Astrophysics of Galaxies
Dily Duan Yi Ong, Francesco D'Eugenio, Roberto Maiolino et al. (+13 more)
Observations have suggested that
galactic outflows contain substantial amounts of dense and clumpy molecular gas, creating favourable conditions for igniting
star formation. Indeed, theoretical models and hydrodynamical simulations have suggested that
stars could form within
galactic outflows, representing a new mode of
star-formation that differs significantly from the typical
star formation in
star forming discs. In this paper, we examine 12 local
galaxies with powerful Active
Galactic Nuclei and high
star-formation rate using spectroscopic data from the X-shooter spectrograph at the Very Large
Telescope. We investigate the excitation mechanism and physical properties of these
outflows via spatially resolved diagnostic diagrams (along with tests to rule out contribution by shocks and external photoionisation). Out of the seven
galaxies with clearly detected
outflows, we find robust evidence for
star formation within the
outflow of one
galaxy (IRAS 20551-4250), with two additional
galaxies showing tentative signs (IRAS 13120-5453 and F13229-2934). Therefore, our findings support previous results that
star formation inside
outflows can be a relatively common phenomenon among these active
galaxies and may have played an important role in the formation and
evolution of the spheroidal component of
galaxies.
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All authors Dily Duan Yi Ong, Francesco D'Eugenio, Roberto Maiolino, Santiago Arribas, Francesco Belfiore, Enrica Bellocchi, Stefano Carniani, Sara Cazzoli, Giovanni Cresci, Andrew Fabian, Wako Ishibashi, Filippo Mannucci, Alessandro Marconi, Helen Russell, Eckhard Sturm, Giacomo Venturi
High Energy Astrophysical Phenomena
Detection prospects for heavy WIMP dark matter near supermassive black holes, particularly in M31
Andrei E. Egorov
This work analyzes the detection prospects for weakly interacting massive particles (WIMPs) in dark matter (DM) density spikes around nearby supermassive black holes (SMBHs) by observations in very high energy gamma-ray band. Such spikes are unique targets, which provide a possibility to discover the basic thermal s-wave annihilating WIMP with any mass up to the theoretical unitarity limit ~ 100 TeV. All relevant SMBHs were checked, and only MW* and M31* were identified as worthwhile objects. Cherenkov
Telescope Array (CTA) sensitivity to heavy WIMPs in M31* was estimated. It was obtained that CTA will be able to probe a major part of TeV-scale WIMP parameter space in case of optimistic spike density configuration in M31*. In certain scenarios, M31* may yield even stronger constraints than MW*. Relevant systematic uncertainties were explored.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Heterogeneous Cosmological Phase Transitions: Seeded by Domain Walls and Junctions
Yang Bai, Yifu Xu and Yiming Yang
Heterogeneous nucleation is central to many familiar first-order phase transitions such as the freezing of water and the solidification of metals, and it can also play a crucial role in cosmology. We examine nucleation seeded by preexisting domain walls and demonstrate its strong impact on the dynamics of cosmological phase transitions. The bubble solutions take the form of spherical caps, and the contact angle is fixed by the ratio of the domain-wall tension to the bubble-wall tension. A larger domain-wall tension, or equivalently a smaller contact angle, reduces the wall-seeded bubble volume and lowers the critical nucleation action. For theories with $\mathbb{Z}_{n\geq 3}$
symmetry, domain-wall junctions naturally appear and we find that they seed nucleation even more efficiently than the walls themselves. Using a two-scalar-field model as an illustration, we compute nucleation temperatures for both homogeneous and heterogeneous channels and show that junction-seeded nucleation occurs at a higher temperature and is the dominant mechanism that completes the first-order cosmological phase transition.
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Earth and Planetary Astrophysics
Shedding Light on Large Space-Based Telescopes: Modeling Stray Light due to Primary Mirror Damage from Micrometeoroid Impacts
Megan T. Gialluca, Jonathan W. Arenberg, Chris Stark et al. (+5 more)
A large space-based
telescope aimed at detecting and characterizing the atmospheres of Earth-like
planets orbiting Sun-like
stars will require unprecedented contrast and stability. However, damage to the primary mirror due to micrometeoroid impacts will provide a
stochastic, time-dependent source of stray light in the coronagraph's field of view that could significantly lengthen exposure times and reduce the expected science yield. To better quantify the impact of stray light and inform the Habitable Worlds Observatory mission design process, we present estimates of stray light in different micrometeoroid damage scenarios for a broad range of targets, and use that to find the expected decrease in science yield (i.e., the expected number of detected exoEarth candidates). We find that stray light due to micrometeoroid damage may significantly reduce yield, by 30% – 60% in some cases, but significant uncertainties remain due to the unknown maximum expected impactor energy, and the relationship between impact energy and expected crater size. Micrometeoroid damage therefore needs further exploration, as it has the potential to reduce scientific yield, and in turn drive the development of mitigation strategies, selection of
telescope designs, and selection of observing priorities in the future.
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All authors Megan T. Gialluca, Jonathan W. Arenberg, Chris Stark, Blake Shepherd, Victoria S. Meadows, Aki Roberge, Tyler D. Robinson, Robert Podgurski
Earth and Planetary Astrophysics
A Stellar Magnesium to Silicon ratio in the atmosphere of an exoplanet
Jorge A. Sanchez, Peter C. B. Smith, Krishna Kanumalla et al. (+17 more)
The elemental compositions of
exoplanets encode information about their formation environments and internal structures. While volatile ratios such as carbon-to-oxygen (C/O) are used to trace formation location, the rock-forming elements - magnesium (Mg), silicon (Si), and iron (Fe) - govern interior mineralogy and are commonly assumed to reflect the host
star's abundances. Yet this assumption remains largely untested. Ultra-hot Jupiters, gas-
giant exoplanets with dayside temperatures above 3000 K, provide rare access to refractory elements that remain gaseous. Here we present high-resolution thermal emission spectroscopy of the
exoplanet WASP-189b (Teq = 3354^{+27}_{-34} K) obtained with the Immersion Grating Infrared Spectrometer (IGRINS) on Gemini South. We detect neutral iron (Fe I), magnesium (Mg I), silicon (Si I), water (H_2O), carbon monoxide (CO), and hydroxyl (OH) at signal-to-noise ratios exceeding 4, and retrieve their elemental abundances. We show that the Mg/Si, Fe/Mg, and Si/Fe ratios are consistent with
stellar values, while the refractory-to-volatile ratio is enhanced by roughly a factor of ~2. These findings demonstrate that
giant-
planet atmospheres can preserve
stellar-like rock-forming ratios, providing an empirical validation of the
stellar-proxy assumption that underpins planetary composition and formation models across
exoplanet systems.
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All authors Jorge A. Sanchez, Peter C. B. Smith, Krishna Kanumalla, Luis Welbanks, Michael R. Line, Stefan Pelletier, Steven Desch, Patrick Young, Jennifer Patience, Jacob Bean, Matteo Brogi, Dan Jaffe, Gregory N. Mace, Megan Weiner Mansfield, Vatsal Panwar, Vivien Parmentier, Lorenzo Pino, Arjun Baliga Savel, Lennart van Sluijs, Joost P. Wardenier
Instrumentation and Methods for Astrophysics
A vision for ground-based astronomy beyond the 2030s: How to build ESO's next big telescope sustainably
Laurane Fréour, Mathilde Bouvier, Tony Mroczkowski et al. (+8 more)
Astronomy is the study of the Universe and all the objects that it comprises. Our
attention is therefore usually focused beyond Earth, home to the only form of life known today. However, how can we continue to explore the secrets of the Universe, if we stand by and watch our only home burn? We know that there is no
Planet B. It is therefore urgent that, as astronomers, we collectively work to protect the Earth, allowing future generations the opportunity to continue to uncover the secrets of the cosmos. As astronomical facilities account for the majority of our community's carbon footprint, we propose guidelines that we hold crucial for the European Southern Observatory (ESO) to consider in the context of the Expanding Horizons programme as it plans a next-generation, transformational facility.
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All authors Laurane Fréour, Mathilde Bouvier, Tony Mroczkowski, Callie Clontz, Fatemeh Zahra Majidi, Vasundhara Shaw, Olivier Absil, Anna Cabré, Olivier Lai, Dylan Magill, Jake D. Turner
Cosmology and Nongalactic Astrophysics
Updated and Projected Cosmic Microwave Background Bounds on WIMP Annihilation
Charlotte Myers, Dominic Agius, Daniele Gaggero et al. (+1 more)
We derive updated
Cosmic Microwave Background (CMB) constraints on annihilating dark matter, and present forecasts for upcoming CMB surveys. We show that the addition of recent temperature, polarization, and
lensing data from ground-based experiments yields only minor improvements ($\approx 10\%$) compared to Planck bounds, confirming that the sensitivity remains dominated by the large-scale E-mode polarization. Forecasts, using a LiteBIRD-like setup, indicate that pairing a low-noise, wide-sky satellite at $\ell < 200$ with high-resolution ground observations nearly saturates the
cosmic-variance limit, improving bounds by $\approx 60\%$, where our derived 95th percentile limit is $p_{\rm ann} < 1.27{\times}10^{-28}\,\mathrm{cm^{3}\,s^{-1}\,GeV^{-1}}$. We also consider the inclusion of B-mode polarization for a realistic future experiment.
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All authors Charlotte Myers, Dominic Agius, Daniele Gaggero, Angelo Ricciardone
High Energy Astrophysical Phenomena
The LISA Astrophysics "Disc-IMRI" Code Comparison Project: Intermediate-Mass-Ratio Binaries in AGN-Like Discs
Andrea Derdzinski, Alexander J. Dittmann, Alessia Franchini et al. (+16 more)
Upcoming space-based gravitational wave detectors such as LISA, the
Laser Interferometer Space
Antenna, will be sensitive to extreme- and intermediate-mass-ratio inspirals (EMRIs and IMRIs). These binaries are comprised of a supermassive black hole and a
stellar-mass object or intermediate-mass black hole. Their detection will probe the structure of
galactic nuclei and enable tests of general relativity. As these events will be observed over thousands of orbital cycles, they will be extremely sensitive to both the underlying spacetime and astrophysical environment, demanding exquisite theoretical models on both fronts to avoid biased or even erroneous results. In particular, many (E/)IMRIs are expected to occur within
accretion discs around supermassive black holes, and the nonlinearities present when modeling these systems require numerical simulations. In preparation for future modeling of LISA sources, we have conducted a comparison between eight different hydrodynamical codes and applied them to the problem of a q = 10^{-4} mass ratio binary interacting with an
accretion disc. Thicker discs appear more lenient, and all codes at sufficiently high resolutions are in good agreement with each other and analytical predictions. For thinner discs, beyond the reach of analytical models, we find substantial disagreement between 2D and 3D simulations and between different codes, including both the magnitude and sign of the torque. With time and energy efficiency in mind, codes that leverage moving meshes or grid-based Lagrangian remapping seem preferable, as do codes that can leverage graphical processing units and other energy-efficient hardware.
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All authors Andrea Derdzinski, Alexander J. Dittmann, Alessia Franchini, Alessandro Lupi, Noé Brucy, Pedro R. Capelo, Frédéric S. Masset, Raphaël Mignon-Risse, Michael Rizzo Smith, Edwin Santiago-Leandro, Martina Toscani, David A. Velasco-Romero, Robert Wissing, Mudit Garg, Lucio Mayer, Roberto Serafinelli, Lazaros Souvaitzis, Daniel J. D'Orazio, Jonathan Menu
Earth and Planetary Astrophysics
Impact of geometry on 1D molecular-kinetics simulations of acoustic-gravity wave propagation into the exosphere
Jose A. Perez Chavez, Orenthal J. Tucker, Shane R. Carberry Mogan et al. (+2 more)
Direct Simulation Monte Carlo (DSMC) calculations of acoustic
gravity wave propagation into the exobase region of a Mars-like atmosphere reveal that radial geometry can reduce wave-driven heating compared to a Cartesian model. We examine two acoustic wave (AW) modes with periods of 11 minutes (AW1) and 5.5 minutes (AW2) propagating from 100 to 320 km altitude using a radial molecular kinetics model. The wave-driven heating was reduced by 40-56% with cycle-averaged temperature gradient $\langle dT/dr \rangle$ decreasing from 9.4 K per scale height H0 to 5.6 K/H$_0$ for AW1 and from 4.4 K/H$_0$ to 1.9 K/H$_0$ for AW2 when accounting for planetary
curvature. While the growth in wave density amplitude was attenuated for the 1D radial geometry as well, the heating differences are more pronounced, with both effects driven by
geometric spreading accumulating as waves propagate into increasingly rarefied regions. These findings suggest that accounting for
curvature effects is crucial when conducting DSMC estimates of acoustic wave contributions to thermospheric heating and atmospheric escape, as Cartesian-based derived counterparts may be overestimated by factors of 1.7-2.3 for these frequencies.
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All authors Jose A. Perez Chavez, Orenthal J. Tucker, Shane R. Carberry Mogan, Robert E. Johnson, Christopher Blaszczak-Boxe
Astrophysics of Galaxies
Weighing the Milky Way's Satellite Galaxies Using Pulsar Accelerations
Thomas Donlon II, Sukanya Chakrabarti and Jason A. S. Hunt
The properties of
dwarf galaxies orbiting the Milky Way (MW) are useful for testing models of the formation of our
Galaxy, and by extension various theories of cosmology. Recent efforts to measure the masses of the MW's satellite
dwarf galaxies have relied on the motions and positions of
stars in the MW's disk and
halo, which are perturbed by the passage of satellite
galaxies. As there are many known processes in our
Galaxy that lead to observed disequilibrium in
stars, these kinematic methods have been limited by the inherent difficulty in identifying only the perturbations due to particular satellite
galaxies. We present a novel method for determining the masses of two MW satellite
galaxies – the Large Magellanic Cloud (LMC) and the Sagittarius
Dwarf Spheroidal
Galaxy (Sgr dSph) – using only direct, instantaneous acceleration data derived from extremely precise timing of millisecond
pulsars near the Sun. As the LMC and Sgr dSph orbit the MW, they cause wave-like distortions in the structure of the disk plus a large-scale offset in the centers of mass of the dark matter
halo and the baryonic disk. These two effects lead to asymmetric accelerations above and below the disk midplane near the Sun, which is observed in the
pulsar acceleration data. Notably, the amplitude of this asymmetry is shown to depend on the masses of the orbiting satellites. We analyze a grid of simulations with varying masses of each satellite. We find the total (dark +
baryon) mass enclosed within the
tidal radius at the present day for the LMC to be 4.1 $\pm$ 1.0 $\times$ 10$^{10}$ M$_\odot$ within a radius of 16.6 kpc, and for Sgr to be 3.5 $\pm$ 2.4 $\times$ 10$^8$ M$_\odot$ within a radius of 5 kpc. These results are generally consistent and competitive with previous determinations of the masses of these objects, but entirely independent of any
stellar kinematic data for the first time.
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Earth and Planetary Astrophysics
Diversity in the haziness and chemistry of temperate sub-Neptunes
Pierre-Alexis Roy, Björn Benneke, Marylou Fournier-Tondreau et al. (+17 more)
Recent transit observations of K2-18b and TOI-270d revealed strong molecular absorption signatures, lending credence to the idea that temperate sub-Neptunes (T$_\mathrm{eq}$=250-400K) have upper atmospheres mostly free of aerosols. These observations also indicated higher-than-expected CO$_2$ abundances on both
planets, implying bulk compositions with high water mass fractions. However, it remains unclear whether these findings hold true for all temperate sub-Neptunes. Here, we present the JWST NIRSpec/PRISM 0.7-5.4$\mathbf{\mu}$m transmission spectrum of a third temperate sub-Neptune, the 2.4R$_\oplus$
planet LP 791-18c (T$_\mathrm{eq}$=355K), which is even more favorable for atmospheric characterization thanks to its small M6 host
star. Intriguingly, despite LP 791-18c's radius, mass, and
equilibrium temperature being in between those of K2-18b and TOI-270d, we find a drastically different transmission spectrum. While we also detect methane on LP 791-18c, its transit spectrum is dominated by strong haze scattering and there is no discernible CO$_2$ absorption. Overall, we infer a deep metal-enriched atmosphere (246-415$\times$
solar) for LP 791-18c, with a CO$_2$-to-CH$_4$ ratio smaller than 0.07 (at 2$\sigma$), indicating less H$_2$O in the deep envelope of LP 791-18c and implying a relatively dry formation inside the water ice-line. These results show that sub-Neptunes that are near-analogues in density and temperature can show drastically different aerosols and envelope chemistry, and are intrinsically diverse beyond a simple temperature dependence.
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All authors Pierre-Alexis Roy, Björn Benneke, Marylou Fournier-Tondreau, Louis-Philippe Coulombe, Caroline Piaulet-Ghorayeb, David Lafrenière, Romain Allart, Nicolas B. Cowan, Lisa Dang, Doug Johnstone, Adam B. Langeveld, Stefan Pelletier, Michael Radica, Jake Taylor, Loïc Albert, René Doyon, Laura Flagg, Ray Jayawardhana, Ryan J. MacDonald, Jake D. Turner
Cosmology and Nongalactic Astrophysics
Inflation in light of ACT/SPT: A new perspective from Weyl gravity
Qing-Yang Wang
Recent measurements from the Atacama Cosmology
Telescope (ACT) and the South Pole
Telescope (SPT) have placed the strictest constraints on the
primordial scalar perturbation spectrum, reporting a spectral index of $n_s\sim0.967-0.98$ at 95% confidence level. This result indicates a stronger scale invariance of the scalar perturbation than earlier estimates, posing challenges for numerous inflation models. In this work, we propose a novel inflationary scenario based on Weyl scale-invariant
gravity, where the quadratic
curvature establishes the scale invariance of the scalar spectrum, while the higher-order extensions imprint the observed slight deviation. Specifically, the exponential
curvature extensions are introduced to suppress the mass divergence of the inflaton. We find such scenario naturally yields leading-order predictions of $n_s\simeq1-3/(2N)\sim0.97-0.975$ or $n_s\simeq1-5/(3N)\sim0.967-0.972$ for various models, in excellent agreement with the ACT/SPT constraints. This result builds a concrete bridge between theoretical and observational scale invariance, implying an enduring
cosmic echo of the
primordial symmetry.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Measuring the neutron star equation of state from EMRIs in dark matter environments with LISA
Theophanes K. Karydas and Gianfranco Bertone
Gravitational-wave observations of extreme mass-ratio inspirals (EMRIs) in
vacuum are largely insensitive to the internal structure of the small compact companion. We show that this conclusion can change when the central black hole is surrounded by a dense dark matter environment. We compute, for the first time, the relativistic dynamical-friction force on a
neutron star moving through a collisionless medium and its impact on the
evolution of EMRIs embedded in dense dark matter spikes. We then perform a
Bayesian parameter-estimation analysis of simulated LISA observations to assess the measurability of both spike properties and the companion's internal structure.We find that, in our fiducial dark matter spike models, EMRIs with signal-to-noise ratio (SNR) $\gtrsim 120$ can already distinguish
neutron star from black hole companions. At comparable signal-to-noise ratios, discrimination among
neutron star equations of state begins to emerge and becomes significantly stronger toward the high-SNR tail.
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Astrophysics of Galaxies
Resolving the ionizing photon budget crisis with JWST/NIRCam HII clumping constraints at z=6
Duncan Austin, Thomas Harvey, Christopher J. Conselice et al. (+18 more)
We present a comprehensive study of the ionizing properties of 1721
galaxies at $5.6<z<6.5$ using deep JWST/NIRCam photometric imaging from the NEP, JADES, and PRIMER surveys spanning an unmasked area $\sim550$arcmin$^2$ across UV magnitudes $-22\lesssim M_{\rm UV}\lesssim-17.5$. Our $90\%$
stellar mass complete sample suggests little relation of UV slope with magnitude, $\beta_{\rm UV}=(-0.040\pm0.022)M_{\rm UV}-2.88^{+0.43}_{-0.44}$, implying $f_{\rm esc}^{\rm LyC}\simeq5\%$ based on calibrations from the Low-
redshift Lyman Continuum Survey (LzLCS). We measure a constant ionizing
photon production efficiency with UV magnitude, $\log_{10}(\xi_{\rm ion, 0}/\rm Hz\,erg^{-1}) = -0.006^{+0.019}_{-0.017}~M_{\rm UV} + 25.05^{+0.39}_{-0.34}$, consistent with HST canonical values. The total production rate of
photons escaping into the IGM is computed as $\log_{10}(\dot{n}_{\rm ion}/\rm s^{-1}Mpc^{-3})=50.31^{+0.07}_{-0.06}$ for $M_{\rm UV}<-17$
galaxies from our
star forming and smouldering UV luminosity functions (UVLFs), which differ in the faint-end slope ($\alpha_{\rm SFG}=-2.2\pm0.2$; $\alpha_{\rm sm}=-1.7\pm0.2$). Extrapolating to the latest UVLF turnover limits from the massive
lensing galaxy cluster Abell S1063 ($M_{\rm UV, lim}=-13.5$) implies that a recombination-weighted HII clumping factor $C_{\rm HII, rec}=6.2^{+4.1}_{-2.1}$ is required to produce fully stably reionized at $z\simeq6$. A clumping factor of this magnitude resolves the ionizing
photon budget crisis. Our methodology paves the way for indirect clumping measurements from
galaxies which will provide insight into earlier stages of the EoR when the Ly$\alpha$-forest becomes saturated and more direct
quasar measurements become impossible.
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All authors Duncan Austin, Thomas Harvey, Christopher J. Conselice, Nathan J. Adams, Vadim Rusakov, Qiong Li, Lewi Westcott, Caio Goolsby, Kai Madgwick, James Arcidiacono, Massimo Ricotti, Sophie L. Newman, Louise T. C. Seeyave, James Trussler, Brenda Frye, Norman A. Grogin, Rolf A. Jansen, Anton M. Koekemoer, Nor Pirzkal, Michael Rutkowski, Rogier A. Windhorst
Astrophysics of Galaxies
Spectroscopic characterization of a remarkable temporally varying, triple-lensed quasar at z=2.67
Charlie Lind-Thomsen, Kasper E. Heintz, Albert Sneppen et al. (+5 more)
Gravitationally lensed
quasars are viable
cosmic tools for constraining a diversity of fundamental astrophysical phenomena; They enable identification of faint, low-mass supermassive black holes, provide unique constraints on the intervening intergalactic or interstellar medium in their sightlines, and can be used to determine key cosmological quantities such as the Hubble constant, $H_0$. However, they are rare phenomena, and it has proven difficult to define efficient, unbiased selection methods.} In this study, we report the independent spectroscopic identification of a remarkable triple-lensed
quasar at $z=2.67$, identified based on astrometric measurements from the
Gaia mission, previously identified in Pan-STARRS. Furthermore, a larger spectroscopic follow-up survey of
Gaia-detected candidate lensed
quasars. We characterize in detail the three mirror images of the
quasar and their spatial and temporal spectroscopic coverage, with focus on the emission-line properties which shows variation across sigthlines and temporal
evolution over the $\sim 11$months spectroscopic campaign. We construct a lens model of the foreground source from a combination of the multiple spectra and deep optical imaging, providing a robust
halo mass of $M_{\rm h} = (2.78 \pm 0.05)\times 10^{10}M_\odot$. Based on the lens model, the time delay between each sightline is translated into an intrinsic
quasar time, allowing us to construct a
quasar timeseries over $\sim18$months with monthly cadence. Over months timescales the broad emission lines vary in both velocity offset and equivalent width (EW) as well as an overall increase in ionization. This exemplary triple-lensed
quasars demonstrates the viability of identifying such rare lens configurations based purely on the astrometric measurements from the
Gaia mission, which we here provide optimized selection criteria for, for future studies.
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All authors Charlie Lind-Thomsen, Kasper E. Heintz, Albert Sneppen, Kostas Valeckas, Stefan Geier, Jens-Kristian Krogager, Johan Richard, Johan P.U. Fynbo
Cosmology and Nongalactic Astrophysics
On the validity of the continuity equation in a modified gravity framework with CMB, DES 3x2pt and tomographic ISW data
Ziad Sakr and Miguel Quartin
In this work we propose a phenomenological modification to the continuity equation at the linear perturbation level and test it using combinations of the CMB temperature, polarization and
lensing potential angular spectrum, the ISW-
galaxy cross power spectrum and the 3$\times$2pt
lensing and
galaxy clustering from DES survey. We investigate two parametrisations of this modification, both proportional to a new parameter $A_c$, which is assumed to be either constant in time, or proportional to the scale factor $a$, in order to be more relevant at late times. We find DES and ISW data to be consistent with the standard continuity equation when $A_c$ is constant, but 2–3$\sigma$ hints of a non-zero modification appear when Planck data is included. The model $A_c \propto a$ results in stronger tensions. We also test the effects of including the common extra parameters $\mu$ and $\eta$ that modify the Poisson equation and Weyl potential. Although $A_c$, $\mu$ and $\eta$ are correlated, we still find non-zero $A_c$ when Planck data is included or without Planck if $A_c \propto a$ and only either $\eta$ or $\mu$ are allowed to vary. We conclude that violations of the continuity equation should be considered with care when testing additional deviations from general relativity.
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Instrumentation and Methods for Astrophysics
Reaching diffraction-limited localization with coherent PTAs
Anna C. Tsai, Dylan L. Jow and Ue-Li Pen
Current
pulsar timing array (PTA) analyses do not take full advantage of
pulsar distance information, thereby missing out on improved angular resolution and on a potential factor-of-two gain in detection sensitivity for individual gravitational-wave (GW) sources. In this work, we investigate the impact of precise
pulsar distance measurements on angular resolution as an extension to previous work measuring the angular resolution of a dense, isotropic PTA [Jow et al., 2025]. We present a coherent map-making technique that utilizes precise
pulsar distance measurements to reach the diffraction-limited resolution of an individual source: $\delta \theta_{\mathrm{diff}} \sim (1/\mathrm{SNR})(\lambda_{\mathrm{GW}}/r) \approx 2~\mathrm{arcmin}$, where the SNR refers to the detection strength of the source. With this level of angular resolution, identifying an EM counterpart may become feasible, enabling multi-messenger follow-up. We show that for $\rm SNR=10$, which may be the current sensitivity level using a coherent analysis, the diffraction limit is reached with roughly 9
pulsars. Moreover, angular resolution scales sharply with the number of known
pulsar distances as $\sim (1/\mathrm{SNR})^{N_{\mathrm{dist}}/2}$. Thus, each additional
pulsar with high signal-to-noise timing and precise distance measurement can improve PTA resolution by an order of magnitude. The distance to the best-timed millisecond
pulsar (PSR J0437$-$4715) is already constrained to sub-parsec levels. We argue, therefore, that a coherent analysis of PTA data, fully incorporating
pulsar distance information, is timely.
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Astrophysics of Galaxies
Pressure and Star Formation in LITTLE THINGS Dwarf Irregular Galaxies
Bruce G. Elmegreen, Deidre A. Hunter and Edvige Corbelli
The surface densities of
star formation, Sigma_SFR, in 24
dwarf irregular (dIrr)
galaxies from the LITTLE THINGS survey are combined with gas surface densities and midplane pressures to examine the correlations found previously for spiral
galaxies. The pressure is the weight of the disk inside the gas layer, including gas,
stars, and dark matter, which usually dominates disk
gravity in dIrrs. We compare the results to the outer part of M33, which has similar local properties but a slightly higher
metallicity, enabling the detection of CO. All the data are convolved to the HI beam, but to study the effects of resolution, the
galaxies are examined first with average radial profiles, and then with maps having 1.5" pixels and 244 pc pixels. The correlations are found to be independent of resolution from 24 pc to 424 pc. The average ratio of molecular to atomic surface density is estimated to be 0.23+-0.1, from the H_2 surface density in M33 compared to the HI surface density at the same Sigma_SFR in the dIrrs. With this ratio, the average
star formation rate per molecule is about the same for all the dIrrs, and a factor of 2 less than the rate in M33. The pressure in dIrrs is so low that CO is essentially a dense gas tracer, with the same surface density threshold at the low
metallicities of dIrrs as HCN has in spiral
galaxies. As a result, CO regions in dIrrs should be strongly self-gravitating.
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Astrophysics of Galaxies
Chemical enrichment in LINERs from MaNGA. II. Characterizing the shape of their radial metallicity gradients
Borja Pérez-Díaz, José M. Vílchez, Enrique Pérez Montero et al. (+3 more)
Chemical abundance radial gradients provide key information on how the processes that affect chemical enrichment of the gas-phase interstellar medium (ISM) act at different
galaxy scales. Whereas in the last decades there has been an increase in the number of
galaxies studied with integral field spectroscopy, there is still not a clear picture on a subsequent characterization of the chemical abundance radial gradients in
galaxies hosting Active
Galactic Nuclei (AGNs). This lack of analysis is even more accentuated in the case of low-ionization
nuclear emission-line regions (LINERs). For the first time, we analyze the chemical abundance radial gradients in a sample of LINER-like
galaxies, whose
nuclear emission has been previously (Paper I) discussed. We use a sample of 97
galaxies from the Mapping Nearby
Galaxies at Apache Point Observatory (MaNGA), whose
nuclear regions show LINER-like emission. We use the open-source code HII-CHI-Mistry to estimate the chemical abundance ratios 12+log(O/H) and log(N/O) in the HII regions across the disks in our sample, as well as in the
nuclear parts where the LINER-like activity dominates. To fit the radial profiles we use a piecewise methodology which uses a non-fixed number of breaks to find the best fit for the data. We obtain that majority of our sample of
galaxies exhibits departures from the single linear gradient both in 12+log(O/H) and log(N/O) (as expected from the inside-out scenario). We investigate whether these departures are driven by
galaxy properties (
stellar mass, neutral gas mass,
stellar velocity dispersion), finding not correlation at all. We also report that in most cases there is no correlation between the shape of the 12+log(O/H) and log(N/O) radial profiles. We propose a model in which AGN (feed)back, acting at different scales depending on the
galaxy and its evolutionary stage, might be responsible for these departures.
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All authors Borja Pérez-Díaz, José M. Vílchez, Enrique Pérez Montero, Igor A. Zinchenko, Brian Tapia-Contreras, Patricia B. Tissera
Astrophysics of Galaxies
Hidden No More: Spotlight on tidal disruption events in active galactic nuclei
Patrik Milán Veres
Tidal disruption events (TDEs) are typically discovered in previously quiescent
galaxies. However, earlier studies have revealed a handful of TDEs occurring in pre-existing active
galactic nuclei (AGNs). We discuss AT2019aalc, a promising TDE candidate in an AGN, and compare it to similar sources. We also explore Bowen fluorescence
flares, a newly identified class of flaring supermassive black holes, as potential members of the TDE in AGN transient class. We aim to connect the observed properties of these
flares with the expectations of TDE-in-AGN simulations.
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Cosmology and Nongalactic Astrophysics
Applying the BF method on the DESI evidence for dynamical dark energy models
Ziad Sakr
Recent
baryon acoustic oscillation measurements from the DESI, when combined with CMB data and Type Ia
supernovae observations, indicate a preference for dynamical dark energy when considering the Chevallier-Polarski-Linder (CPL) model, over the standard {\Lambda}CDM or the wCDM model. However, the Bayes factor, a key metric for model comparison, remains inconclusive on which model is preferred. This paper applies the BF method, that integrates both
Bayesian and frequentist approaches to DESI data to address the limitations of purely frequentist or
Bayesian methods. It consists in considering the Bayes factor as a random variable and calculates its distribution, that results from values computed in a frequentist approach after perturbing the data following the model considered. We apply this hybrid method to DESI data, comparing the CPL and w models under various prior conditions, including weak and strong priors, and theory-informed priors. We find that, when the traditional bayes factor is considered, that weak priors favor the w model over CPL, while strong priors favor CPL. Additionally, theory-informed priors further enhance the preference for the w model. While when we apply the BF method, the preference for CPL over w is seen in all cases albeit with similar but reduced impact on the p-value from the different prior considerations. We also tried to generalize further, by perturbing as well the covariance
matrix following the model considered, and found that, in general, the current data in that case is not stringent enough to disentangle between the two models. Our results demonstrate that varying the Bayes factor as a random variable, providing that the covariance
matrix is kept as model independent, provides a robust model comparison, reducing the impact of prior dependence as well as offering quantitative assessment of the preferences of the competing models.(abridged)
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Earth and Planetary Astrophysics
A "New Hope" for Moon Formation: Presenting a Multiple Impact Pathway
Harrison Davies, Philip J. Carter, Louis Eddershaw et al. (+2 more)
The leading hypothesis for the origin of the Moon, that of a single
giant impact, faces significant challenges. These include either the need for an impactor with a near-identical composition to Earth or an extremely high-mass or high-energy impact to achieve near-complete material mixing. In this paper we explore an alternative, the "multiple impact hypothesis", which relaxes the compositional constraints on both the target and projectile, and allows for the consideration of more probable, less extreme impacts that steadily grow the Earth and Moon to their current size over several impact events. Using the hydrodynamical code SWIFT, we simulate "chains" of impacts and follow the growth of a moon around a
planet analogous to our own. Our results demonstrate that chains of three or more impacts can produce systems comparable to the Earth-Moon system whilst achieving higher compositional similarities than the canonical
giant impact scenario. This presents the multiple impact hypothesis as a promising alternative to the single large impact scenario for the origin of the Moon.
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All authors Harrison Davies, Philip J. Carter, Louis Eddershaw, Jingyao Dou, Zoë M. Leinhardt
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Exploring New Propagation Scales With Galactic Neutrinos
Miller MacDonald, Kiara Carloni, Carlos A. Argüelles et al. (+2 more)
The recent observation of high-energy
Galactic neutrinos by IceCube allows for searches of new physics affecting
neutrino propagation on scales of $O(10^9-10^{15})\,\mathrm{km/GeV}$ in distance over energy. We assess the sensitivity of upcoming measurements of
Galactic neutrinos by IceCube and KM3NeT to such new phenomena. We focus on two scenarios: quasi-Dirac
neutrinos and
neutrino decays. In the quasi-Dirac scenario, we find that joint measurements by IceCube and KM3NeT are sensitive to the mass-squared differences $\delta m^2 \in \left(10^{-13.6}~\mathrm{eV^2}, 10^{-12.3}~\mathrm{eV^2}\right)$ at the $90\%$ confidence level. For
neutrino decays, the same measurements are sensitive to mass over lifetime ratios $m / \tau > 10^{-12.8}~\mathrm{eV^2}$ at the same significance. Our results demonstrate that measurements of
Galactic neutrinos by a global network of
neutrino telescopes can probe signatures of
neutrino mass models.
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All authors Miller MacDonald, Kiara Carloni, Carlos A. Argüelles, Ivan Martínez-Soler, Rafael Alves Batista
Cosmology and Nongalactic Astrophysics
Model independent approach towards measuring expansion and growth factor from next generation galaxy clustering and lensing angular power spectrum
Ziad Sakr
In this work we perform Fisher forecasts on the expansion and the growth factors following model independent approaches from 3x2pt joint analysis of the
galaxy lensing, clustering, and their cross-correlated spectra at the linear, and extending as well to non linear scales. For that, instead of choosing a specific model for the matter power spectrum, the main ingredient of these probes, we express it by parametrizing its components, such as the expansion and the growth factor, and those of the standard
halo model and excursion set theory in several z bins, besides to the different bias and non-linear bias modelling functions. We apply the technique to Euclid, Rubin and SKA public specifications in the range 0.2 < z < 1.8 and show that one can then obtain model-independent constraints of the expansion E(z i ) and the growth factor G(z i ). We also show the change in gain in precision at each z- shell when going from pessimistic cut at linear scales to more optimistic non-linear settings, or the difference between using each survey alone or a combination of all of them, or the impact from fixing or adding more degrees of freedom in the non-linear modeling. We found that, in the most agnostic case, one can still reach high precision on E(z i ) in the order of the percent level when combining the three surveys at once while the growth factor G(z i ) has for the same settings one order of magnitude weaker constraints. We also found for both factors, an improvement that can reach one order of magnitude in precision when passing from linear to non-linear scales. We conclude that we will be able to constrain the two important factors of the background
evolution and structure formation of the Universe when using non linear scales and the combined power of future surveys even in the most agnostic approaches.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Two-Dimensional Pulsar Distance Inference from Nanohertz Gravitational Waves
Si-Ren Xiao, Ji-Yu Song, Yue Shao et al. (+3 more)
Pulsar timing arrays (PTAs) are limited in localizing nanohertz continuous gravitational waves (CGWs) by uncertainties in
pulsar distances. We introduce a method to infer
pulsar distances in two dimensions, using phase information from the
pulsar terms of multiple CGW sources. Our approach can enhance distance precision and, in some cases, achieve order-of-magnitude improvements relative to existing one-dimensional distance-inference methods. Using simulations of an SKA-era PTA with realistic parallax-based distance priors, we demonstrate that
pulsars at $\sim 1$ kpc can achieve sub-parsec distance precision with only a few CGW sources. Such improvements in
pulsar-distance precision have important implications for CGW host-
galaxy identification and multimessenger observational prospects.
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All authors Si-Ren Xiao, Ji-Yu Song, Yue Shao, Ling-Feng Wang, Jing-Fei Zhang, Xin Zhang
High Energy Astrophysical Phenomena
Constraints on the Population of Common Sources of Gravitational Waves and High-Energy Neutrinos with IceCube During the Third Observing Run of the LIGO and Virgo Detectors
Doğa Veske, Zsuzsa Márka and Albert Zhang
The discovery of joint sources of high-energy
neutrinos and gravitational waves has been a primary target for the LIGO, Virgo, KAGRA, and IceCube observatories. The joint detection of high-energy
neutrinos and gravitational waves would provide insight into
cosmic processes, such as progenitor dynamics and
outflows. The joint detection of multiple
cosmic messengers can also elevate the significance of the observation when some or all of the constituent messengers are sub-threshold, not significant enough to declare their detection individually. Leveraging data from the LIGO, Virgo, and IceCube observatories, we conducted an archival investigation of sub-threshold multimessenger events. Complementing previous analyses, we used minimal assumptions to search for common sources of sub-threshold gravitational-wave and high-energy
neutrino candidates during the third observing run (O3) of the Advanced LIGO and Advanced Virgo detectors. Our search did not identify significant joint sources. We therefore derive constraints on the rate density of joint sources for each compact binary merger population as a function of the energy emitted in
neutrinos. Only a fraction of the gravitational-wave sources emit
neutrinos, if the
neutrino emission has high bolometric energy ($>10^{52}$ to $10^{54}$ erg).
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High Energy Astrophysical Phenomena
Can accreting isolated neutron stars be detected?
Marina Afonina, Anton Biryukov and Sergei Popov
We perform population synthesis modeling of isolated
neutron stars in the Milky Way over its lifetime. Compared with previous studies, we use more detailed models of the interstellar medium and the magneto-rotational
evolution of
neutron stars. We demonstrate that presently, the
spin-down rate at the propeller stage is the main uncertain factor that influences the number of accreting isolated
neutron stars. If the propeller stage duration allows
neutron stars to begin accreting matter from the interstellar medium and if the efficiency of
accretion is high, then the number of accreting isolated
neutron stars in eROSITA data can reach ~a few thousand. Still, uncertainties in
spin-down at the propeller stage and in the
accretion process can drastically decrease this number. We suggest that future observations of
neutron stars in wide low-mass binaries recently discovered by
Gaia can clarify these issues.
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Astrophysics of Galaxies
OutLines: Modeling Spectral Lines from Winds, Bubbles, and Outflows
Sophia R. Flury
Studies of kinematics and geometry of outflowing gas rely on modeling features in integrated spectra using empirical
quantiles or fitting multiple Gaussian or Voigt profiles. Such methods can miss key underlying physics and even lead to spurious interpretations of observations. To address this problem, we present the public python code OutLines, which predicts spectral emission and absorption line profiles produced by winds, bubbles, and
outflows. By design, OutLines is phenomenologically and scale agnostic to bridge the gap between observations and simulations across a broad swath of astrophysics. The OutLines code accounts for differences in velocity field, density profile, and
outflow geometries, making OutLines versatile for a wide variety of astrophysical phenomena. We demonstrate the wide applicability of OutLines by using the code to model line profiles in an H II region
knot, super
star clusters, a starburst
galaxy, and an AGN. In each of these contexts, we illustrate how OutLines can illuminate key underlying physics in ways that improve scientific understanding and address important open questions in astronomy, including the key mechanisms in the
baryon cycle, the
evolution of H II regions and
galaxies, and even Lyman continuum escape. OutLines will be a critical resource as massively multiplexed spectroscopic surveys with facilities like WEAVE and 4MOST come online, providing the means to probe feedback with deeper, higher resolution spectroscopy for unprecedented large samples of objects.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Subtracting compact binary foregrounds utilizing anisotropic statistic for third-generation gravitational-wave detectors
Soichiro Kuwahara, Atsushi Nishizawa and Lorenzo Valbusa Dall'Armi
The astrophysical foreground from compact-binary coalescence signals is expected to be a dominant part of total gravitational wave (GW) energy density in the frequency band of the third-generation detectors. The detection of any other subdominant
stochastic GW background (GWB), especially a
primordial GWB, will be disturbed by the astrophysical foreground, which needs to be cleaned for further studies of other
stochastic GWB. Although previous studies have proposed several cleaning methods, the foreground from subthreshold binary
neutron stars (BNS) has been a major obstacle to remove. In this paper, we propose the novel idea to acquire better estimation of the unresolved foreground, by using the information about its anisotropies. We simulate the BNS population and compute its angular power spectrum and shot noise. We find that the shot noise from BNS is too faint to observe after subtracting loud signals due to the limited angular resolution of the third-generation detectors. This justifies the approximation regarding the unresolved foreground as an isotropic component. We also discuss the angular resolution necessary to make our method valid for the foreground subtraction.
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Astrophysics of Galaxies
Stellar masses and mass ratios for Gaia open cluster members
Sagar Malhotra, Alfred Castro-Ginard, Friedrich Anders et al. (+7 more)
Context: Unresolved binaries in
star clusters can bias
stellar and cluster mass estimates, making their proper treatment essential for studying cluster dynamics and
evolution. Aims: We aim to develop a fast and robust framework for jointly deriving
stellar masses and multiplicity statistics of member
stars, together with optimal cluster parameters. Methods: We use
Gaia DR3 parallaxes together with multi-band photometry of open cluster (OC) members to infer
stellar masses and binary mass-ratios through simulation-based inference (SBI), while iteratively fitting the cluster parameters. The validation of our SBI framework on simulated clusters demonstrates that the inclusion of infrared photometry significantly improves the detection of low mass-ratio binaries. The minimum mass-ratio threshold for reliably identifying unresolved binaries depends on cluster properties and the available photometry, but typically lies below $q=0.5$. Results: Applying our method to 42 well-populated OCs, we derive a catalogue of
stellar masses and mass-ratios for 27201
stars, achieving typical uncertainties of 0.08 in $q$ and $0.01\,\mathrm{M}_\odot$ in the primary
stellar mass. We analyse the archetype OCs M67 and NGC 2360 in detail, including mass segregation and mass-ratio distribution among other characteristics, while deriving multiplicity fractions for the rest of the sample. We find evidence that the high mass-ratio ($q\geq 0.6$) binary fraction shows a strong correlation with the age and a weak anti-correlation with the cluster
metallicity. Furthermore, the variation of the binary fraction with
stellar mass in OCs shows strong accordance with the observed dependence for field
stars heavier than $\gtrsim0.6\,\mathrm{M}_\odot$. Conclusions: Our work paves a path for future population-level investigations of multiplicity statistics and precision
stellar masses in extended samples of OCs.
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All authors Sagar Malhotra, Alfred Castro-Ginard, Friedrich Anders, Carme Jordi, Judit Donada, Xavier Luri, Lola Balaguer-Núñez, Songmei Qin, Yueyue Jiang, Andrija Župić