Cosmology and Nongalactic Astrophysics · Cross-listed from physics.hist-ph
The 59th Karl Jansky Lecture: Discovering the Radio Universe
K. I. Kellermann
The NRAO 59th Karl Jansky Lecture was presented on 24 October 2024, 22 November 2024, and 4 December 2024 in Charlottesville, Virginia, Socorro, New Mexico, and Green Bank, West Virginia, respectively. The lecture covered the circumstances of the author's start in
radio astronomy, the demographics of
radio astronomers, discussions of the outstanding, mostly serendipitous, discoveries made by
radio astronomers over the past century, and concluded with reflections on the prospects for further new discoveries.
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Solar and Stellar Astrophysics
A study of transients from ground-based surveys reveals new ultra-compact accreting white dwarf binaries
Jan Kára, Liliana Rivera Sandoval, Wendy Mendoza et al. (+5 more)
AM CVn
stars are ultra-compact semi-detached binaries consisting of a white
dwarf primary and a hydrogen-depleted secondary. In this paper we present spectroscopic and photometric results of 15 transient sources pre-classified as AM CVn candidates. Our analysis confirms 9 systems of the type AM CVn, 3 hydrogen-rich cataclysmic variables (accreting white
dwarfs with near-main-sequence
stars for donors) and 3 systems that could be evolved cataclysmic variables. Eight of the AM CVn
stars are analysed spectroscopically for the first time, which increases the number of spectroscopically confirmed AM CVns by about $10\%$. TESS data revealed the orbital period of the AM CVn
star ASASSN-20pv to be $P_\mathrm{orb}=27.282\,\mathrm{min}$, which helps to constrain the possible values of its mass ratio. TESS also helped to determine the superhump periods of one AM CVn
star (ASASSN-19ct, $P_\mathrm{sh}=30.94\,\mathrm{min}$) and two cataclysmic variables we classify as WZ Sge
stars ($P_\mathrm{sh}=90.77\,\mathrm{min}$ for ZTF18aaaasnn and $P_\mathrm{sh}=91.6\,\mathrm{min}$ for ASASSN-15na). We identified very different abundances in the spectra of the AM CVns binaries ASASSN-15kf and ASASSN-20pv (both $P_\mathrm{orb}\sim 27.5$ min), suggesting different type of donors. Six of the studied AM CVns are X-ray sources, which helped to determine their mass
accretion rates. Photometry shows that the duration of all the superoutbursts detected in the AM CVns is consistent with expectations from the disc instability model. Finally, we provide refined criteria for the identification of new systems using all-sky surveys such as LSST.
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All authors Jan Kára, Liliana Rivera Sandoval, Wendy Mendoza, Thomas J. Maccarone, Manuel Pichardo Marcano, Luis E. Salazar Manzano, Ryan J. Oelkers, Jan van Roestel
Earth and Planetary Astrophysics
A Comprehensive Analysis of the Panchromatic Transmission Spectrum of the Hot-Saturn WASP-96 b: Nondetection of Haze, Possible Sodium Limb Asymmetry, Stellar Characterization, and Formation History
Le-Chris Wang, Zafar Rustamkulov, David K. Sing et al. (+4 more)
We conduct a reanalysis of the JWST NIRISS/SOSS observation of the hot-Saturn WASP-96 b. Initial analysis of this data revealed an enhanced Rayleigh scattering slope at the blue end of the transmission spectrum, suggesting the presence of hazes at high altitudes. In this work, we report non-detection of this slope, confirming an atmosphere clear of high-altitude aerosols consistent with the pre-JWST results. Also contrary to the initial result, our results indicate the presence of gray cloud deck, although at relatively low altitudes/high pressures. We further combined the NIRISS/SOSS spectrum with VLT, HST, and Spitzer to produce a transmission spectrum from 0.35 $\mu$m to 5 $\mu$m. We constrain the mass fraction of multiple chemical species, including: H$_2$O$=-2.62^{+0.43}_{-0.42}$, K$=-5.76^{+1.05}_{-1.13}$, and Na$=-3.40^{+0.90}_{-0.92}$. C/O ratio and
metallicity are tentatively constrained at substellar values (C/O$_{planet}=0.57^{+0.07}_{-0.12}$ and [Fe/H]$_{planet}=0.01^{+0.46}_{-0.52}$ compared to C/O$_{star}=0.92\pm0.25$ and [Fe/H]$_{star}=0.24\pm0.05$). Inputing these composition constraints to interior models, we constrain a core mass of $43^{+8}_{-15}$ M$_\oplus$. This, in addition to our inferred super-
stellar refractory-to-oxygen ratio ($\Delta\log_{10}(R/O)=1.48^{+0.57}_{-0.62}$) and substellar C/O ratio, suggests that the core of WASP-96 b likely formed outside of water iceline, underwent disk-driven migration, and accreted its atmosphere inside the carbon soot line. We find evidence of atmospheric leading-trailing terminator asymmetries in the broadened sodium absorption feature with a transit time offset of 50 seconds, while the water features appear symmetric. CH$_4$, CO, and CO$_2$ remain unconstrained due to spectral coverage limits. Upcoming JWST NIRSpec/G395H observations (ID 4082, PI: M. Radica) will be crucial for constraining these carbon-bearing species.
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All authors Le-Chris Wang, Zafar Rustamkulov, David K. Sing, Joshua Lothringer, Patrick McCreery, Daniel Thorngren, Munazza K. Alam
Earth and Planetary Astrophysics
Dynamical fractalization of ring systems
Jeremías Ruta, Nicolás Grandi and Tobías Canavesi
We develop an effective model to describe the dynamics of a system of particle moving in circular configurations around a central mass, by considering the continuum limit of the angular distribution, to obtain the stable configurations for different initial parameters. We compute the resulting fractal dimension and compare it with that of a statistical Cantor ring system.
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High Energy Astrophysical Phenomena
The nature of UHE source 1LHAASO J1740+0948u and its connection to PSR J1740+1000
Seth Gagnon, Yichao Lin, Alexander Lange et al. (+4 more)
We present multi-wavelength analysis of 1LHAASO J1740+0948u and its surroundings including the
pulsar wind nebula of middle-aged
pulsar PSR J1740+1000. Although a dozen X-ray sources are found within the UHE emission site, careful analysis shows that they are unlikely to produce the observed UHE emission. The most likely particle accelerator is
pulsar J1740+1000 which if offset by 13' north of the UHE source but appears to be connected to it by an extended feature seen in X-rays. For a plausible
pulsar distance of 1.2 kpc, 1LHAASO J1740+0948u must be located about 5 pc away which requires rapid transport of electrons along the feature to avoid radiative losses. This poses several challenges for standard
pulsar theory. Firstly, being produced $\lesssim$ 10 kyrs ago, particles must have been accelerated to the energy corresponding to a large fraction of the
pulsar's full potential drop across the polar cap. Secondly, due to the lack of TeV emission extension toward the
pulsar, particles must be accumulating in the UHE region. In this context, we discuss two possible scenarios: a tail filled with
pulsar wind and confined by the bow-shock due to the fast
pulsar's motion and an ISM filament filled by the most energetic
pulsar wind particles escaping from the apex of the bow-shock.
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All authors Seth Gagnon, Yichao Lin, Alexander Lange, Hui Yang, Noel Klingler, Jeremy Hare, Oleg Kargaltsev
Solar and Stellar Astrophysics
Ionizing radiation of [WR] stars: atmospheres and photoionization models
L.V. Da Conceição, W.LF. Marcolino and V. Maria
The radiation field of central
stars of planetary nebulae (CSPNe) is crucial for determining the physical conditions of planetary nebulae (PNe). Many studies in the literature model PNe using the blackbody approximation (bb) or plane-parallel (p-p) atmospheres as the ionizing source. However, these approaches become inconsistent when the central
star is a Wolf-Rayet ([WR]) type. These objects are hydrogen-deficient and exhibit intense
stellar winds, similar to classical massive WR
stars. Their accurate description therefore requires sophisticated NLTE expanding atmosphere models. In this work, we selected [WR] NLTE expanding-atmosphere models spanning a range of temperatures and mass-loss rates and compared them with bb and p-p models. We examined differences in the spectral energy distribution and ionizing
photon fluxes for H I, He I, and He II to assess the impact of
stellar winds on the nebula-
star interaction. Using CLOUDY, we also evaluated how each ionizing source affects predicted line ratios (I$_{\lambda}$/I$_{\beta}$) for a sample of PNe with [WR]
nuclei. Model performance was measured through the rms deviation between observed and predicted ratios. For temperatures below 100,000 K, the EUV spectrum differs strongly among the three model types.
Stellar winds introduce substantial opacity, reducing log Q(He II) significantly relative to no-wind models. For hotter [WR]
stars, wind effects on ionizing fluxes are much smaller. For nebulae hosting late-type [WR]
stars, models including winds provide much better agreement with observed line ratios than bb or p-p models, whereas for early-type
stars the choice of ionizing source has only a minor influence. Our results indicate that bb and p-p approximations should be avoided when modelling PNe with [WR] central
stars, especially those of the [WCL] subtype, because they fail to reproduce the strong wind-modified ionizing spectra.
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High Energy Astrophysical Phenomena
An Investigation of Systematic Effects from Background Priors on PSR J0740$+$6620 Radius Estimates using Synthetic NICER and XMM-Newton Data
Isiah M. Holt, M. Coleman Miller, Alexander J. Dittmann et al. (+1 more)
Accurate and precise measurements of
neutron star radii provide invaluable information about the cold, dense matter in
neutron star cores. Analyses of synthetic X-ray pulse waveform data similar to the data obtained from non-accreting
neutron stars using the
Neutron star Interior Composition Explorer (NICER) have indicated that mass and radius estimates made using such data are robust against some systematic errors that may be made when modeling these data, such as errors in the assumed pattern of the thermal X-ray emission from the surface of these
stars. A potentially important but so far unexplored source of systematic error is misparameterization of unmodulated background components, which can bias the inferred radius, particularly when data from different
telescopes are used in the analysis. In this study, we investigate the effects of the background model on radius estimates by jointly analyzing synthetic NICER and XMM-Newton data, using the $\sim 2.1~M_\odot$
pulsar PSR~J0740$+$6620 as a prototypical example. Our analysis shows that even if the background assumed in the model underestimates the actual background by a factor of more than five, the resulting shift of the radius posterior from the true value of the radius corresponds to only $\sim1\sigma$. In all the cases we examined, the
Bayesian evidence for the correct background model is greater than for the incorrect background model. These results add to the evidence that analyses of NICER-like data provide accurate measurements of
neutron star radii when the statistical sampling is thorough and the model fits the data well.
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All authors Isiah M. Holt, M. Coleman Miller, Alexander J. Dittmann, Frederick K. Lamb
High Energy Astrophysical Phenomena
David Calvert, Michael Redle, Bibek Gautam et al. (+4 more)
It is understood in a general sense that turbulent fluid motion below the shock front in a core-collapse
supernova stiffens the effective equation of state of the fluid and aids in the revival of the explosion. However, when one wishes to be precise and quantify the amount of
turbulence in a
supernova simulation, one immediately encounters the problem that
turbulence is difficult to define and measure. Using the 3D magnetohydrodynamic code ELEPHANT, we study how different definitions of
turbulence change one's conclusions about the amount of
turbulence in a
supernova and the extent to which it helps the explosion. We find that, while all the definitions of
turbulence we use lead to a qualitatively similar growth pattern over time of the turbulent kinetic energy in the gain region, the total amount of turbulent kinetic energy, and especially the ratios of turbulent to total kinetic energy, distinguish them. Some of the definitions appear to indicate
turbulence is a necessary contributor to the explosion, and others indicate it is not. The different definitions also produce
turbulence maps with different correlations with maps of the enstrophy, a quantity widely regarded as also indicating the presence of
turbulence. We also compute the turbulent adiabatic index and observe that in regions of low enstrophy, this quantity is sensitive to the definition used. As a consequence, the effective adiabatic index depends upon the method used to measure the
turbulence and thus alter one's conclusions regarding the impact of
turbulence within the
supernova.
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All authors David Calvert, Michael Redle, Bibek Gautam, Charles J. Stapleford, Carla Fröhlich, James P. Kneller, Matthias Liebendorfer
Instrumentation and Methods for Astrophysics
Data-Driven Stellar Spectral Modelling with GSPICE
Douglas P. Finkbeiner, Joshua S. Speagle and Tanveer Karim
Spectral data reduction pipelines deal with a wide variety of challenges including masking
cosmic rays, calibrating wavelength solutions, and estimating background noise while trying to remain model-agnostic. Traditional methods rely on hardware-specific code or pre-calculated
stellar model templates to solve this problem, making them model-dependent and not suitable for large
datasets that may contain new classes of objects. To solve this problem, we present a flexible, data-driven method: the GausSian PIxelwise Conditional
Estimator (GSPICE) that models an ensemble of spectra as a multivariate Gaussian and estimates the expected value and expected variance of each pixel in each spectrum conditional on others. GSPICE compares observed fluxes and errors to its own flux and error estimates to reveal outliers, which then can be completely masked or replaced by their estimates. We apply GSPICE to 3.9 million
stellar spectra from the LAMOST survey, and show that variations of the method can directly identify and correct both individual pixel-level outliers (e.g., from
cosmic ray hits) as well as extended systematic features (e.g., from incorrect wavelength calibrations), while still providing a novel characterization of the true per-pixel measurement uncertainties. We also demonstrate how GSPICE can take advantage of data partitioning with an application to diffuse interstellar bands. Implementations of GSPICE in both Python and IDL can be found here http://github.com/dfink/gspice.
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Astrophysics of Galaxies
The ViSta method for stacking in the Fourier domain and its application to the dusty star-forming galaxies in the ALMA Science Archive
Martina Torsello, Marcella Massardi, Elisabetta Liuzzo et al. (+3 more)
We present ViSta, a Visibility Stacking method to combine interferometric observations in the
Fourier domain at
radio to sub-millimeter wavelengths for
galaxies. The goal of our method is to maximize the exploitation of available archival interferometric data. By stacking visibilities of
galaxies with secure spectroscopic
redshifts directly in the
Fourier domain and transforming them into the rest-frame, we can enhance the stacked signal, suppress noise, and improve image reconstruction thanks to an extended coverage of the visibility domain. The ViSta method is highly flexible, allowing stacking of visibilities regardless of the array configuration or spectral setup. It is effective for both targeted sources and spurious detections offset from the phase center, whether unresolved or extended, within the field of view of the
telescope. We validated the method using simulated interferometric
datasets. For point-like sources, we can reconstruct the true emission with approximately 90% accuracy, obtaining similar results to classical image-plane stacking. In contrast, for faint and extended sources below the noise level, our method can provide a more accurate estimate of the signal compared to traditional image-based approaches. Finally, we applied ViSta to a sample of dusty
star-forming
galaxies (DSFGs) observed with the Atacama Large Millimeter/sub-millimeter Array (ALMA) to detect the CO(3-2) emission line. As for the simulated case, we demonstrated that our tool performs better than image-plane stacking when the signal from individual sources is no longer easily detectable, achieving higher SNR. Finally, we outline potential future applications of this stacking approach.
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All authors Martina Torsello, Marcella Massardi, Elisabetta Liuzzo, Gayathri Gururajan, Francesca Perrotta, Andrea Lapi
Astrophysics of Galaxies
Finding He II: Testing Novel Models of Binary Populations across Cosmic Time
Beryl Hovis-Afflerbach, Allison L. Strom, Alberto Saldana-Lopez et al. (+1 more)
Our understanding of massive
stars remains incomplete. Many high-z
galaxies and nearby analogs exhibit strong He II emission, indicating an abundance of
photons with energies >54.4 eV that standard single-
star population models cannot explain. Recent studies show that binary
evolution and non-
solar abundance patterns are required to explain the distinct spectra of high-z
galaxies observed by JWST. However, treatments of these properties vary drastically between models. We present the first results from a comparison of models with different treatments of binaries, including BPASS and novel stripped
star models, with rest-UV-optical spectra of high-z
galaxies' local analogs. This type of investigation can provide insights into which aspects of binary
evolution are important to reproduce observations and identify priorities in ongoing efforts to improve models. By constraining the properties of massive
stars at high
redshift, we can learn about the processes at play in high-z
galaxies and massive
star evolution more broadly.
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All authors Beryl Hovis-Afflerbach, Allison L. Strom, Alberto Saldana-Lopez, Sophia R. Flury
Instrumentation and Methods for Astrophysics
CLAWDIA: A dictionary learning framework for gravitational-wave data analysis
Miquel Llorens-Monteagudo, Alejandro Torres-Forné and José A. Font
Deep-learning methods are becoming increasingly important in gravitational-wave data analysis, yet their performance often relies on large training
datasets and models whose internal representations are difficult to interpret. Sparse dictionary learning (SDL) offers a complementary approach: it performs well in scarce-data regimes and yields physically interpretable representations of gravitational-wave morphology. Here we present CLAWDIA (Comprehensive Library for the Analysis of Waves via Dictionary-based
Algorithms), an open-source Python framework that integrates SDL-based denoising and classification under realistic detector noise. We systematise previously isolated SDL workflows into a unified, modular environment with a consistent, user-friendly interface. The current release provides several time-domain denoising strategies based on LASSO-regularised sparse coding and a classifier based on Low-Rank Shared Dictionary Learning. A companion toolbox, GWADAMA, supports
dataset construction and realistic conditioning of real and simulated interferometer data. We demonstrate CLAWDIA's performance by denoising the signal from binary
neutron star event GW170817 and by classifying families of instrumental glitches from LIGO's third observing run, highlighting robustness at low signal-to-noise ratios. CLAWDIA is intended as a community-driven, interoperable library extensible to additional tasks, including detection and parameter estimation.
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Instrumentation and Methods for Astrophysics
Validation of optical pathlength stability in a LISA test-bench demonstrator
Shivani Harer, Maxime Vincent, Hubert Halloin et al. (+40 more)
The
Laser Interferometer Space
Antenna (LISA) observatory is a future L3 mission of the European Space Agency (ESA) to detect gravitational waves, set to launch in 2035. The detector constellation will conduct interferometry to picometer stability over an unprecedented arm length of 2.5 million km. In this paper, we present the development and testing results for the Zerodur interferometer (ZIFO), an optical demonstrator built to validate critical technology for the test setup of the interferometric core of LISA. Optical path length stability measurements on the ZIFO demonstrate successful reduction of bench noise to maintain the 10 pm/$\sqrt{\text{Hz}}$ specification across the 1 mHz to 1 Hz frequency band. We also identify and characterize dominant noise sources from phasemeters and correlations of beam tilt into the path length that were observed during the test campaign.
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All authors Shivani Harer, Maxime Vincent, Hubert Halloin, Ouali Acef, Nisrine Arab, Romain Arguel, Axel Arhancet, Damien Bachet, Nathalie Besson, Sébastien Bize, Aurélien Boutin, Sara Bruhier, Christelle Buy, Michael Carle, Jean-Pierre Coulon, Nicoleta Dinu-Jaeger, Mathieu Dupont, Christophe Fabron, R'emi Granelli, David Holleville, Dominique Huet, Pascal Huguet Chantôme, Eric Kajfasz, Mickael Lacroix, Matthieu Laporte, Rodolphe Le Targat, Jean Lesrel, Michel Lintz, Michel Lours, Christophe Meessen, Mourad Merzougui, Alexis Mehlman, Marco Nardello, Laure Oudda, Benjamin Pointard, Pierre Prat, Emmanuelle Rivière, Jérôme Royon, Aurélia Secroun, Samuel Sube, Johannes Veyron, Thomas Zerguerras, Julien Zoubian
Cosmology and Nongalactic Astrophysics
A continuous parameterization of the cosmic web
C.Yamila Yaryura, Mario G. Abadi, Noam I. Libeskind et al. (+3 more)
The intrinsic properties of
galaxies are influenced by their environments, underscoring the environment's critical role in
galaxy formation and
evolution. Traditionally, these environments are categorized into four fixed classifications:
knots, filaments, walls, and voids, which collectively describe the complex organization of
galaxies within large-scale structures. We propose an alternative description that complements the traditional quadripartite categorization by introducing a continuous framework, allowing for a more nuanced examination of the relationship between the intrinsic properties of
galaxies and their environments. This complementary description is applied using one of the most prevalent methodologies: categorization using the
eigenvalues of the Hessian
matrix extracted from the matter density field. We integrated our findings into a semi-analytical model of
galaxy formation, combined with cosmological numerical simulations, to analyze how the intrinsic properties of
galaxies are influenced by environmental changes. In our study, we find a continuous distribution of
eigenvalue ratios, revealing a clear dependence of
galaxy properties on their surrounding environments. This method allowed us to identify critical values at which transitions in the behavior of key astrophysical
galaxy properties become evident.
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All authors C.Yamila Yaryura, Mario G. Abadi, Noam I. Libeskind, Stefan Gottlöber, Sofía A. Cora, Gustavo Yepes
Earth and Planetary Astrophysics
Zooming into the water snowline: high resolution water observations of the HL Tau disk
M. Leemker, S. Facchini, P. Curone et al. (+4 more)
Water is one of the central molecules for the formation and habitability of
planets. In particular, the region where water freezes-out, the water snowline, could be a favorable location to form
planets in protoplanetary disks. We use high resolution ALMA observations to spatially resolve H$_2$O, H$^{13}$CO$^+$ and SO emission in the HL Tau disk. A rotational diagram analysis is used to characterize the water reservoir seen with ALMA and compare this to the reservoir visible at mid- and far-IR wavelengths. We find that the H$_2$O 183 GHz line has a compact central component and a diffuse component that is seen out to ~75 au. A radially resolved rotational diagram shows that the excitation temperature of the water is ~350 K independent of radius. The steep drop in the water brightness temperature outside the central beam of the observations where the emission is optically thick is consistent with the water snowline being located inside the central beam ($\lesssim 6$ au) at the height probed by the observations. Comparing the ALMA lines to those seen at shorter wavelengths shows that only 0.02%-2% of the water reservoir is visible at mid- and far-IR wavelengths, respectively, due to optically thick
dust hiding the emission whereas 35-70% is visible with ALMA. An anti-correlation between the H$_2$O and H$^{13}$CO$^+$ emission is found but this is likely caused by optically thick
dust hiding the H$^{13}$CO$^+$ emission in the disk center. Finally, we see SO emission tracing the disk and for the first time in SO a molecular
outflow and the infalling streamer out to ~2". The velocity structure hints at a possible connection between the SO and the H$_2$O emission. Spatially resolved observations of H$_2$O lines at (sub-)mm wavelengths provide valuable constraints on the location of the water snowline, while probing the bulk of the gas-phase reservoirs.
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All authors M. Leemker, S. Facchini, P. Curone, L. Rampinelli, M. Benisty, A. Garufi, E. Humphreys
Solar and Stellar Astrophysics
The 12CO Gas Structures of Protoplanetary Disks in the Upper Scorpius Region
Luigi Zallio, Giovanni P. Rosotti, Miguel Vioque et al. (+13 more)
We present measurements of key protoplanetary disk properties inferred from parametric models of ALMA 12CO spectral line visibilities. We derive gas-disk radii, integrated fluxes, optically thick emission layers, and brightness temperature profiles for the disk population of the old (4 - 14 Myr) Upper Scorpius
star-forming region. We measure CO emission sizes for 37 disks with bright CO J=3-2 emission (S/N > 10 on the integrated flux; out of the 83 disks with CO detections), finding that the median radius containing 90% of the flux is ~84 au, with radii spanning from 23 up to 243 au. We report a correlation between the 12CO brightness temperatures and
stellar luminosities, with a Pearson coefficient of 0.6, and we use it to prove that the 12CO optically thick emission layer primarily emanates from a region below the super-heated
dust, which is optically thin to the
stellar irradiation. Moreover, we derive 33 CO emission surface height profiles, finding a median aspect ratio <z/r> ~ 0.16 in a range from ~0.01 up to ~0.45 over the sample. Finally, we comment on the multiple systems in our sample, of which only some were already known. These results re-affirm how it is possible to derive bulk disk properties by modeling moderate angular resolution ALMA visibilities.
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All authors Luigi Zallio, Giovanni P. Rosotti, Miguel Vioque, Anna Miotello, Sean M. Andrews, Carlo F. Manara, John M. Carpenter, Aaron Empey, Nicolás T. Kurtovic, Charles J. Law, Cristiano Longarini, Teresa Paneque-Carreño, Richard Teague, Marion Villenave, Hsi-Wei Yen, Francesco Zagaria
Astrophysics of Galaxies
Ivanna Langan, Gergö Popping, Michele Ginolfi et al. (+4 more)
The flow of
baryons in and out of
galaxies is the primary driver for
galaxy evolution. In addition to depleting the gas reservoir of
galaxies,
outflows also enrich their circumgalactic medium (CGM) with processed gas – which can further impact the next stages of gas
accretion, resulting in the presence of molecular gas beyond the
stellar component of
galaxies, out to CGM scales. Here, we aim to search for cold molecular gas (MH2) in the CGM of typical main-sequence (MS)
star-forming
galaxies (SFGs) at
cosmic noon (zmed=1.3), where we expect
outflows to be particularly prominent. Using Band 3 CO(2-1) data from the Atacama Large Millimeter and submillimeter Array (ALMA), we study the spatial extent of the MH2 of a sample of 26 SFGs, via stacking techniques. We compare this extent to that of the stacked
stellar emission of our sample traced by UltraVISTA Ks band data. We also search for broad wings in the stacked spectrum which can be indicative of ongoing
outflows. Within the noise level of the observations, we find that the total intrinsic MH2 of our sample spatially extends to scales of ~12 kpc, similarly to the
stellar emission (~13 kpc). We do not find broad wings in the stacked spectrum that could hint at ongoing molecular
outflows, but we find a tentative minor excess of CO(2-1) emission at negative velocities that might be indicative of
outflows, where the redshifted gas is optically thick. The absence of high-velocity molecular gas suggests that molecular
outflows traced by CO(2-1) emission are weak in MS SFGs at
cosmic noon. These weak
outflows thus fail to expel a significant amount of molecular gas to CGM scales, as indicated by the absence of molecular emission extending beyond the
stellar emission region. This lack of CO emission at large radii could also imply that the molecular gas does not survive at such distances.
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All authors Ivanna Langan, Gergö Popping, Michele Ginolfi, Simon Weng, Francesco Valentino, Gareth Jones, Jan Scholtz
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
WIMP Meets ALP: Coherent Freeze-Out of Dark Matter
Steven Ferrante, Maxim Perelstein and Bingrong Yu
We consider the cosmological history of a weakly interacting massive particle (WIMP) coupled to a light
axion-like particle (ALP) via a quadratic coupling. Although the coupling is too feeble to thermalize the ALP, coherent forward scattering between the two sectors induces temperature-dependent mass shifts that substantially modify both WIMP freeze-out and ALP misalignment dynamics, giving rise to a novel coherent freeze-out mechanism. At high temperatures, the WIMP thermal bath spontaneously breaks the
symmetry of the ALP potential, displacing the field to a new
vacuum. The resulting back-reaction reduces the WIMP effective mass and significantly delays its freeze-out. Depending on the strength of the coupling,
symmetry restoration occurs via either a first-order phase transition (FOPT) or a crossover. In the FOPT regime, dark matter consists solely of WIMPs, whose delayed freeze-out permits annihilation cross sections up to three orders of magnitude above the standard value, while still yielding the correct relic density. In the crossover regime, both WIMP and ALP can contribute to dark matter. Remarkably, we find an "ALP miracle": a Planck-suppressed quadratic coupling yields an ALP abundance comparable to the observed dark matter density, largely independent of its initial displacement and mass.
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Cosmology and Nongalactic Astrophysics
Evolution mapping III: A new recipe for the halo mass function
Andrea Fiorilli, Andrés N. Ruiz, Ariel G. Sanchez et al. (+1 more)
We present a new prescription for the
halo mass function (HMF) built upon the
Evolution Mapping framework. This approach provides a physical motivation to parametrise the non-universality of the HMF in terms of the recent history of structure formation and the local shape of the linear matter power spectrum. Our model was calibrated against measurements from N-body simulations, with
halo samples defined by ten overdensity thresholds, $\Delta$, ranging from 150 to 1600 times the mean background matter density. For our reference mass definition, $\Delta=200$, the calibrated fitting function achieves per cent-level accuracy across a wide range of masses,
redshifts, and structure formation histories, and maintains this performance when tested on cosmologies with different linear power spectrum shapes. This high level of accuracy is maintained across other mass definitions, degrading only slightly to the 5 per cent level at the highest values of $\Delta$. We also provide fitting formulae to interpolate the parameters as a function of $\Delta$, which allows for accurate modelling of HMFs defined by intermediate overdensities, with accuracy still well within 5 per cent when tested on
halo catalogues defined by the virial overdensity threshold. Compared to other commonly used recipes, our prescription yields competitive or superior accuracy across all
redshifts and cosmologies, successfully capturing the non-universal features of the HMF where other models exhibit systematic deviations. This work provides a high-precision modelling tool for cluster abundance analyses, and demonstrates the power of the
evolution mapping framework for building accurate models of observables in the non-linear regime.
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All authors Andrea Fiorilli, Andrés N. Ruiz, Ariel G. Sanchez, Matteo Esposito
Astrophysics of Galaxies
Radio-Continuum Spectra of Pulsars with Free-Free Thermal Absorption
Mario G. Abadi, Gabriela Castelletti and Namir E. Kassim
The
radio continuum spectra of
pulsars (PSRs) exhibit a wide variety of shapes, that are interpreted as pure and broken power laws, power laws with turnovers or cut-offs, and logarithmic-
parabolic profiles. A notable fraction of these have well-defined power laws with $\nu^{-2.1}$ exponential turnovers, indicative of free-free thermal absorption along the line-of-site. We analyse a sample of 63 PSRs with such spectral shapes, compiled from four previously published studies, to investigate their statistical properties. We normalise each spectrum to a characteristic frequency and flux density of its own, facilitating a consistent treatment across the four sub-samples. We show these two fitted parameters are correlated by a power law, with its slope reflecting the median spectral index ($\alpha\sim -2.0$) of PSR emission. We found that the turnover frequencies in our sample are typically high, clustering around 558 MHz, implying notably high emission measures ($EM \sim 10^{5}$ pc cm$^{-6}$) for an inferred thermal absorbing medium with electron temperature of $T_{\mathrm{e}}=8000$ K. Moreover, by combining these $EM$ with dispersion measures (DM) derived from pulse time delays, we break the degeneracy between electron density and path length of the absorbers. This reveals a discrete near-in population of absorbers characterised by small sizes ($L \sim 0.1\,\text{pc}$) and high electron densities $(n_{\mathrm{e}} \sim 10^{3}\,\text{cm}^{-3} $)), which exhibit a clear size-density anticorrelation reminiscent of that observed in
Galactic and extragalactic H$_\rm{II}$ regions.
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Astrophysics of Galaxies
HIDES – I. The population and diversity of HI-rich 'dark' galaxies in the Hestia and Auriga simulations
Haonan Zheng, Fangzhou Jiang, Shihong Liao et al. (+1 more)
We present our investigation of HI-rich 'Dark'
galaxiEs in Simulations (HIDES), specifically using the Hestia and Auriga simulations in this work. We select
galaxies that are faint ($M_g > -10$) and contain sufficient HI ($M_\mathrm{HI} > 10^5\,M_\odot$), and identify 89 such objects, only one of which is completely starless. Their demographics generally converge across simulations of different resolution, with $M_{200} \sim 10^{9.5}\,M_\odot$, $M_\mathrm{gas} \sim 10^{7.4}\,M_\odot$, $M_\mathrm{HI} \sim 10^{6.5}\,M_\odot$, $M_\mathrm{*} \sim 10^{5.6}\,M_\odot$, low gas
metallicity, little or no current
star formation, and a mean
stellar age of $\sim$ 11 Gyr, and with some of them can survive in dense environments as close as $\sim$ 300 kpc from a Milky-Way mass neighbor. We find a large scatter in their HI density profiles and $M_\mathrm{HI} - M_\mathrm{*}$ relation, which cannot be fully explained by current
halo mass or concentration, but can be attributed to ram pressure stripping in dense environments, past mergers, and
stellar feedback. In particular, close encounters with massive
halos and dense environments can reshape the HI content, which may explain the asymmetric HI map of an intriguing observed analogue, Cloud-9. An empirical fit, $n = 0.25 \left(d_\mathrm{MW}/{1\,\mathrm{Mpc}}\right)^{-1.4}\, \mathrm{Mpc}^{-3}$, based on their number density extended to 3.7 Mpc in constrained local volume simulations, is also provided to aid observational forecasts. We conclude that both mass assembly history and environmental history play a crucial role in the formation and subsequent diversity of these
galaxies.
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All authors Haonan Zheng, Fangzhou Jiang, Shihong Liao, Noam I. Libeskind
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Growth of Cosmic Strings with Field-Dependent Tension
Luca Brunelli
A novel mechanism to produce a
cosmic network of fundamental superstrings based on a time-varying string tension has been recently proposed. It has been found that fundamental superstrings can grow in a kinating background driven by the rolling of the volume modulus of Type IIB string compactifications towards the minimum of its potential. In this talk, I will generalise this analysis using dynamical systems techniques. First, I will analyse the cosmological growth of strings with a field-dependent tension in a Universe filled with a perfect fluid, finding a growth region in the phase space of this system. This machinery is then applied to both fundamental superstrings and effective strings obtained from wrapping $p$-branes on $(p-1)$- dimensional cycles. I will show how cosmological growth can be achieved in both cases not only in kinating backgrounds, but also in scaling fixed points. This talk is based on arXiv:2502.14953.
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Earth and Planetary Astrophysics
The Surface and Interior Conditions of Temperate Sub-Neptune TOI-270 d
Frances E. Rigby and Nikku Madhusudhan
Sub-Neptune
planets, with no analogue in our
solar system, provide a wealth of information about
exoplanet diversity, formation &
evolution, and habitability. Their robust characterisation requires the coupling of physically informed atmosphere and interior models with precise atmospheric data to break compositional degeneracies. Recent JWST observations of the temperate sub-Neptune TOI-270 d revealed detections of CH$_4$ and CO$_2$ in its H$_2$-rich atmosphere, with tentative inferences of H$_2$O and CS$_2$ and a non-detection of NH$_3$. We conduct a theoretical exploration of the range of possible interiors for TOI-270 d based on the current observational constraints. We carry out internal structure modelling using a coupled atmosphere-interior model, including self-consistent atmospheric temperature structures informed by JWST observations. The bulk properties permit solutions spanning mini-Neptune, gas
dwarf and hycean scenarios, with a wide range of possible surface conditions, which are strongly dependent on the atmospheric properties, including the presence of clouds/hazes. We explore the solutions allowing for surface water oceans on TOI-270 d, including under potentially habitable conditions. The atmospheric mass fractions permitting habitable surface conditions are found to be $\lesssim$$3.5\times10^{-5}$ and pressures $\lesssim$100 bar for the envelope temperature structures considered. We consider mini-Neptune interiors that are sufficiently warm for H$_2$O to be mixed with the H$_2$-rich envelope. Finally, we consider possible gas
dwarf interiors, finding H$_2$-rich envelope mass fractions of $\sim$$1-5$ % are required to satisfy the bulk properties, with surface pressures $\sim10^4-10^5$ bar. Further theoretical and experimental studies in addition to future atmospheric observations will aid the characterisation of the possible interior and surface conditions on TOI-270 d.
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Astrophysics of Galaxies
The CO-to-H$_2$ conversion factor in the Milky Way's central parsec
Mark Gorski and Lena Murchikova
Carbon monoxide (CO) emission is a widely used tracer of molecular hydrogen (H$_2$) in the interstellar medium (ISM), owing to its abundance, low excitation energy, and ease of detection in cold molecular environments, in contrast to $\mathrm{H}_2$ itself. While the CO-to-$\mathrm{H}_2$ conversion factor is often assumed to be constant across the disks of
galaxies, deviations are observed in extreme environments such as the central molecular zone (CMZ) in
galactic nuclei. Here we present the first estimate of the CO-to-$\mathrm{H}_2$ conversion factor on sub-kpc scales. We calculate CO-to-$\mathrm{H}_2$ conversion in the Milky Way's Circumnuclear Disk/Ring (CND/CNR) at $\sim 1$ pc radius around the
Galactic Center black hole. We derive a conversion factor of $\alpha_\mathrm{CO} \simeq 4.5\pm2.5 \, M_\odot (\mathrm{K \, km \, s^{-1} pc^2})^{-1}$ or X[CO] $\simeq (2.1\pm1.1)\times 10^{20} \, \mathrm{cm}^{-2} (\mathrm{K \, km \, s^{-1}})^{-1}$. This value is consistent with the
Galactic disk but higher than CMZ.
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Instrumentation and Methods for Astrophysics
Habitable from the start: How initial planetary formation conditions may create habitable worlds
Benjamin J. Farcy, Darryl Z. Seligman, Kathleen E. Mandt et al. (+2 more)
The breadth of topics that encompass the search for life has expanded and evolved significantly since the emergence of the field of astrobiology. Initial astrobiology centered investigations focused on detecting biosignatures in the Martian soil with the Viking lander. The field now encompasses identification of biosignatures throughout the
galaxy and habitable worlds,
planets with sufficient
liquid water and prebiotic chemistry to support life. This
evolution mirrors the improvement in our understanding of environments that may harbor life. The bulk planetary chemistry governs the habitability of a
planet, which is in turn set by the early
solar system environment and
planet formation processes. Therefore, investigations of
solar and exoplanetary systems as a whole would provide insights into the factors that make a
planet habitable. Bulk planetary chemistry govern planetary atmospheres, core sizes,
magnetic fields, heat engines, volatile inventories, and silicate mantle compositions. We therefore advocate for investigations of formation conditions that establish planetary chemistry, and by extension, habitability.
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All authors Benjamin J. Farcy, Darryl Z. Seligman, Kathleen E. Mandt, John W. Noonan, Sarah E. Anderson
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Prospects for Neutrino Observation and Mass Measurement from Binary Neutron Star Mergers
Vedran Brdar, Dibya S. Chattopadhyay, Samiur R. Mir et al. (+2 more)
Over the next decade, $\mathcal{O}(100)$ diffuse
supernova neutrino background (DSNB) events are expected in Hyper-Kamiokande. Another
neutrino source that has received far less
attention is binary
neutron star mergers. Including the data from recent simulations, we find that detection in current and near-future
neutrino experiments is not feasible, and a megaton-scale detector with $\mathcal{O}(10)$ MeV threshold, such as the proposed Deep-TITAND, MEMPHYS, or MICA, will be required. This is due to the updated binary
neutron star merger rate and the time-of-flight delay caused by the nonzero
neutrino mass. Regarding the former, recent results from LIGO, Virgo, and KAGRA has significantly lowered the upper limit on the
neutron star merger rate. As for the latter,
neutrino events from
neutron star mergers are expected to be recorded shortly after the gravitational wave signal. Limiting the analysis to such short time windows can significantly reduce background rates. While this approach has been qualitatively discussed in the literature, the effect of the time delay caused by
neutrino mass, which can substantially extend the observation windows, has been disregarded. We present a refined analysis employing energy-dependent time windows and luminosity distance cuts for the mergers and provide realistic estimates of the detector runtime required to record
neutrinos from binary
neutron star mergers with small background contamination. The relative timing between the
neutrino and gravitational wave signals can also be employed to probe the scale of
neutrino mass. We find that the sensitivity to the lightest
neutrino mass exceeds both the most stringent terrestrial bounds from KATRIN and the projections based on
galactic supernovae. This level of sensitivity may become particularly relevant in the future if terrestrial and
supernova constraints are not significantly improved.
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All authors Vedran Brdar, Dibya S. Chattopadhyay, Samiur R. Mir, Tousif Raza, Marc S. Romanowski
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Domain walls in the scaling regime: Equal Time Correlator and Gravitational Waves
Simone Blasi, Alberto Mariotti, Aäron Rase et al. (+1 more)
Domain walls are topological defects that may have formed in the early Universe through the spontaneous breakdown of discrete
symmetries, and can be a strong source of gravitational waves (GWs). We perform 3D
lattice field theory simulations with CosmoLattice, considering grid sizes $N = 1250$, $2048$ and $4096$, to study the dynamics of the domain wall network and its GW signatures. We first analyze how the network approaches the scaling regime with a constant $\mathcal{O}(1)$ number of domain walls per Hubble volume, including setups with a large initial number of domains as expected in realistic scenarios, and find that scaling is always reached in a few Hubble times after the network formation. To better understand the properties of the scaling regime, we then numerically extract the Equal Time Correlator (ETC) of the energy-momentum tensor of the network, thus determining its characteristic shape for the case of domain walls, and verifying explicitly its functional dependence as predicted by scaling arguments. The ETC can be further extended to the Unequal Time Correlator (UTC) controlling the GW emission by making assumptions on the coherence of the source. By comparison with the actual GW spectrum evaluated by CosmoLattice, we are then able to infer the degree of coherence of the domain wall network. Finally, by performing numerical simulations in different background cosmologies, e.g. radiation domination and kination, we find evidence for a universal ETC at subhorizon scales and hence a universal shape of the GW spectrum in the UV, while the expansion history of the Universe may instead be determined by the IR features of the GW spectrum.
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All authors Simone Blasi, Alberto Mariotti, Aäron Rase, Miguel Vanvlasselaer
High Energy Astrophysical Phenomena
Lucky Strikes: On the Origins of GW190814 Through Isolated Binary Evolution
Ignacio Magaña Hernandez and Katelyn Breivik
The asymmetric nature of GW190814, particularly its mass ratio ($q \approx 1/10$), has made its astrophysical origin elusive. We explore isolated binary
evolution as a potential explanation for GW190814's formation. Using the binary population synthesis code
COSMIC, and the backpop sampling technique to map the observed parameters of GW190814 to the initial conditions of Zero Age Main Sequence binary
stars while simultaneously inferring the astrophysical prescriptions for common envelope
evolution, stable mass transfer and natal kick kinematics that are needed for its formation and eventual merger. We find that the initial conditions for the binary
stellar population that forms GW190814 do not stand out significantly from massive
star populations observed in the Local Group. Our backpop simulations recover a dominant formation pathway where the first Roche overflow phase includes a common envelope
evolution and the second Roche overflow phase remains stable. Our findings suggest that natal kicks imparted during compact object formation play the strongest role in forming GW190814-like systems. Specifically, our models require a low magnitude first natal kick (independent of direction) that prevents the binary from unbinding and a large second natal kick with its direction in the plane of the orbit and toward the binary's center of mass. The second natal kick strength and direction crucially increases the orbital eccentricity, leading to shorter delay times, and thus enabling mergers within a Hubble time. We estimate the chance probability for GW190814-like events that experience such a lucky kick and find that it occurs in $\sim20\%$ of systems if natal kicks are randomly oriented. We discuss the astrophysical implications for the formation of asymmetric GW190814-like systems under the context of binary
stellar evolution.
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High Energy Astrophysical Phenomena
A Core-Collapse Supernova Neutrino Parameterization with Enhanced Physical Interpretability
Haihao Shi, Zhenyang Huang, Junda Zhou et al. (+2 more)
We introduce a novel parameterization of
supernova neutrino energy spectra with a clear physical motivation. Its central parameter, $\tau(t)$, quantifies the characteristic thermal-
diffusion area during the explosion. When applied to the historic SN1987A data, this parameterization yields statistically significant fits and provides robust constraints on the unobserved low-energy portion of the spectrum. Beyond this specific application, we demonstrate the model's power on a suite of 3D core-collapse
supernova simulations, finding that the temporal
evolution of $\tau(t)$ distinctly separates successful from failed explosions. Furthermore, we constrain the progenitor mass of SN 1987A to approximately 19
solar masses by applying Smoothed Isotonic Regression, while noting the sensitivity of this estimate to observational uncertainties. Moreover, in these simulations, $\tau(t)$ and the gravitational-wave strain amplitude display a strong, synergistic co-
evolution, directly linking the engine's energetic
evolution to its
geometric asymmetry. This implies that the thermodynamic state of the explosion is imprinted not only on the escaping
neutrino flux, but also recorded in the shape of the energy spectrum. Our framework therefore offers a valuable tool for decoding the detailed core dynamics and multi-messenger processes of future
galactic supernovae.
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All authors Haihao Shi, Zhenyang Huang, Junda Zhou, Guoliang Lü, Xuefei Chen
Solar and Stellar Astrophysics
Excitation of Inertial Modes in 3D Simulations of Rotating Convection in Planets and Stars
J. R. Fuentes, Ankit Barik and Jim Fuller
Thermal convection in rotating
stars and
planets drives anisotropic
turbulence and differential rotation, both capable of feeding energy into global oscillations. Using 3D simulations of rotating convection in spherical shells, we show that inertial modes–oscillations restored by the Coriolis force–emerge naturally in rotationally constrained
turbulence, without imposing any external forcing other than thermal/buoyancy driving. By varying the rotation rate at fixed Rayleigh number, we find that coherent modes appear only when the convective Rossby number, the ratio of the rotation period to the convective turnover time, falls below about one-half, where rotation dominates the dynamics. These modes are mostly retrograde in the rotating frame, equatorially symmetric, and confined to mid and high latitudes, with discrete frequencies well below twice the background rotation rate. At lower viscosities, or smaller Prandtl number, mode excitation becomes more efficient and a broader spectrum of inertial modes emerges. While the precise excitation mechanism remains uncertain, our results suggest that the modes are driven by instabilities due to differential rotation rather than
stochastic forcing by convection. We conclude that similar inertial modes are likely to exist in the interiors of
giant planets and
stars, though their low frequencies will make them difficult to detect.
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