 across Compact, Bent, Fanaroff-Riley Type I (FR-I), and Type II (FR-II) sources. Interpretability is enhanced through SHAP analysis, which highlights the principal components most associated with morphological distinctions. Beyond improving classification performance, our framework facilitates uncertainty quantification, paving the way for more reliable integration into next-generation survey pipelines. This work contributes a reproducible and interpretable methodology for automated
galaxy classification in the era of data-intensive
radio astronomy.
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All authors Theophilus Ansah-Narh, Jordan Lontsi Tedongmo, Joseph Bremang Tandoh, Nia Imara, Ezekiel Nii Noye Nortey
Earth and Planetary Astrophysics
Efficiency of Hydrodynamic Atmospheric Escape in Hot Jupiters and Super Earths
Renata Frelikh and Ruth A. Murray-Clay
We develop a flexible one-dimensional code to model the escape of hydrogen and helium from a hot Jupiter as a result of photoionization from extreme-ultraviolet (EUV) radiation. We include
stellar spectrum heating and ionization, radiative cooling by Lyman-$\alpha$ and H$_3^+$, heat conduction,
tidal gravity, a H-He reaction network, and account for the secondary ionization of species by photoelectrons. For a fiducial hot Jupiter, we uncover a three-layer structure: an H$_3^+$-cooled layer of molecular hydrogen at the base, enveloped by a Lyman-$\alpha$-cooled layer of neutral hydrogen, which transitions into an ionized wind layer that is cooled by adiabatic expansion. The highest spectral energy
photons are deposited in the molecular layer, where, after accounting for energy loss via photoelectrons and ionization, H$_3^+$ is a substantial radiative coolant. We run a grid of models, varying the distance of our fiducial
planet from the
star. We find that heat conduction at the base starts to have an effect at distances $\gtrsim 0.2$ au, increasing the H$_3^+$ cooling relative to the EUV input flux. At increasing stellocentric distances, the
outflow becomes increasingly more neutral. The neutral hydrogen starts to decouple from the ionized
outflow, free-streaming out. In pure H-He mini-Neptune/super-Earth simulations, the
outflows are significantly cooler, allowing molecules to survive throughout the
outflow, pointing toward the likely importance of molecular cooling in determining whether these
planets can maintain massive atmospheres. The analysis in this paper provides a framework for understanding the impact of molecular radiative cooling on atmospheric
outflows.
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