Astrophysics of Galaxies
It's a matter of time: Empirical Constraints on Supernova Yields and Delay Times from Dwarf Spheroidal Galaxies
Mairéad E. Heiger, Alexander P. Ji, Joshua S. Speagle et al. (+6 more)
The chemical abundances of a
stellar population encode information about nucleosynthesis and its astrophysical sites, but this information is confounded by the specific
star formation history of the host
galaxy. As a result, placing empirical constraints on
supernova yields and timing using abundances has been very challenging. We introduce a
galactic chemical
evolution model DLEIY that uses an observed
star formation history and
metallicity distribution to reduce these confounding factors. Using a joint statistical model of the
dwarf spheroidal
galaxies Sculptor and Fornax, simultaneous constraints on population-averaged yields and
galactic outflows are achieved with DLEIY, without fixing the absolute scale of nucleosynthetic yields. The Fe yield from core collapse
supernovae is consistent with existing theoretical yield models, while the measured Mg yield is a factor of 2-4 higher, corroborating previous suggestions that yield models may under-predict [Mg/Fe]. We also find that the rate of Type Ia
supernovae is enhanced by about a factor of 5 relative to field
galaxies, and the delay-time distribution goes as $\sim t^{-2}$, a much steeper relationship than that measured from
supernova surveys ($\sim t^{-1.1}$). These findings may suggest a
metallicity dependence of the Type Ia rate and delay-time distribution.
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All authors Mairéad E. Heiger, Alexander P. Ji, Joshua S. Speagle, Ting S. Li, Alessandro Savino, Nathan R. Sandford, Evan N. Kirby, Mithi A. C. de los Reyes, Joshua D. Simon
Earth and Planetary Astrophysics
JWST COMPASS: A NIRSpec G395H Transmission Spectrum of Radius Valley-Dweller TOI-260 b
Annabella Meech, Peter Gao, Nicole L. Wallack et al. (+16 more)
We present a JWST/NIRSpec G395H transmission spectrum of TOI-260 b, a $T_\mathrm{eq}\sim 490$ K, $R_\mathrm{p} = 1.76\,R_\oplus$
planet. The transmission spectrum is derived by combining two transit observations, collected as part of the JWST COMPASS program. We achieved the same median transit depth precision of 37 ppm in both visits, and a median precision of 26 ppm when combining the spectroscopic light curves from the two visits. Implementing a 30-pixel-wide ($R\sim 200$) spectroscopic binning scheme, we find that the transmission spectrum is mostly featureless, with a possible feature around 3.17 $\mu$m. We assess the significance of any features in the transmission spectrum with a suite of non-parametric models, which confirm the presence of a potential feature in the NRS1 bandpass and an offset between the NRS1 and NRS2 detectors. To investigate the atmospheric composition of TOI-260 b, we run a series of PLATON
retrievals. We do not detect any clear molecular signatures, but the combined data from the two visits are sufficient to constrain the atmospheric
metallicity to greater than $200\times$
solar, assuming no opaque deck $\lesssim2.5$ mbar. We also investigate causes of the potential feature near 3.17 $\mu$m; while we find some compatible gaseous species and cannot fully discard an astrophysical origin, we suspect a systematics origin due to the variance in strength and position of the feature. Overall, this look at TOI-260 b adds to the small sample of radius-valley
planets, which already seem to show a diversity in their atmospheric compositions. Determining the true nature of these enigmatic
planets will require a larger
telescope time investment.
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All authors Annabella Meech, Peter Gao, Nicole L. Wallack, Mercedes López-Morales, Dominic Oddo, Johanna Teske, Diana Dragomir, Angie Wolfgang, Nicholas Wogan, Hannah R. Wakeford, Sarah E. Moran, James Kirk, Tyler A. Gordon, Anna Gagnebin, Natasha E. Batalha, Natalie M. Batalha, Lili Alderson, Munazza K. Alam, Artyom Aguichine
Earth and Planetary Astrophysics
JWST COMPASS: NIRSpec/G395H Transmission Observations of the Sub-Neptune HD 15337 c
Nicole L. Wallack, Peter Gao, Michael Greklek-McKeon et al. (+17 more)
We present the 3-5 $\mu$m transmission spectrum of HD 15337 c (TOI-402.02), a sub-Neptune (2.526 R$_{\oplus}$, 6.792 M$_{\oplus}$, T$_{\rm eq}$$\sim$656 K) around a K1V
star observed as part of the JWST COMPASS program. We reduce these observations with two pipelines and find consistent transmission spectra. The resulting median precisions in 30 pixel spectroscopic bins for visit 1 are $\sim$40 ppm and $\sim$70 ppm and for visit 2 are $\sim$30 ppm and $\sim$54 ppm for NRS1 and NRS2, respectively. We attribute the differing precisions to the lack of adequate pre-transit baseline in visit 1 from an early transit arrival caused by previously undetected transit timing variations (TTVs), hinting at a potential exterior companion. Our median JWST timing precision is 10 seconds, revealing TTVs $>$20 minutes when combined with previous TESS and CHEOPS data, highlighting JWST's TTV measurement capabilities. The transmission spectrum of HD 15337 c is featureless and can best be described by a step function with an offset between the NRS1 and NRS2 detectors, likely caused by instrumental systematics. From thermochemical
equilibrium retrievals we find that, to $>$3$\sigma$, the data can rule out atmospheres with
metallicities $<$600 or $<$310 $\times$
solar, depending on the reduction, for opaque pressures greater than a few millibars. HD 15337 c joins other sub-Neptunes with similar masses, radii, and temperatures in possessing a featureless transmission spectrum indicative of high
metallicity and/or high-altitude aerosols and adds support to recent studies showing that aerosol opacity reaches a maximum for
planets with
equilibrium temperatures of 500-700 K.
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All authors Nicole L. Wallack, Peter Gao, Michael Greklek-McKeon, Annabella Meech, Artyom Aguichine, Munazza K. Alam, Lili Alderson, Natasha E. Batalha, Natalie M. Batalha, Anna Gagnebin, Tyler A. Gordon, James Kirk, Mercedes López-Morales, Sarah E. Moran, Jea Iyanla Redai, Nicholas Scarsdale, Johanna Teske, Hannah R. Wakeford, Nicholas F. Wogan, Angie Wolfgang
Astrophysics of Galaxies
Filamentary Hierarchies and Superbubbles II: Impact of superbubbles and galactic dynamics on filament formation and fragmentation
Rachel Pillsworth, Ralph E. Pudritz, Eric W. Koch et al. (+1 more)
Large scale phenomena in spiral
galaxies such as shear,
supernovae, and
magnetic fields all contribute to the formation and subsequent
evolution of filamentary structure and
star formation within them. In this paper, we analyze the properties and dynamics of filaments in a simulated Milky Way-like
galaxy from Zhao et al. 2024. Using filament and superbubble structure analysis codes, we investigate the roles of
galactic shear,
supernovae and superbubbles, and
magnetic fields on the stability and fragmentation of filaments. We find that local shear has little effect on filament stability and the largest structures at outer radii of the disk may be more likely to be dissipated by shear than
supernovae. Filaments are largely parallel to the
magnetic field, which plays a significant role in filament stability. By measuring the ratio of surface pressure on a filament to that on its central spine, $\chi_f=P_{surf}/P_{central}$, we find that filaments with $\chi_f \le 1$ are dominated by their own self
gravity and have a strong tendency to be gravitationally supercritical, whereas those with $\chi_f > 1$ are either transitory or in the act of being formed. Finally, we investigate the role of ISM pressure on filament dynamics and stability as a function of
galactic radius, finding considerable changes in filament stability and the accompanying
star formation rates in the inner versus outer regions of the disk.
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All authors Rachel Pillsworth, Ralph E. Pudritz, Eric W. Koch, Theo J. O'Neill
High Energy Astrophysical Phenomena
XRISM Observation of the Supernova Remnant N103B: Velocity Structure and Thermal Properties
Tyler Holland-Ashford and Brian J. Williams
We present the first analysis of the X-ray Imaging and Spectroscopy Mission (XRISM) observation of the
supernova remnant (SNR) N103B. We fit the X-ray spectrum taken with the Resolve microcalorimeter, which captured emission lines from the predominantly ejecta elements Si, S, Ar, Ca, Cr, Mn, and Fe. Notably, our fits require a previously unidentified high-temperature, highly-ionized, Fe-dominated
plasma component with particularly high Cr and Mn abundances, matching a feature also present in the recent XRISM analysis of the SNR N132D. We find that all ejecta in N103B exhibits significant line broadening arising mostly from thermal Doppler broadening: increasing from $\sigma_{\rm th}\sim1700$ km s$^{-1}$ for intermediate-mass element (IME: Si, S, Ar, and Ca) ejecta to $\sim$2800 km s$^{-1}$ for Fe-rich ejecta. These velocities correspond to reverse shock velocities of $\sim$3500 and $\sim$5900 km s$^{-1}$, respectively, in the ejecta frame of rest. Finally, we find that the IMEs are redshifted with a bulk velocity of $\sim$360 km s$^{-1}$ while the Fe-dominated components are split: one redshifted at $\sim$1560 km s$^{-1}$ and the other blueshifted at $\sim$1020 km s$^{-1}$. Our results provide further support for the double-ring structure of N103B as it expands into the bipolar winds of a non-degenerate companion and highlight the strength of high-resolution spectroscopic observations of SNRs.
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High Energy Astrophysical Phenomena
A steadily declining dispersion measure for the repeating fast radio burst FRB 20220529A: Evidence for an FRB engine embedded in an expanding supernova remnant
Ayush Pandhi, Kenzie Nimmo, Shion Andrew et al. (+29 more)
We present the discovery and subsequent 3.2 year monitoring campaign of the repeating fast
radio burst FRB 20220529A with CHIME/FRB. We observe a gradual dispersion measure (DM) decline of $-0.881\pm0.001~\mathrm{pc}~\mathrm{cm}^{-3}~\mathrm{year}^{-1}$ ($-1.235\pm0.001~\mathrm{pc}~\mathrm{cm}^{-3}~\mathrm{year}^{-1}$ in the rest frame), implying a $\geq3.5\pm0.2$% decrease of the total electron column in the source environment, and we see scattering timescale variations over weeks to years. We observe a short-lived excursion in which the DM rises by $\sim 1~\mathrm{pc}~\mathrm{cm}^{-3}$, immediately preceding a transient $\sim 2000~\mathrm{rad}~\mathrm{m}^{-2}$ Faraday rotation measure (RM) increase previously reported for this source, before returning to its gradual DM decline. We identify a local line-of-sight
magnetic field around FRB 20220529A during this DM/RM excursion of $3.4 \pm 0.2~\mathrm{mG}$, corresponding to one of the most strongly magnetized FRB environments. We measure a decrease in the linear polarization fraction of FRB 20220529A bursts with decreasing frequency that we attribute to depolarization from multi-path propagation in the source environment. We also place a $5\sigma$ upper limit on the spectral luminosity of an associated persistent
radio source of $\leq 5\times10^{28}~\mathrm{erg}~\mathrm{s}^{-1}~\mathrm{Hz}^{-1}$ at 1.5 GHz. These observations are consistent with FRB 20220529A originating from a young ($\sim$ years to centuries old) expanding
supernova remnant, with short-lived DM and RM variability arising from interactions with the
supernova remnant or with a binary companion.
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All authors Ayush Pandhi, Kenzie Nimmo, Shion Andrew, Charanjot Brar, Shami Chatterjee, Amanda M. Cook, Alice Curtin, B. M. Gaensler, Marcin Gawroński, Jason Hessels, Victoria M. Kaspi, Afrokk Khan, Franz Kirsten, Mattias Lazda, Calvin Leung, Robert Main, Kiyoshi W. Masui, Ryan Mckinven, Daniele Michilli, Mason Ng, Omar Ould-Boukattine, Aaron B. Pearlman, Ziggy Pleunis, Alexander W. Pollak, Sachin Pradeep E. T., Weronika Puchalska, Mawson W. Sammons, Paul Scholz, Vishwangi Shah, Kaitlyn Shin, Seth R. Siegel, Kendrick Smith
Cosmology and Nongalactic Astrophysics · Cross-listed from stat.ME
Global structure of the time delay likelihood
Namu Kroupa and Will Handley
We identify a fundamental pathology in the likelihood for time delay inference which challenges standard inference methods. By analysing the likelihood for time delay inference with Gaussian process light curve models, we show that it generically develops a boundary-driven "W"-shape with a global maximum at the true delay and gradual rises towards the edges of the observation window. This arises because time delay estimation is intrinsically extrapolative. In practice, global samplers such as nested sampling are steered towards spurious edge modes unless strict convergence criteria are adopted. We demonstrate this with simulations and show that the effect strengthens with higher data density over a fixed time span. To ensure convergence, we provide concrete guidance, notably increasing the number of live points. Further, we show that methods implicitly favouring small delays, for example optimisers and local MCMC, induce a bias towards larger $H_0$. Our results clarify failure modes and offer practical remedies for robust fully
Bayesian time delay inference.
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Astrophysics of Galaxies
A Morphology Catalog of Galaxies in CEERS: Evolution in the Size and Color Gradients of Galaxies Since Cosmic Dawn
Elizabeth J. McGrath, Steven L. Finkelstein, Guillermo Barro et al. (+42 more)
We present measurements of morphological parameters from fitting 53,885
galaxies detected to a magnitude limit of F356W$< 28.5$ in the CEERS NIRCam imaging with galfit in six broadband filters: F115W, F150W, F200W, F277W, F356W, and F444W. We provide a public catalog of Sérsic index, effective semi-major axis, axis ratio, integrated magnitude, and position angle for these
galaxies in each of the filters. Uncertainties in the measured parameters are estimated from simulated
galaxies that have similar noise and background properties as the observed
galaxies. We compare our measurements with those in the CANDELS/EGS field measured with HST/WFC3 and find that the sizes agree to within 0.09 dex and the Sérsic indices agree to within 0.13 dex. We further present the
evolution in the size-mass relation, and find that the
evolution to $z\sim9$ is consistent with previous results derived at lower
redshift. Finally, we look at the color gradients of
galaxies at $1<z<5$ and find that for late-type
galaxies ($n<2.5$), there is a strong dependence on mass, but no apparent
evolution with
redshift, indicating that the
stellar populations and
dust attenuation in more massive
galaxies vary substantially with radius and contribute to significant morphological $k-$corrections. For early type
galaxies ($n>2.5$), the color gradients are nearly flat with no dependence on mass, indicating that the
stellar populations are more uniform throughout. The structural measurements presented are accurate to $20\%$ or better for most
galaxies with F356W $<27.0$ mag and will enable further studies of
galaxy morphology to $z\sim10$.
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All authors Elizabeth J. McGrath, Steven L. Finkelstein, Guillermo Barro, Viraj Pandya, Jeyhan S. Kartaltepe, Dale D. Kocevski, Ricardo O. Amorín, Bren E. Backhaus, Fernando Buitrago, Antonello Calabrò, Yingjie Cheng, Luca Costantin, Isa G. Cox, Kelcey Davis, Giovanni Gandolfi, Yuchen Guo, Nimish P. Hathi, Michaela Hirschmann, Benne W. Holwerda, Marc Huertas-Company, Anton M. Koekemoer, Ray A. Lucas, Bahram Mobasher, Fabio Pacucci, Casey Papovich, Pablo G. Pérez-González, Jonathan R. Trump, L. Y. Aaron Yung, Pablo Arrabal Haro, Micaela B. Bagley, Mark Dickinson, Adriano Fontana, Andrea Grazian, Norman A. Grogin, Lisa J. Kewley, Allison Kirkpatrick, Jennifer M. Lotz, Laura Pentericci, Nor Pirzkal, Swara Ravindranath, Rachel S. Somerville, Stephen M. Wilkins, Guang Yang, Lise-Marie Seillé, Xin Wang
Astrophysics of Galaxies
You can't see me: Super-Eddington growth hindering X-ray detection in high-z broad-line active galactic nuclei
Alessandro Trinca, Alessandro Lupi, Francesco Haardt et al. (+1 more)
We revisit black hole mass estimates for high-
redshift broad-line active
galactic nuclei (AGNs) discovered with JWST by jointly analysing their broad emission lines and their systematic non-detections in deep Chandra imaging. Building upon a self-shadowed, super-Eddington
accretion framework in which the corona undergoes efficient radiative over-cooling, we couple funnel-dependent Comptonisation physics with slim-disc spectral models and explore the resulting parameter space through a full MCMC inference. Using a recently compiled sample of JWST high-
redshift broad-line AGNs, we show that the observed X-ray weakness - manifested as extreme bolometric corrections, suppressed 2-10 keV luminosities, and non-detections in the 0.5-5 keV Chandra band - naturally arises when the corona is confined and radiatively over-cooled inside a narrow super-Eddington funnel. The combined broad line+X-ray analysis yields strongly bimodal posteriors: either very massive, very low-Eddington black holes (physically disfavoured), or a population of low-mass ($\sim 10^{6}$-$10^{7} M_{\odot}$) black holes accreting at $f_{\rm Edd} \gg 1$. The latter solution is strongly preferred for nearly all objects and returns masses consistent with, or lower than, local $M_{\rm BH}$-$M_{\star}$ relations, mitigating the extreme mass ratios implied by single-epoch virial
estimators. The predicted intrinsic spectra are redder and exhibit reduced hard-X-ray output but higher bolometric luminosities, implying bolometric corrections larger than those typical of the local AGN population, yet consistent with low-
redshift highly accreting counterparts. These results support a picture in which many JWST broad-line AGNs are powered by rapidly growing, super-Eddington black holes whose suppressed coronal emission and self-shadowed BLR geometry combine to mimic overmassive black holes at $z \gtrsim 6$.
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All authors Alessandro Trinca, Alessandro Lupi, Francesco Haardt, Piero Madau
Astrophysics of Galaxies
Gaia DR3 Analysis of Four Open Clusters Toward the Galactic Anticenter
Selçuk Bilir, Seval Taşdemir, Ege Erayd{\i}n et al. (+3 more)
This study provides a detailed examination of the structural, astrophysical, kinematic, and dynamical properties of the open clusters COIN-
Gaia 24, Czernik 24, FSR 0893, and UBC 74, which are located in the direction opposite to the
Galactic center. Astrometric, photometric, and spectroscopic data from the
Gaia Data Release 3 catalog were used to ensure a precise characterization of cluster members and their physical properties. Membership determination was performed using the UPMASK
algorithm applied to a five-dimensional parameter space, yielding 116, 179, 238, and 387 likely members for each cluster, respectively. Structural parameters were derived by fitting King profiles to the radial density distributions of high-probability members. Astrophysical parameters were estimated through
Bayesian Markov Chain Monte Carlo isochrone fitting based on PARSEC evolutionary models, complemented by spectral energy distribution analysis using ARIADNE. The resulting extinctions, distances,
metallicities, and ages indicate that these are moderately reddened, intermediate-age clusters located between 1 and 3.5 kpc from the Sun. Mean radial velocities combined with
Galactic orbital integrations computed with galpy show that all four clusters follow nearly circular, low-eccentricity orbits typical of thin-disc populations. All four OCs have dynamical relaxation times of 22-98 Myr. However, their ages exceed these times by several factors, particularly in Czernik 24, indicating that they are dynamically evolved systems, even though the calculated T_E values represent lower limits. The results confirm that these OCs serve as reliable tracers of the chemical and dynamical
evolution of the
Galactic thin disc.
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All authors Selçuk Bilir, Seval Taşdemir, Ege Erayd{\i}n, Deniz Cennet Ç{\i}nar, Jeison Alfonso, Remziye Canbay
Solar and Stellar Astrophysics · Cross-listed from physics.space-ph
Fluctuating polytropic processes, turbulence, and heating
G. Livadiotis and D.J. McComas
This paper explores the thermodynamics of fluctuating polytropic processes and their connection to
turbulence. It is shown that random fluctuations of polytropic processes produce a nonzero overall heating of a particle system, e.g.,
solar wind
plasma flowing out through the heliosphere; while any nonturbulent heating can be thermodynamically described by typical nonfluctuating polytropic processes, turbulent heating can be thermodynamically described through fluctuating polytropic processes. First, we derive the expression of the overall process and find that polytropic fluctuations lead to heat entering the system even if the respective nonfluctuating process is adiabatic. The temperature of the
solar wind
plasma protons decreases with heliospheric distance less than the adiabatic cooling, again, similar to when heating enters the system; this subadiabatic cooling is proportional to the variance of the fluctuations. We derive the heliospheric radial profiles of the thermodynamic expressions of the polytropic index, temperature, and heating rates. Then, we show that the analytical profiles of heating of fluctuating polytropic processes and of turbulent heating are identical, suggesting that
turbulence heats
plasma particle populations by fluctuating their polytropic processes. We apply the thermodynamics of fluctuating polytropic processes to the energy transfer from pickup ions (PUIs) to
solar wind
plasma protons, and derive the analytical expressions of PUI turbulent and nonturbulent heating rates, which are well fitted to the respective observations. Finally, we apply the thermodynamic model to the radial profile of PUI energy transfer to the
solar wind
plasma protons, where we derive the portion of PUI turbulent vs. nonturbulent heating rates.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Conformal symmetry in force-free electrodynamics
Huiquan Li and Jianyong Wang
It is shown that conformal
symmetry exists in force-free electrodynamics (FFE) in Minkowski spacetime, a foundational framework for describing magnetospheres around astronomical objects. In force-free magnetospheres, charges are constrained to move along
magnetic field lines and experience zero Lorentz force, due to the everywhere perpendicular orientation of electric and
magnetic fields. However, a general angle-preserving conformal mapping of force-free fields does not necessarily produce another physically admissible force-free configuration when sources are present. In this work, we demonstrate that such invariance can nevertheless arise for certain choices of the free functions. Specifically, the governing stream equation is shown to be invariant under Möbius transformations. This
symmetry reveals a structural linkage between known solutions and, notably, maps the region inside a magnetospheric horizon (the lightsurface) of one solution to the exterior of its dual counterpart, and vice versa.
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Astrophysics of Galaxies
SIRIUS: The relation between the diversity of dwarf galaxies and their formation histories
Chi-Hong Lin, Michiko S Fujii, Takayuki R Saitoh et al. (+1 more)
Low-mass
dwarf galaxies ($M_{\rm vir} \lesssim 10^9\rm\ M_\odot$) are fundamental cosmological building blocks, yet the physical processes driving their structural diversity remain poorly understood. Recent numerical simulations have suggested a diversity in the
stellar-to-
halo mass ratio in this
halo mass range, but either the number of samples obtained from the same simulation setup or the numerical resolution was limited. We performed high-resolution cosmological zoom-in simulations for eight
galaxies with a dark matter
halo mass of $\sim 10^9\rm\ M_{\odot}$ up to $t=1.2$ Gyr at which most gas in the
galaxies has been expelled. Our samples have a scatter of an order of magnitude in the
halo mass at the reionization epoch. The
stellar-to-
halo mass ratio expected at $z=0$ scatters nearly two orders of magnitude with $5\times10^{-5}$ to $2\times10^{-3}$. We also observed variation in the compactness of their
stellar distributions. Some of our simulated
galaxies exhibit a
stellar half-mass radius of $\sim30$ pc, which is as small as that of ultra-compact
dwarfs. The formation condition for such a compact
stellar distribution is understood as an analog of the condition for the formation of dense, massive
star clusters. We found that when the central gas surface density exceeds a critical threshold ($\Sigma_{\rm gas} \gtrsim 30\rm\ M_\odot \rm\ {pc}^{-2}$), the
star formation becomes highly efficient and results in dense
stellar systems. These results suggest that UCDs can form in situ even in isolated dark matter
halos.
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All authors Chi-Hong Lin, Michiko S Fujii, Takayuki R Saitoh, Yutaka Hirai
Astrophysics of Galaxies
Recovering 3D Magnetic Turbulence from Single-frequency Faraday Screens
Aliaksandr Melnichenka, Alex Lazarian and Dmitri Pogosyan
Statistics of polarized synchrotron radiation carry information about the properties of the underlying
turbulence. We consider a setup in which synchrotron radiation is emitted in a distant volume and then passes through a turbulent screen that induces Faraday rotation. Using both MHD simulations and synthetic
turbulence spectra, we explore the spectrum of observed polarization directions measured at a single frequency as a diagnostic for recovering the statistics of
turbulence in both the emitting region and the Faraday rotation volume. We compare these results with our analytical expectations. In doing so, we compare the directional spectrum with the wavelength-derivative diagnostic explored earlier by Lazarian & Pogosyan. We demonstrate that the directional spectrum exhibits greater sensitivity to the
turbulence in the Faraday rotation volume. We provide an observer-friendly criterion to determine whether it samples
turbulence in the synchrotron-emitting region or in the Faraday rotation region. These results open a practical pathway for extracting
turbulence statistics from existing and forthcoming single-band
radio polarimetry.
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Instrumentation and Methods for Astrophysics
Electrical coupling of a horizontal dipole antenna to a dielectric half-space: applications to radio astronomy from the lunar surface
Kaja M. Rotermund, Aritoki Suzuki, Stuart D. Bale et al. (+1 more)
The far side of the Moon, shielded from terrestrial
radio frequency interference and beyond the influence of Earth's ionosphere, should offer a uniquely quiet environment for
radio astronomy and cosmological experiments. The
radio sky below 30 MHz is largely unexplored and is thought to contain spectral signatures of new physics in the early, high-
redshift Universe. Achieving precision measurements in this band requires accurate understanding of
antenna performance and systematics. For upcoming lunar surface
radio astronomy missions, this modeling will be challenging because
antennas will deploy at heights that are only a small fraction of a wavelength above the lunar regolith, where strong coupling between the
antenna and the surface can significantly alter impedance, radiation patterns, and efficiency. The challenge is compounded by the layered dielectric structure of the regolith and the tendency for permittivity to increase with depth, both of which are difficult to represent faithfully in numerical simulations. In this work, we review theoretical predictions for the behavior of a simple horizontal dipole above a dielectric half-space, representing the lunar regolith, and compare them with simulation results obtained using the Ansys HFSS integral equation solver. We quantify how the
antenna impedance and beam pattern couple to the sky for a representative lunar surface
radio astronomy experiment. The results show that surface induced effects decrease rapidly, even for modest increases in
antenna height above the regolith. Conversely, a dipole
antenna placed on or very near the lunar surface will exhibit complex spectral response that renders systematics control very difficult without detailed information on regolith properties.
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All authors Kaja M. Rotermund, Aritoki Suzuki, Stuart D. Bale, Anže Slosar
Earth and Planetary Astrophysics
Exocometary physics: material release and tails
Théo Vrignaud, Dennis Bodewits, Jake Hanlon et al. (+5 more)
Despite decades of observations, the physical processes governing mass loss from small bodies beyond our
Solar System remain poorly constrained. These exocomets are often treated as analogs of
Solar System comet, yet the
stellar environments they inhabit spans a wide range in terms of luminosity,
stellar winds, and evolutionary stage, leading to potentially very diverse physical behaviors. Within our
Solar System, small bodies lose material through a range of mechanisms, including sublimation, desorption, impacts, and/or sputtering. Once released, the composition and dynamics of the ejecta are then altered by additional processes, such as
dust sublimation, ionization, and radiation pressure. In extrasolar systems, these mechanisms unfold under vastly different radiative and
plasma conditions, leading to a rich diversity of mass-loss pathways and observable signatures. This work reviews our understanding of the mechanisms driving mass loss from small bodies and the subsequent
evolution of ejecta in diverse
stellar environments. We compare the physical and chemical mechanisms that drive gas and
dust production, and investigate how they scale with
stellar luminosity, temperature, and activity. We then examine the processes that modify the composition of the ejecta (e.g.,
dust sublimation, dissociation, or ionisation) and its dynamics (e.g., radiation pressure or
stellar winds). To illustrate how these processes vary across different
stellar environments, we use four well-studied planetary systems as case studies: the Sun, $\beta$ Pictoris, AU Microscopii, and WD 1145+017. By exploring how cometary tails behave under such diverse conditions, this work provides a physical framework for interpreting exocometary activity and sheds light on why A-type
stars, such as the famous $\beta$ Pictoris, are over-represented in the population of exocomet-hosting
stars.
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All authors Théo Vrignaud, Dennis Bodewits, Jake Hanlon, Matthew M. Knight, Tim D. Pearce, Darryl Z. Seligman, Dimitri Veras, Geraint H. Jones
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
ALP Dark Matter, Cosmological Magnetic Fields and the Direct Collapse Black Hole Formation Scenario
Ashu Kushwaha and Robert Brandenberger
Assuming that dark matter is an ultralight pseudoscalar particle which couples to electromagnetism like an
axion (an ALP), we demonstrate that the coupling of the cosmological
magnetic field produced by the ALP field oscillations to the
primordial dark matter fluctuations yields a spectrum of gauge field fluctuations which can produce a sufficient flux of Lyman-Werner
photons to enable the Direct Collapse Black Hole formation scenario. The induced flux is consistent with the bounds on the excess flux of
radio photons from ARCADE2 and EDGES measurements.
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High Energy Astrophysical Phenomena
Collisionless Accretion of Finite-Angular-Momentum Plasma onto a Spinning Black Hole
John M. Mehlhaff, Alexander Y. Chen, Martin Luepker et al. (+1 more)
In low-luminosity active
galactic nuclei like M87* and Sgr A*, the
accretion disk around the central supermassive black hole is tenuous and collisionless. As a result, the usual ideal magnetohydrodynamics (MHD) approximation may not be applicable. In this Letter, we report on the first fully kinetic simulations of the
accretion process where the
plasma initially has finite angular momentum, focusing on the case of axisymmetry. The simulated
accretion flow behaves remarkably similarly to the magnetically arrested disk (MAD) regime of ideal MHD, reproducing episodes of
magnetic flux saturation and eruption typical of MADs. The resemblance to fluid models owes largely to kinetic instabilities, which regulate pressure anisotropy in the disk, allowing fluid terms to dominate the angular momentum transfer. In addition, by handling
vacuum regions effectively, our kinetic approach probes the matter supply to the jet funnel. We observe no efficient penetration of the accreting material into this region, suggesting that a pair discharge may be required to sustain the Blandford-Znajek process. These initial findings represent important groundwork to be checked and built upon by future kinetic
accretion simulations, especially in 3D.
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All authors John M. Mehlhaff, Alexander Y. Chen, Martin Luepker, Yajie Yuan
High Energy Astrophysical Phenomena
Whistler-Alfvén turbulence in a non-neutral ultrarelativistic pair plasma
Stanislav Boldyrev and Mikhail Medvedev
The large-scale dynamics of most conventional space and astrophysical
plasmas are predominantly governed by Alfvén modes, which are low-frequency magnetohydrodynamic modes existing in magnetized media. At scales smaller than the ion gyroscale or frequencies exceeding the ion cyclotron frequency, the Alfvén modes transform into kinetic-Alfvén or whistler modes that significantly contribute to
plasma dynamics. However, this scenario reverses in non-neutral pair
plasmas, such as those found in the magnetospheres of
pulsars and magnetars, around rotating black holes and in their relativistic jets, as well as in certain laboratory
plasmas. In these systems, the large-scale dynamics is governed by hybrid whistler-Alfvén modes, which transform into pure Alfvén modes at smaller scales. We derive the nonlinear equations that describe the dynamics of whistler-Alfvén modes in ultrarelativistic non-neutral magnetically dominated pair
plasma and discuss the spectrum of
turbulence governed by these equations.
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Astrophysics of Galaxies
Uncovering the absorbed atomic Universe with the [OI]63um line
Carlos De Breuck, Kevin C. Harrington, Wout Hermans et al. (+7 more)
We report the discovery of strongly absorbed [OI]63um in a sample of 12 DSFGs at 4.2<z<5.8 selected from the SPT survey. This is the first systematic survey of the [OI]63um fine-structure line at z>4. Using ALMA Bands 9 and 10, we obtain spatially and spectrally resolved observations that probe the interstellar medium on sub-kpc scales. Despite reaching sensitivities 10-100x deeper than most previous studies, we detect [OI]63um in emission in only 2 sources at low significance, with the remaining
galaxies yielding stringent non-detections over the full velocity range covered by robust detections of other far-infrared lines, including [CII] and [NII]205um. We identify several compact (0.05-0.2") regions having [OI]63um absorption against the far-infrared
dust continuum, some of which are possibly reaching below rest-frame CMB radiation level. We also detect narrow, spatially localised [OI]63um emission "escape channels" preferentially detected in regions with weak or absent
dust continuum emission. We predict that similar absorption effects may appear in the [CII] line, particularly when concentrating on the regions with the densest foreground material along the line of sight. The [OI]63um line appears to be originate from a mix of compact, high optical depth [OI]63um emitting regions and sub-thermally excited, oxygen-rich molecular clouds dispersed throughout high-
redshift starbursts that are capable of absorbing the ground-state line emission. Combined with a comparison to cosmological radiation hydrodynamical simulations, this supports the interpretation that regions with higher gas and
dust column densities may lead to weakening an intrinsically strong [OI]63um line emission. We argue that the high [OI]63um optical depth is the dominant effect causing the strong absorption, limiting the diagnostic power of this line to trace regions of massive
star formation in high-
redshift DSFGs.
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All authors Carlos De Breuck, Kevin C. Harrington, Wout Hermans, Luke Maud, Aniket Bhagwat, Ilse De Looze, Bo Peng, Amit Vishwas, Benedetta Casavecchia, Andreas Lundgren
Astrophysics of Galaxies
Stellar associations powering HII regions $\unicode{x2013}$ II. Escape fraction of ionizing photons
Fabian Scheuermann, Kathryn Kreckel, Jia Wei Teh et al. (+27 more)
Newly formed
stars have a profound impact on their environment by depositing energy and momentum into the surrounding gas. However, only a fraction of the
stellar feedback is retained in the cloud and observational constraints are needed to further our understanding of this process. In a sample of 19 nearby
galaxies, we match HII regions from PHANGS$\unicode{x2013}$MUSE to their ionizing
stellar source from PHANGS$\unicode{x2013}$HST and measure the percentage of ionizing radiation that is leaking into the surrounding diffuse ionized gas (DIG). Based on a catalogue, where each HII region is powered by a single young and massive
stellar association, we measure a
photon escape fraction of $f_\mathrm{esc}=82^{+12}_{-24}$ per cent. Comparable results are obtained when different procedures are used to match the ionized gas to its source. All samples we study contain a substantial fraction of objects (up to 20 per cent), where the
stellar source is not sufficient to produce the H$\alpha$ flux observed from the nebula. Many of them are probably related to uncertain age estimates, but we also find numerous regions, where a significant fraction of the ionizing
photon budget is contributed by
stars that reside outside the boundaries of the HII region. This motivates the use of an alternative
galaxy-wide approach, in which we include all HII regions and
stellar sources, not just the ones that show a clear overlap. When summing up the ionization budget over entire
galaxies, we measure slightly lower, but consistent values.
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All authors Fabian Scheuermann, Kathryn Kreckel, Jia Wei Teh, Francesco Belfiore, Brent Groves, Ashley T. Barnes, Médéric Boquien, Mélanie Chevance, Daniel A. Dale, Oleg Egorov, Simon C. O. Glover, Kathryn Grasha, Stephen Hannon, Ralf S. Klessen, Kirsten L. Larson, Janice C. Lee, Fu-Heng Liang, Laura A. Lopez, J. Eduardo Méndez-Delgado, Justus Neumann, Eve Ostriker, Hsi-An Pan, Lise Ramambason, Francesco Santoro, Eva Schinnerer, David A. Thilker, Qiushi Chris Tian, Leonardo Úbeda, Bradley C. Whitmore, Thomas G. Williams
High Energy Astrophysical Phenomena
Fermi-LAT 16-year Source List
J. Ballet, P. Bruel, T.H. Burnett et al. (+1 more)
The current
Fermi-LAT source catalog (4FGL-DR4: 7194 sources over 14 years) was built incrementally from the 8-year catalog. In a survey mission like
Fermi, data accumulate on each source over time, so after 16 years (reached in August 2024) and twice the data for the original 4FGL sources we have more precise localization (by 24% on average). It is thus time to generate a new original catalog, which implies, beyond adding the sources newly detectable after two more years, changing the existing source names (derived from their coordinates) and reviewing the associations. We present an early 16-year list (FL16Y) of 7220 sources, which relocalizes all sources and improves a few aspects of the catalog analysis, but still uses the same model of interstellar diffuse emission as 4FGL-DR4.
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All authors J. Ballet, P. Bruel, T.H. Burnett, B. Lott
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Choice of Quantum Vacuum for Inflation Observables
Melo Wood-Saanaoui, Rudnei O. Ramos and Arjun Berera
We investigate the modifications to inflationary observables that arise when adopting an $\alpha$-
vacuum instead of the standard Bunch–Davies
vacuum for
quantum fluctuations during inflation. Within the Starobinsky inflationary model, we compute and compare the scalar spectral index, its running, and the running of the running arising from different choices of the initial
vacuum state. We further examine the energy scales associated with $\alpha$-
vacua and argue that, for any number of extra spatial dimensions, the relevant scale can be truncated at the Hubble scale, $\sim$$\mathcal{O}(10^{13})\,\mathrm{GeV}$, without conflict with current Cavendish-type experimental bounds on sub-millimeter
gravity ($\sim$$250\,\mu\mathrm{m}$). Our analysis demonstrates that the $\alpha$-
vacuum is subject to stringent constraints as a viable de~Sitter-invariant alternative to the Euclidean (Bunch–Davies)
vacuum, with the corrections that it induces in the inflationary observables being strongly limited by the latest Planck data.
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High Energy Astrophysical Phenomena
Forward hadron production in proton-air collisions above LHC energies through the fluctuations of extensive air showers
Lorenzo Cazon, Ruben Conceição, Miguel Alexandre Martins et al. (+1 more)
Primary
proton-air interactions at ultra-high energies leave a physically interpretable imprint on the correlated fluctuations of the depth of shower maximum and the
muon content in extensive air showers. This imprint reflects the stochasticity in the partition of the primary energy among secondary particles in the first interaction. We show that these fluctuations can be accessed through a probabilistic description that isolates sensitivity to hadronic physics in the initial collision, while treating the subsequent shower development as effectively universal. The uncertainties resulting from this universality are smaller than the spread among current hadronic interaction models and comparable to current experimental uncertainties. Consequently, the joint observable space defined by these two quantities provides a new probe of
hadron production in kinematic regimes far beyond the reach of human-made accelerators.
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All authors Lorenzo Cazon, Ruben Conceição, Miguel Alexandre Martins, Felix Riehn
Astrophysics of Galaxies
Overlap Zoo Beta: A Catalogue of ~800 Occulting Pairs in the DESI Legacy Survey using Citizen Science
T. Butrum, B. Holwerda, W. C. Keel et al. (+11 more)
Overlapping
galaxies, in which a foreground
galaxy partially overlaps a background
galaxy, offer a unique opportunity to measure
dust attenuation, a key nuisance parameter in
galaxy studies, empirically and in great detail by modelling the light of both the foreground and background
galaxy and inferring the missing light in the overlapping region. However, the current catalogue of overlapping pairs is relatively limited in number compared to catalogues dedicated to individual
galaxies. Expanding this catalogue is not only a necessity to facilitate further detailed
dust studies beyond the few limited studies conducted thus far, but also to improve pair-to-pair variance and support automated identification through machine learning techniques. To achieve this, we utilise
galaxies classified as "overlapping" from
Galaxy Zoo DECaLS (GZD-1, -2, and -5), along with images from Data Release 10 (DR10) of the DESI Legacy Survey, in our individual citizen science project to classify these pairs directly using volunteers. This new catalogue will not only provide a wealth of targets for future
dust studies but will also contribute to a deeper understanding of these pairs and
dust as a whole.
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All authors T. Butrum, B. Holwerda, W. C. Keel, C. Robertson, I. Castellano, S. Pandey, S. M. R. Adnan, L. C. Bills, D. Patel, K. Cook, T. Hardin, A. Palao, B. Connelly, M. Morton
Earth and Planetary Astrophysics
Survival of Protoplanetary Disks in Upper Scorpius from Population Synthesis Models with External Photoevaporation
Jingyi Ping, Rossella Anania, Paola Pinilla et al. (+1 more)
We present population synthesis models of viscous protoplanetary disks subject to mild external far-ultraviolet (FUV) radiation fields ($F_{\rm UV}=1\text{-}100\,$G$_0$). Our simulations focus on gas disk
evolution, exploring
stellar masses drawn from an Initial Mass Function and a range of initial disk conditions. We quantify the fraction of surviving disks across $10\,\mathrm{Myr}$ of
evolution, track the
evolution of gas disk mass and size, and compare our results with observations of protoplanetary disks in the Upper Scorpius region, including the ten targets studied by the AGE-PRO ALMA Large Program. We find that models combining viscous
evolution with external photoevaporation yield disk lifetimes of $3\text{-}7\,\mathrm{Myr}$, consistent with observed dispersal timescales, particularly for $10^{-4} \leq \alpha \leq 10^{-2}$. Low-mass
stars ($0.1\,$M$_\odot$) are more susceptible to disk dispersal due to their weaker gravitational binding, with their fraction among all surviving disks dropping from $76\%$ at birth to $51\%$ by $10\,\mathrm{Myr}$. The majority of the long-lived disks are those with low viscosity $\alpha < 10^{-3.5}$ and initial characteristic radius $R_c < 125\,\mathrm{AU}$, while the initial disk-to-
star mass ratio does not play an important role. The median gas disk mass and radius of the surviving disks exhibit a sharp decline in the first $0.2\,\mathrm{Myr}$ of
evolution, followed by a slight increase that reflects survivorship bias. We also explore correlations between gas disk mass and size vs.
stellar mass and FUV strength. Our findings highlight the critical role of external photoevaporation in shaping disk populations even at moderate levels of FUV radiation fields.
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All authors Jingyi Ping, Rossella Anania, Paola Pinilla, Miguel Vioque
Solar and Stellar Astrophysics
Dynamical masses of YSOs with the VLBA: DYNAMO VLBA: Trigonometric parallaxes and proper motions of YSOs in Orion
Sergio A. Dzib, Jazmín Ordóñez-Toro, Laurent Loinard et al. (+9 more)
We present results from a multi-epoch Very Long Baseline Array (VLBA) survey of compact
radio sources in the Orion complex, conducted within both the DYNAMO-VLBA and the GOBELINS projects. Our observations detected 216 compact
radio sources, of which 58 yielded reliable multi-epoch astrometric solutions. For these sources, we derived trigonometric parallaxes and proper motions with typical precisions of about 0.05 mas and 0.10 mas yr$^{-1}$, respectively. The measured parallaxes range between 2.26 and 2.65 mas, corresponding to distances of 380 - 440 pc, and delineate the depth of the Orion
star-forming complex. We determine mean distances of $405\pm16$ pc for NGC 2068, $403\pm5$ pc for NGC 2024, $407\pm12$ pc for the $\sigma$ Orionis region, $388.5\pm1.7$ pc for the Orion Nebula Cluster (ONC), and $438\pm12$ pc for L1641. A comparison with
Gaia DR3 astrometry for 28 common sources reveals negligible mean parallax offsets ($\Delta\varpi=-0.02\pm0.01$ mas) and small systematic differences in proper motions ($\sim$0.07 mas yr$^{-1}$), likely due to residual rotation of the
Gaia reference frame. Our results demonstrate the capability of high-precision
radio astrometry to map embedded
stellar populations and to provide an independent calibration of the
Gaia reference system in obscured regions.
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All authors Sergio A. Dzib, Jazmín Ordóñez-Toro, Laurent Loinard, Marina Kounkel, Gisela Ortiz-Leon, Phillip A. B. Galli, Luis F. Rodríguez, Amy J. Mioduszewski, Josep M. Masqué, Eoin O'Kelly, Jan Forbrich, Karla Moo-Herrera
High Energy Astrophysical Phenomena
IGR J12580+0134: A Possible Repeated Partial Tidal Disruption Event Inferred from Late-Time Radio Re-brightenin
Po Ma, Shao-Yu Fu, Linhui Wu et al. (+2 more)
Repeating partial
tidal disruption events (pTDEs) provide a direct probe of
stellar orbits and episodic mass loss around supermassive black holes, but robust identification requires multi-band and multi-epoch evidence. %consistent with a single physical origin. We investigate whether the late-time
radio rebrightening of the
nuclear transient IGR~J12580+0134 in NGC~4845 can be explained as a repeating pTDE, using multi-epoch Karl G.\ Jansky VLA observations together with X-ray constraints from Swift/XRT and NICER. Through a systematic analysis of the
radio data, we identify two well-defined
radio flares and a possible third late-time rebrightening
flare. Modeling the second
flare with a synchrotron afterglow framework using Markov Chain Monte Carlo fitting is consistent with a sub-relativistic
outflow with a characteristic velocity of order ${v \simeq 0.3c}$, an isotropic-equivalent kinetic energy of order ${10^{50}}$ erg, and an approximately constant-density circumnuclear medium. No significant contemporaneous brightening is detected by Swift/XRT during the 2016
radio flare, while faint NICER
flares in 2023 suggest intermittent low-level
accretion. We also considered several possible interpretations for the late-time
radio rebrightening, and found that the repeated pTDE scenario provides a more natural overall explanation for the observed phenomenology. Given the currently sparse data coverage, continued sensitive
radio and X-ray monitoring will be essential to test this interpretation and to search for future reactivations.
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All authors Po Ma, Shao-Yu Fu, Linhui Wu, Wei-Hua Lei, Qiang Yuan
Astrophysics of Galaxies
Optical Spectroscopy of Dwarf Galaxies at $z\sim 0.15$ in the COSMOS Field: Star Formation and Dust Properties
Zahra Sattari, Daniel D. Kelson, Bahram Mobasher et al. (+4 more)
We present a spectroscopic study of low-mass
galaxies (LMGs;$10^8\leq\rm M_*/M_\odot\leq10^9$) at $z\sim0.15$ in COSMOS field, and compare it to a control sample of intermediate-mass
galaxies (IMGs;$10^9\leq\rm M_*/M_\odot\leq10^{10}$) at $z\sim0.35$. We examine their
star formation rates (SFRs),
dust attenuation properties, and the relationship between nebular and
stellar reddening. For both samples, SFRs derived from H$\alpha$ are strongly correlated with SFRs from fitting simple
star formation histories (SFHs) to the
galaxies' spectral energy distributions. In fitting a joint SFR-$\rm M_*$ relation, we obtain a slope of $\rm {\Delta log(SFR_{H\alpha})}/{\Delta log(M_*/M_\odot)}=1.01\pm0.03$, indicating that fair ensembles of SFHs for
galaxies at these
stellar masses are well-described by scale-free, self-similar forms. We also examine their
dust attenuation properties and the relationship between nebular and
stellar reddening, exploring how these quantities vary with
stellar mass and specific SFR (sSFR). Nebular attenuation increases with
stellar mass for IMGs but is lower and less mass-dependent in LMGs, consistent with their reduced
dust content. In all cases,
stellar continuum attenuation is lower than nebular attenuation, as expected from the two-component
dust model. The nebular-to-
stellar color excess ratio in both samples is consistent with the canonical factor of 2.27. The ratio is mass-independent, but rises with sSFR in IMGs and remains constant in LMGs. These results suggest that in LMGs, efficient dispersal of birth clouds keeps the differential attenuation approximately constant across sSFR. Thus, although LMGs follow the same global SFR-$\rm M_*$ scaling as massive
galaxies, their lower
dust content and feedback-maintained ISM produce distinct attenuation behavior relative to IMGs.
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All authors Zahra Sattari, Daniel D. Kelson, Bahram Mobasher, Nima Chartab, Vihang Mehta, Harry I. Teplitz, Shannon G. Patel
Solar and Stellar Astrophysics
MESA Isochrones and Stellar Tracks. II. Models with alpha-enhanced chemical composition
A Dotter, E Bauer, MJ Park et al. (+4 more)
We update and expand the MESA Isochrones and
Stellar Tracks (MIST) database to include variations in the alpha-capture elements, specifically [alpha/Fe]=-0.2, 0, +0.2, +0.4, and +0.6 for -3 <= [Fe/H] <= +0.5. Variations in [alpha/Fe] are included in a self-consistent manner from the
stellar interior models to the synthetic spectra used to translate these models in the observational plane. We describe a number of updates to the physics utilized in these models as well as new information provided by the models. We validate the models with comparisons to other
stellar evolution models including the previous generation of MIST and other models from the literature. MIST data products including
stellar evolutiont tracks, isochrones, and bolometric correction tables can be obtained from the MIST project website, https://mist.science. All necessary files to reproduce MIST models are available from Zenodo.
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All authors A Dotter, E Bauer, MJ Park, C Conroy, A Milone, M Joyce, M Cantiello