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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 8 October

Astrophysics of Galaxies

Composition of planetary debris around the white dwarf GD 362

William T. Reach, Mukremin Kilic, Carey M. Lisse et al. (+9 more)

White dwarf stars with high abundances of heavy elements in their atmospheres and infrared excesses are believed to be accreting planetary material. GD 362 is one of the most heavily polluted white dwarfs and has an exceptionally strong mid-infrared excess, reprocessing 2.4% of the star's light into the mid-infrared. We present a high signal-to-noise, medium-resolution spectrum of GD 362 obtained with JWST, covering 0.6 to 17 microns, along with photometry out to 25.5 microns. The mid-infrared spectrum is dominated by an exceptionally strong 9 to 11 micron silicate feature, which can be explained by a combination of olivine and pyroxene silicate minerals. Grains such as carbon, hotter than silicates, are required to explain the near-infrared emission. The silicates and carbon reside in a disk from 140 to 1400 stellar radii, and the disk scale height is greater than half the stellar radius. The elemental abundances of the solid material, relative to Si, are within a factor of 2 of meteoritic (CI chondrites) for C, O, Mg, Al, and Fe, with Al elevated and O slightly depleted. A similar pattern is observed for the abundances of accreted material in the stellar photosphere. Hydrogen is an exception, because no significant H-bearing minerals or water were detected in the disk, despite a large H abundance in the photosphere.
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All authors William T. Reach, Mukremin Kilic, Carey M. Lisse, John H. Debes, Ted von Hippel, Bianca Azartash-Namin, Loic Albert, Susan E. Mullally, Fergal Mullally, Misty Cracraft, Madison Bernice, Selin L. Erickson

Earth and Planetary Astrophysics

An Automated Probabilistic Asteroid Prediscovery Pipeline

Sage Li, Alex Geringer-Sameth and Nathan Golovich

We present an automated and probabilistic method to make prediscovery detections of near-Earth asteroids (NEAs) in archival survey images, with the goal of reducing orbital uncertainty immediately after discovery. We refit the Minor Planet Center's astrometry and propagate the full six-parameter covariance to survey epochs to define search regions. We build low-threshold source catalogs for viable images and evaluate every detected source in a search region as a candidate prediscovery. We eliminate false positives by refitting a new orbit to each candidate and probabilistically linking detections across images using a likelihood ratio. Applied to Zwicky Transient Facility (ZTF) imaging, we identify approximately 3000 recently discovered NEAs with prediscovery potential, including a doubling of the observational arc for about 500. We use archival ZTF imaging to make prediscovery detections of the potentially hazardous asteroid 2021 DG1, extending its arc by 2.5 yr and reducing future apparition sky plane uncertainty from many degrees to arcseconds. We also recover 2025 FU24 nearly 7 yr before its first known observation, when its sky plane uncertainty covers hundreds of square degrees across thousands of ZTF images. The method is survey agnostic and scalable, enabling rapid orbit refinement for new discoveries from Rubin, NEO Surveyor, and NEOMIR.
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Solar and Stellar Astrophysics

Good things always come in 3s: trimodality in the binary black-hole chirp-mass distribution supports bimodal black-hole formation

Reinhold Willcox, Fabian R. N. Schneider, Eva Laplace et al. (+7 more)

The latest GWTC-4 release from the LIGO-Virgo-KAGRA (LVK) collaboration nearly doubles the known population of double compact object mergers and reveals a new trimodal structure in the chirp-mass distribution of merging binary black holes (BBHs) below 30 Msun. Recent detailed stellar evolution models show that features in the pre-collapse cores of massive stars produce a bimodal black hole (BH) mass distribution, which naturally extends to a trimodal BBH chirp-mass distribution. Both distributions depend only weakly on metallicity, implying universal structural features which can be tested with LVK observations. Using a new compact-remnant mass prescription derived from these models, we perform rapid population synthesis simulations to test the robustness of the predicted chirp-mass structure against uncertainties in binary evolution and cosmic star formation history, and compare these results with the current observational data. The trimodal chirp-mass distribution emerges as a robust outcome of the new remnant-mass model, persisting across variations in binary and cosmic physics. In contrast, traditional BH formation models lacking a bimodal BH mass spectrum fail to reproduce the observed trimodality. The updated models also predict lower BBH merger rates by a factor of a few, in closer agreement with LVK constraints. Intriguingly, the central chirp-mass peak, dominated by unequal-mass BBHs, originates from a previously underappreciated formation pathway in which strong luminous blue variable winds suppress binary interaction before the first BH forms. If isolated binary evolution dominates BBH formation below 30 Msun, the relative heights of the three chirp-mass peaks offer powerful observational constraints on core collapse, BH formation, binary evolution, and cosmic star formation. These universal structural features may also serve as standard sirens for precision cosmology.
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All authors Reinhold Willcox, Fabian R. N. Schneider, Eva Laplace, Philipp Podsiadlowski, Kiril Maltsev, Ilya Mandel, Pablo Marchant, Hugues Sana, Tjonnie G. F. Li, Thomas Hertog

Astrophysics of Galaxies

Bar pattern speed modulation across LMC stellar populations

V. Araya, L. Chemin, O. Jimenez-Arranz et al. (+1 more)

The bar pattern speed of the LMC has been measured using Gaia data, suggesting the presence of a slow pattern, perhaps not rotating at all. Numerical simulations of interacting LMC-SMC systems were able to reproduce a bar stoppage. Here, we report on the first measurement of the bar pattern speed of the LMC as a function of the evolutionary phase of its stellar populations. Astrometric and photometric data of 11 million LMC stars from Gaia DR3 were used to build five evolutionary phases, from less to more evolved stars. The Dehnen method, a new procedure to derive bar pattern speeds from kinematics of particles in N-body simulations, is applied to the LMC stellar populations. We observe a modulation of the bar pattern speed with the evolutionary phase, meaning that different LMC stellar populations exhibit different pattern speeds, ranging from -0.9 to 6.6 km/s/kpc. Moreover, less evolved stars have a lower pattern speed while the bar of more evolved phases tends to rotate faster. The LMC bar is thus extremely slow, ruling out the presence of bar corotation within the disc, in agreement with a previous claim, but this time observed with various stellar populations. It is the first time that a pattern speed is measured separately for different stellar populations in any galaxy. The LMC pattern speed cannot be simply resumed to a singular value, but instead is an overlay of different patterns depending on the evolutionary phase of the stars. Future Gaia releases will be crucial to investigate more deeply the relations of the pattern speed with important astrophysical parameters of stars, like their age and metallicity, which will be helpful to constrain the chemo-dynamical evolution of the LMC bar.
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All authors V. Araya, L. Chemin, O. Jimenez-Arranz, M. Romero-Gomez

High Energy Astrophysical Phenomena

Evidence for Supermassive Black Hole Binaries

Martin G. H. Krause, Martin A. Bourne, Silke Britzen et al. (+10 more)

We review the state of the evidence for the existence and observational appearance of supermassive black hole binaries. Such objects are expected from standard hierarchical galaxy evolution to form after two galaxies, each containing a supermassive black hole, have merged, in the centre of the merger remnant. A complex interaction is predicted to take place with stars and gas in the host galaxy, leading to observable signatures in weakly as well as actively accreting phases. Direct observational evidence is available and shows examples of dual active galactic nuclei from kpc scales down to parsec scales. Signatures of possibly closer supermassive black hole binaries may be seen in jetted black holes. The interaction with stars and gas in a galaxy significantly affects the hardening of the binary and hence contributes to uncertainties of the expected gravitational wave signal. The Laser Interferometer Space Antenna (LISA) should in the future detect actual mergers. Before the launch of LISA, pulsar timing arrays may have the best chance to detect a gravitational wave signal from supermassive black hole binaries. The first signs of the combined background of inspiralling objects might have been seen already.
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All authors Martin G. H. Krause, Martin A. Bourne, Silke Britzen, Adi Foord, Jenny E. Greene, Melanie Habouzit, Maya A. Horton, Lucio Mayer, Hannah Middleton, Rebecca Nealon, Julia M. Sisk-Reynés, Christopher S. Reynolds, Debora Sijacki

Astrophysics of Galaxies

Robust Measurement of Stellar Streams Around the Milky Way: Correcting Spatially Variable Observational Selection Effects in Optical Imaging Surveys

K. K. Boone, P. S. Ferguson, M. Tabbutt et al. (+47 more)

Observations of density variations in stellar streams are a promising probe of low-mass dark matter substructure in the Milky Way. However, survey systematics such as variations in seeing and sky brightness can also induce artificial fluctuations in the observed densities of known stellar streams. These variations arise because survey conditions affect both object detection and star–galaxy misclassification rates. To mitigate these effects, we use Balrog synthetic source injections in the Dark Energy Survey (DES) Y3 data to calculate detection rate variations and classification rates as functions of survey properties. We show that these rates are nearly separable with respect to survey properties and can be estimated with sufficient statistics from the synthetic catalogs. Applying these corrections reduces the standard deviation of relative detection rates across the DES footprint by a factor of five, and our corrections significantly change the inferred linear density of the Phoenix stream when including faint objects. Additionally, for artificial streams with DES like survey properties we are able to recover density power spectra with reduced bias. We also find that uncorrected power-spectrum results for LSST-like data can be around five times more biased, highlighting the need for such corrections in future ground based surveys.
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All authors K. K. Boone, P. S. Ferguson, M. Tabbutt, K. Bechtol, T.-Y. Cheng, A. Drlica-Wagner, C. E. Martínez-Vázquez, B. Mutlu-Pakdil, T. M. C. Abbott, O. Alves, F. Andrade-Oliveira, D. Bacon, S. Bocquet, D. Brooks, R. Camilleri, A. Carnero Rosell, L. N. da Costa, M. E. da Silva Pereira, T. M. Davis, J. De Vicente, S. Desai, P. Doel, S. Everett, B. Flaugher, J. Frieman, J. García-Bellido, D. Gruen, G. Gutierrez, S. R. Hinton, D. L. Hollowood, K. Honscheid, D. J. James, K. Kuehn, J. L. Marshall, J. Mena-Fernández, F. Menanteau, R. Miquel, J. Myles, R. L. C. Ogando, A. A. Plazas Malagón, A. Porredon, M. Rodríguez-Monroy, E. Sanchez, D. Sanchez Cid, I. Sevilla-Noarbe, M. Smith, E. Suchyta, M. E. C. Swanson, V. Vikram, N. Weaverdyck

Solar and Stellar Astrophysics

Characterization of the Trans-Alfvénic Region Using Observations from Parker Solar Probe

Subash Adhikari, Riddhi Bandyopadhyay, Joshua Goodwill et al. (+14 more)

Close to Earth the solar wind is usually super-Alfvénic, i.e. the speed of the solar wind is much larger than the Alfvén speed. However, in the lower coronal regions, the solar wind is mostly sub-Alfvénic. With the Parker Solar Probe (PSP) crossing the boundary between the sub- and super-Alfvénic flow, Bandyopadhyay et al. (2022) performed a turbulence characterization of the sub-Alfvénic solar wind with initial data from encounters 8 and 9. In this study, we re-examine the turbulence properties such as turbulence amplitude, anisotropy of the magnetic field variance, intermittency and switchback strength extending with PSP data for encounters 8-19. The later orbits probe lower altitudes and experience sub-Alfvénic conditions more frequently providing a greater statistical coverage to contrast sub- and super-Alfvénic solar wind. Also, by isolating the intervals where the solar wind speed is approximately equal to the Alfvén speed, we explore the transition in more detail. We show that the amplitude of the normalized magnetic field fluctuation is smaller for the sub-Alfvénic samples. While solar wind turbulence in general is shown to be anisotropic, the sub-Alfvénic samples are more anisotropic than the super-Alfvénic samples, in general. Further, we show that the sub- and super-Alfvénic samples do not show much distinction in terms of intermittency strength. Finally, consistent with prior results, we find no evidence for polarity reversing > 90 degrees switchbacks in the sub-Alfvénic solar wind
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All authors Subash Adhikari, Riddhi Bandyopadhyay, Joshua Goodwill, William H. Matthaeus, David Ruffolo, Panisara Thepthong, Peera Pongkitiwanichakul, Sohom Roy, Francesco Pecora, Rohit Chhiber, Rayta Pradata, Arcadi Usmanov, Michael Stevens, Samuel Badman, Orlando Romeo, Jiaming Wang, Melvyn L. Goldstein

Astrophysics of Galaxies

LATIS: Galaxy-Environment Relations at Cosmic Noon and the Role of Sample Selection

Nima Chartab, Andrew B. Newman, Gwen C. Rudie et al. (+6 more)

We investigate the environmental dependence of galaxy properties at $z\sim2.5$ using the Ly$\alpha$ Tomography IMACS Survey (LATIS), which provides high-resolution three-dimensional maps of intergalactic medium (IGM) overdensity via Ly$\alpha$ forest tomography. Our analysis focuses on a UV-selected spectroscopic sample of 2185 galaxies from LATIS and a complementary set of 1157 galaxies from heterogeneous spectroscopic surveys in the COSMOS field. We compare these datasets to forward-modeled mock catalogs constructed from the IllustrisTNG300-1 simulation, incorporating realistic selection functions to match both LATIS and the literature sample. While the mass-complete simulation predicts strong environmental trends–more massive and quiescent galaxies preferentially occupy overdense regions–we find that such trends are significantly weaker or absent in the observed samples. The LATIS galaxies show no measurable correlation between specific star formation rate (sSFR) and IGM overdensity, a result reproduced by LATIS-like mock catalogs, confirming that UV selection systematically excludes passive and dusty galaxies in dense environments. The literature compilation, despite improved high-mass coverage, remains incomplete and affected by similar biases. We also analyze a mass-complete photometric sample from the COSMOS-Web catalog at $z\sim2.5$ and find no detectable sSFR-environment relation, a null result that our simulations indicate can be explained by photometric redshift uncertainties. In particular, we find no evidence for a reversal of the sSFR-density relation at cosmic noon. These results demonstrate that observed correlations can be heavily shaped by selection effects, and caution against inferring physical trends from incomplete spectroscopic samples. Deeper, more representative spectroscopic surveys are needed to robustly characterize environmental effects at this epoch.
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All authors Nima Chartab, Andrew B. Newman, Gwen C. Rudie, Guillermo Blanc, Daniel D. Kelson, Mahdi Qezlou, Simeon Bird, Brian C. Lemaux, Olga Cucciati

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Sterile neutrino dark matter from a TeV Scale Seesaw

Kunal Pandey and Suhail Khan

In this article, we investigate the phenomenological aspects of a feebly interacting sterile neutrino dark matter candidate within a low-scale seesaw framework. The Type-I seesaw model is augmented by a second complex scalar doublet ($\Phi_{\nu}$), which couples exclusively to the heavy right-handed neutrinos and the lepton doublet, thereby generating the neutrino Dirac mass term while the first scalar doublet is responsible for giving mass to the remaining Standard Model particles. The lightest sterile neutrino ($N_1$) acts as a feebly interacting massive particle (FIMP), produced via decays of $W^\pm$, $Z$ and extra scalars present in the setup. We point out that $W^\pm$ and $Z$ contributions were overlooked in the previous studies, which actually dominate the $N_1$ production by a factor of $\sim 10^{13}$ and solely determines the relic abundance. Incorporating them leads to several novel consequences for the DM phenomenology like a new non-thermal condition which leads to smaller Yukawa couplings. We thoroughly discuss about the enhancement possibilities of $N_1$'s mass which is controlled by the small vacuum expectation value ($v_{\nu}$) of the second Higgs doublet. After incorporating the latest Lyman-$\alpha$ forest observations, this setup can accommodate both warm and cold dark matter scenarios.
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Earth and Planetary Astrophysics

Enhanced Pebble Drift Across Planet-Opened Gaps in Windy Protoplanetary Disks

Lorraine Nicholson and Jaehan Bae

When a giant planet forms in a protoplanetary disks, it carves a gap around its orbit separating the disk into two parts: inner disk and outer disk. Traditional disk accretion models, which assume material transport is driven by viscosity, reveal that the planet-induced gap acts like a filter which blocks large dust grains from flowing into the inner disk. However, there is growing evidence that material transport may be driven by magnetically-driven winds instead. By carrying out a suite of two-dimensional multi-fluid hydrodynamic simulations where wind is implemented with a parameterized model, we explored how dust filtration efficiency and the size of dust grains filtered change in disks where gas accretion is dominated by magnetically-driven winds. We found that the inward gas flow driven by the wind can enable dust to overcome the pressure bump at the outer gap edge and penetrate the planet-induced gap. The maximum size of dust grains capable of penetrating the gap increasing with the wind strength. Notably, we found that when wind is strong (mass loss rate = 1e-7 M_sun/yr), mm-sized grains can penetrate the gap opened by a multi-Jovian-mass planet. Our results suggest that magnetically driven winds can significantly enhance pebble drift and impact planet formation in the inner protoplanetary disk.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

On the consistent disformal couplings to fermions

Guillem Domènech, Alexander Ganz and Apostolos Tsampodimos

Disformal couplings to fermions lead to a unique derivative coupling to the axial fermionic current, which contains higher derivatives in general. We derive general conditions on consistent disformal couplings by requiring the absence of higher time derivatives, as they typically lead to ghost degrees of freedom. For a two-scalar field disformal transformation, we show that the consistent disformal coupling must have a degenerate field space metric. This allows us to explore consistent, new two-scalar field modified gravity models. We show that the transformation of the Einstein-Hilbert action leads to two-field Horndeski or two-field DHOST theories. Our formalism also applies to disformal transformations with higher derivatives. We derive the consistent subclasses of disformal transformations that include second derivatives of a scalar field and first derivatives of a vector field that lead to generalized U-DHOST and degenerate beyond generalized Proca theories.
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Astrophysics of Galaxies

Is Liller 1 a building block of the Galactic bulge? – Evidence with APOGEE

Anna Liptrott, Ricardo P. Schiavon, Andrew C. Mason et al. (+10 more)

Liller 1 is a stellar system orbiting within the inner 0.8kpc of the Galactic centre, characterised by a wide spread in age and metallicity, indicating a high mass. Liller 1 has been proposed to be a major contributor to the stellar mass of the Galactic bulge, yet its origin is subject to debate. We employ Sloan Digital Sky Survey IV (SDSS-IV) data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) to test scenarios proposed to explain the nature of Liller 1. Using a random sampling technique, we contrast the chemical compositions of Liller 1 stellar members with those of the bulge, inner disc, outer disk and solar neighbourhood. The chemistry of Liller 1 deviates from that of the bulge population at the 2-3$\sigma$ level for $\alpha$-elements Mg, Si, and Ca. We conclude that the progenitor of Liller 1 was not a major contributor of stellar mass to the bulge. Furthermore, we find the abundance pattern of Liller 1 to deviate at the 2$\sigma$ level from that of inner disk stars, ruling out the cluster rejuvenation scenario. Finally, we find that Liller 1 is chemically distinct from solar and outer disc populations, suggesting that the progenitor of Liller 1 is unlikely to be an in-situ massive clump formed at high redshift, from disc gravitational instabilities, that migrated inwards and coalesced with others into the bulge. Finally, we suggest that Liller 1 is a minor contributor to the stellar mass of the inner Galaxy, possibly of extragalactic origin.
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All authors Anna Liptrott, Ricardo P. Schiavon, Andrew C. Mason, Sebastian Kamann, Borja Anguiano, Roger E. Cohen, José G. Fernández-Trincado, Danny Horta, Steven R. Majewski, Dante Minniti, David M. Nataf, Michael J. W. O'Connor, Dominic Wearne

Astrophysics of Galaxies

The evolution of the bar fraction and bar lengths in the last 12 billion years

Zoe A. Le Conte, Dimitri A. Gadotti, Leonardo Ferreira et al. (+7 more)

We investigate the evolution of the bar fraction and length using an extended JWST NIRCam imaging dataset of galaxies at $1 \leq z \leq 4$. We assess the wavelength dependence of the bar fraction and bar length evolution by selecting a nearly mass-complete CEERS disc sample and performing visual classifications on the short (F200W) and long (F356W+F444W) wavelength channels. A similar bar fraction is observed for both samples, and combined, we find a declining bar fraction from $0.16^{+0.03}_{-0.03}$ to $0.07^{+0.03}_{-0.01}$ over the redshift range. No evolution in the F356W+F444W bar length is measured, with a mean of 3.6 kpc. A slight increase of $\sim 1$ kpc towards $z = 1$ is measured in the F200W sample, with a mean of 2.9 kpc. We find that the correlation between bar length and galaxy mass, for massive galaxies at $z < 1$, is unseen at $z > 1$. By incorporating barred galaxies at $z<1$, we show that there is a modest increase in the bar length ($\approx 2$ kpc) towards $z=0$, but bars longer than $\approx8$ kpc are only found at $z<1$. We show that bars and discs grow in tandem, for the bar length normalised by disc size does not evolve. Not only is a significant population of bars forming beyond $z = 1$, but our results also show that some of these bars are as long and strong as the average bar at $z\approx0$.
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All authors Zoe A. Le Conte, Dimitri A. Gadotti, Leonardo Ferreira, Christopher J. Conselice, Camila de Sá-Freitas, Taehyun Kim, Justus Neumann, Francesca Fragkoudi, E. Athanassoula, Nathan J. Adams

Astrophysics of Galaxies · Cross-listed from gr-qc

Can Relativistic Effects explain Galactic Dynamics without Dark Matter?

L. Filipe O. Costa and José Natário

We show that, contrary to some recent claims, relativistic effects cannot mimic dark matter in the galactic rotation curves and gravitational lensing.

Astrophysics of Galaxies · Cross-listed from gr-qc

On defining astronomically meaningful Reference Frames in General Relativity

L. Filipe O. Costa, Francisco Frutos-Alfaro, José Natário et al. (+1 more)

In a recent paper we discussed when it is possible to define reference frames nonrotating with respect to distant inertial reference objects (extension of the IAU reference systems to exact general relativity), and how to construct them. We briefly review the construction, illustrating it with further examples, and caution against the recent misuse of zero angular momentum observers (ZAMOs).
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All authors L. Filipe O. Costa, Francisco Frutos-Alfaro, José Natário, Michael Soffel

Solar and Stellar Astrophysics

Neutrinos from stars in the Milky Way

Pablo Martínez-Miravé and Irene Tamborra

Neutrinos are produced during stellar evolution by means of thermal and thermonuclear processes. We model the cumulative neutrino flux expected at Earth from all stars in the Milky Way: the Galactic stellar neutrino flux (GS$\nu$F). We account for the star formation history of our Galaxy and reconstruct the spatial distribution of Galactic stars by means of a random sampling procedure based on Gaia Data Release 2. We use the stellar evolution code $\texttt{MESA}$ to compute the neutrino emission for a suite of stellar models with solar metallicity and zero-age-main-sequence mass between $0.08M_\odot$ and $100\ M_\odot$, from their pre-main sequence phase to their final fates. We then reconstruct the evolution of the neutrino spectral energy distribution for each stellar model in our suite. The GS$\nu$F lies between $\mathcal{O}(1)$ keV and $\mathcal{O}(10)$ MeV, with thermal (thermonuclear) processes responsible for shaping neutrino emission at energies smaller (larger) than $0.1$ MeV. Stars with mass larger than $\mathcal{O}(1\ M_\odot)$, located in the thin disk of the Galaxy, provide the largest contribution to the GS$\nu$F. Moreover, most of the GS$\nu$F originates from stars distant from Earth about $5-10$ kpc, implying that a large fraction of stellar neutrinos can reach us from the Galactic Center. Solar neutrinos and the diffuse supernova neutrino background have energies comparable to those of the GS$\nu$F, challenging the detection of the latter. However, directional information of solar neutrino and GS$\nu$F events, together with the annual modulation of the solar neutrino flux, could facilitate the GS$\nu$F detection; this will kick off a new era for low-energy neutrino astronomy, also providing a novel probe to discover New Physics.
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Astrophysics of Galaxies

Unified Spectrospatial Forward Models: Spatially Continuous Maps of Weak Emission Lines in the Rosette Nebula with SDSS-V LVM

Thomas Hilder, Andrew R. Casey, Julianne J. Dalcanton et al. (+14 more)

Analyses of IFU data are typically performed on a per-spaxel basis, with each spectrum modelled independently. For low signal-to-noise (S/N) features such as weak emission lines, estimating properties is difficult and imprecise. Arbitrary binning schemes boost S/N at the cost of resolution, and risk introducing biases. We present a general forward-modelling approach that assumes spectra close on the sky are more similar than distant ones, and so can be modelled jointly. These "spectrospatial" models exploit spatial correlation to provide robust inferences, while simultaneously providing continuous predictions of line properties like strength and kinematics across the sky. Instrumental and calibration systematics are straightforward to include and infer. The model provides a natural trade-off between spatial resolution and S/N in a data-driven way. We apply this to Sloan Digital Sky Survey V (SDSS-V) Local Volume Mapper (LVM) data of the Rosette Nebula, producing continuous maps of fluxes and kinematics for Balmer, nebular, and auroral lines, as well as weak C II and N II recombination lines, demonstrating the approach across three orders of magnitude in S/N, including in the very low-S/N regime. The method recovers identical morphologies across different lines tracing similar ionisation volumes, at varying resolutions set by the S/N. We additionally provide a general framework for building and fitting such models in JAX, suitable for many applications. The implementation is fast and memory efficient, scales to large data volumes as in LVM, and can be deployed on hardware accelerators.
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All authors Thomas Hilder, Andrew R. Casey, Julianne J. Dalcanton, Kathryn Kreckel, Amelia M. Stutz, Amrita Singh, Guillermo A. Blanc, Sebastián F. Sánchez, J. E. Méndez-Delgado, Andrew K. Saydjari, Luciano Vargas-Herrera, Niv Drory, Dmitry Bizyaev, José G. Fernández-Trincado, Carlos G. Román-Zúñiga, Juna A. Kollmeier, Evelyn J. Johnston

Astrophysics of Galaxies

A multiscale evolutionary study of molecular gas in STARFORGE. I. Synthetic observations of SEDIGISM-like molecular clouds

K.R. Neralwar, D. Colombo, S. Offner et al. (+6 more)

Molecular clouds are active sites of star formation in galaxies, and their formation and evolution are largely affected by stellar feedback. This includes outflows and winds from newly formed stars, radiation from young clusters, and supernova explosions. High-resolution molecular line observations allow for the identification of individual star-forming regions and the study of their integrated properties. Moreover, simulations are now capable of accurately replicating the evolution of MCs including all key stellar feedback processes. We present 13CO(2-1) synthetic observations of the STARFORGE simulations produced using the radiative transfer code RADMC-3D, matching the observational setup of the SEDIGISM survey. From these, we identified the population of MCs using hierarchical clustering and analysed them to provide insights into the interpretation of observed MCs as they evolve. The flux distributions of the post-processed synthetic observations and the properties of the MCs, namely radius, mass, velocity dispersion, virial parameter and surface density, are consistent with those of SEDIGISM. Both samples of MCs occupy the same regions in the scaling relation plots; however, the average distributions of MCs at different evolutionary stages do not overlap on the plots. This highlights the reliability of our approach in modelling SEDIGISM and suggests that MCs at different evolutionary stages contribute to the scatter in observed scaling relations. We study the trends in MC properties over time to analyse their physical structure as they evolve. MCs appear as small, diffuse cloudlets in early stages, followed by their evolution to filamentary structures, before being shaped by stellar feedback into 3D bubbles and getting dispersed. These trends in the observable properties of MCs provide strong evidence that clouds exhibit distinct morphologies over the course of their evolution.
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All authors K.R. Neralwar, D. Colombo, S. Offner, A. Karska, M. Figueira, F. Wyrowski, S. Neupane, J.S. Urquhart, A. Duarte-Cabral

Astrophysics of Galaxies

Study of HI Turbulence in the SMC Using Multi-point Structure Functions

Bumhyun Lee, Min-Young Lee, Jungyeon Cho et al. (+19 more)

Turbulence in the interstellar medium (ISM) plays an important role in many physical processes, including forming stars and shaping complex ISM structures. In this work, we investigate the HI turbulent properties of the Small Magellanic Cloud (SMC) to reveal what physical mechanisms drive the turbulence and at what scales. Using the high-resolution HI data of the Galactic ASKAP (GASKAP) survey and multi-point structure functions (SF), we perform a statistical analysis of HI turbulence in 34 subregions of the SMC. Two-point SFs tend to show a linear trend, and their slope values are relatively uniform across the SMC, suggesting that large-scale structures exist and are dominant in the two-point SFs. On the other hand, seven-point SF enables us to probe small-scale turbulence by removing large-scale fluctuations, which is difficult to achieve with the two-point SFs. In the seven-point SFs, we find break features at scales of 34-84 pc, with a median scale of $\sim$50 pc. This result indicates the presence of small-scale turbulent fluctuations in the SMC and quantifies its scale. In addition, we find strong correlations between slope values of the seven-point SFs and the stellar feedback-related quantities (e.g., H$\alpha$ intensities, the number of young stellar objects, and the number of HI shells), suggesting that stellar feedback may affect the small-scale turbulent properties of the HI gas in the SMC. Lastly, estimated sonic Mach numbers across the SMC are subsonic, which is consistent with the fact that the HI gas of the SMC primarily consists of the warm neutral medium.
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All authors Bumhyun Lee, Min-Young Lee, Jungyeon Cho, Nickolas M. Pingel, Yik Ki Ma, Katie Jameson, James Dempsey, Helga Dénes, John M. Dickey, Christoph Federrath, Steven Gibson, Gilles Joncas, Ian Kemp, Shin-Jeong Kim, Callum Lynn, Antoine Marchal, N. M. McClure-Griffiths, Hiep Nguyen, Amit Seta, Juan D. Soler, Snežana Stanimirović, Jacco Th. van Loon

Astrophysics of Galaxies

The assembly of intermediate black holes with complementary approaches: Dragon II and BPop

Cristiano Ugolini

Intermediate-mass black holes (IMBHs) occupy the $ 10^2 - 10^5\,M_\odot $ range, but their existence remains poorly constrained. Only a few candidates have been suggested in dwarf galaxies, globular clusters, and LIGO-Virgo-Kagra detections. To investigate their formation and demographics, we adopt two complementary approaches. We first analyze the dragonii direct $N$-body simulations, which follow clusters with up to $ 10^6 $ stars, capture IMBHs growth. We then employ the semi-analytic code bpop, calibrated on dragonii, to explore a broad range of cluster and cosmological conditions. Our models reproduce merger rates consistent with GWTC-3, with $\sim30 - 60\%$ of BBHs forming dynamically, mainly in globular and nuclear clusters. About 2-3% of mergers involve an IMBH, producing intermediate-mass ratio inspirals. The IMBH mass distribution spans $2.5 \times 10^2 - 4 \times 10^4\,M_\odot $, with rare growth beyond $10^6\,M_\odot$. Formation efficiency rises with initial binary fraction but declines in metal-rich environments. IMBHs thus emerge as a distinct population bridging stellar and supermassive black holes.
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Astrophysics of Galaxies · Cross-listed from hep-ph

Probing Dark Matter Interactions with Stellar Motion near Sagittarius A*

R. Andrew Gustafson, Ian M. Shoemaker and Volodymyr Takhistov

Stars orbiting Sgr A* at the Milky Way's center provide a unique laboratory to test gravity and dark matter (DM). We demonstrate that DM interactions in stellar interiors induce a novel momentum transfer force, altering orbits beyond gravitational effects. Using S2's 2000-2019 orbital data we derive the first astrophysical constraints on DM-nucleon scattering, excluding new sub-GeV parameter space. Stellar lifetime constraints over Myr timescales complement these, surpassing some direct detection and cosmological limits. This establishes stellar dynamics as a novel probe of DM interactions.
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Astrophysics of Galaxies

An extended and extremely thin gravitational arc from a lensed compact symmetric object at redshift 2.059

J. P. McKean, C. Spingola, D. M. Powell et al. (+1 more)

Compact symmetric objects (CSOs) are thought to be short-lived radio sources with two lobes of emission that are separated by less than a kpc in projection. However, studies of such systems at high redshift is challenging due to the limited resolution of present-day telescopes, and can be biased to the most luminous objects. Here we report imaging of a gravitationally lensed CSO at a redshift of 2.059 using very long baseline interferometry at 1.7 GHz. The data are imaged using Bayesian forward modelling deconvolution, which reveals a spectacularly extended and thin gravitational arc, and several resolved features within the lensed images. The surface brightness of the lensing-corrected source shows two mini-lobes separated by 642 pc in projection, with evidence of multiple hotspots that have brightness temperatures of 10^8.6 to 10^9.2 K, and a total luminosity density of 10^26.3 W / Hz. By combining the well-resolved radio source morphology with previous multi-wavelength studies, we conclude that this object is likely a CSO of type 2, and that the properties are consistent with the bow-shock model for compact radio sources. Our analysis highlights the importance of combining high quality data sets with sophisticated imaging and modelling algorithms for studying the high redshift Universe.
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All authors J. P. McKean, C. Spingola, D. M. Powell, S. Vegetti

Cosmology and Nongalactic Astrophysics

A million-solar-mass object detected at cosmological distance using gravitational imaging

D. M. Powell, J. P. McKean, S. Vegetti et al. (+3 more)

Structure on sub-galactic scales provides important tests of galaxy formation models and the nature of dark matter. However, such objects are typically too faint to provide robust mass constraints. Here, we report the discovery of an extremely low-mass object detected via its gravitational perturbation to a thin lensed arc observed with milli-arcsecond-resolution very long baseline interferometry (VLBI). The object was identified using a non-parametric gravitational imaging technique and confirmed using independent parametric modelling. It contains a mass of $m_{\rm 80}=(1.13 \pm 0.04)\times 10^6{M_\odot}$ within a projected radius of 80 parsecs at an assumed redshift of 0.881. This detection is extremely robust and precise, with a statistical significance of 26$\sigma$, a 3.3 per cent fractional uncertainty on $m_{\rm 80}$, and an astrometric uncertainty of 194 $\mu$as. This is the lowest-mass object known to us, by two orders of magnitude, to be detected at a cosmological distance by its gravitational effect. This work demonstrates the observational feasibility of using gravitational imaging to probe the million-solar-mass regime far beyond our local Universe.
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All authors D. M. Powell, J. P. McKean, S. Vegetti, C. Spingola, S. D. M. White, C. D. Fassnacht

Earth and Planetary Astrophysics

Thin H$_2$-dominated Atmospheres as Signposts of Magmatic Outgassing on Tidally-Heated Terrestrial Exoplanets

R. Arora, S. Ranjan, P. Moitra et al. (+1 more)

H$_2$-dominated terrestrial exoplanets are highly accessible to atmospheric characterization via transmission spectroscopy, but such atmospheres are generally thought to be unstable to escape. Here, we propose that close-in, eccentric terrestrial exoplanets can sustain H$_2$-dominated atmospheres due to intense tidally-driven volcanic degassing. We develop an interior-atmosphere framework to assess whether volcanic outgassing can sustain \ch{H2}-dominated atmospheres over geologic timescales ($\geq$1 Gyr). We incorporate interior redox state, tidal heating, volatile inventory, and planetary parameters to compute outgassing fluxes and confront them with energy-limited hydrodynamic escape. We demonstrate that to sustain an H$_2$-dominated atmosphere, a terrestrial exoplanet must have a water-rich basal magma ocean and reduced melts, in addition to high eccentricity. We additionally demonstrate that detection of a specifically thin H$_2$-dominated atmosphere is a sign of current magmatic outgassing. We delineate an "outgassing zone" (OZ) most favorable to the existence of such planets, and identify the most observationally compelling targets. We propose combining precise mass-radius-eccentricity measurements with JWST constraints on atmospheric mean molecular mass $\mu$ to search for thin H$_2$-dominated atmospheres. Inversely, we argue that robust atmospheric non-detections on OZ exoplanets can constrain the planetary interior, including melt redox state, mantle melt fraction and volatile inventory, and tidal heat flux.
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All authors R. Arora, S. Ranjan, P. Moitra, A. Mallik

Astrophysics of Galaxies

The $M_{\rm BH}-M_{*}$ Relationship at $3<z<7$: Big Black Holes in Little Red Dots

Brenda L. Jones, Dale D. Kocevski, Fabio Pacucci et al. (+25 more)

JWST has identified a large population of faint, broad-line active galactic nuclei (AGN) in the early universe that are powered by black holes (BHs) that often appear overmassive relative to their host galaxies. In this study, we examine the relationship between BH mass and galaxy stellar mass at $3<z<7$ using a sample of 70 broad-line AGN identified using NIRSpec/G395M spectroscopy from the CEERS, JADES, and RUBIES surveys. Roughly half (43%) of our sample appear heavily reddened and are classified as little red dots (LRDs). We estimate BH masses ($M_{\rm BH}$) using single-epoch virial techniques, while host stellar masses ($M_{\star}$) are inferred using a combination of two-dimensional surface brightness profile fitting and spectral energy distribution modeling. We find that a majority of our sources (50/70) have $M_{\rm BH}/M_{\star}$ ratios that are 1-2 dex higher than that observed in AGN locally. Using a forward-modeling Bayesian framework that accounts for uncertainties, intrinsic scatter, and selection effects, we infer a $M_{\rm BH}-M_{\star}$ relationship that is $>3\sigma$ above the relationship measured for local broad-line AGN. We derive an intrinsic scatter in this relationship of $0.9$ dex, which does not vary over the redshift range of our sample. We also find that the $M_{\rm BH}/M_{\star}$ ratio increases by $2.3$ dex from $z = 3.5$ and $z = 6.5$ with a confidence level of $ > 3\sigma$. We attribute this trend with the increasing fraction of LRDs in our sample at $z>4$ as their host masses are $\sim1$ dex lower than the non-LRD AGN in our sample. These results support a picture in which the BHs powering JWST's broad-line AGN are genuinely overmassive and become increasingly so with redshift. We discuss the implications of our findings on early BH growth relative to that of their host galaxies and the constraints it places on BH seeding models.
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All authors Brenda L. Jones, Dale D. Kocevski, Fabio Pacucci, Anthony J. Taylor, Steven L. Finkelstein, Johannes Buchner, Jonathan R. Trump, Rachel S. Somerville, Michaela Hirschmann, L. Y. Aaron Yung, Guillermo Barro, Eric F. Bell, Laura Bisigello, Antonello Calabro, Nikko J. Cleri, Avishai Dekel, Mark Dickinson, Giovanni Gandolfi, Mauro Giavalisco, Norman A. Grogin, Kohei Inayoshi, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Lorenzo Napolitano, Masafusa Onoue, Swara Ravindranath, Giulia Rodighiero, Stephen M. Wilkins

Cosmology and Nongalactic Astrophysics

Control variates from Eulerian and Lagrangian perturbation theory: Application to the bispectrum

Nickolas Kokron and Shi-Fan Chen

Control variates have seen recent interest as a powerful technique to reduce the variance of summary statistics measured from costly cosmological $N$-body simulations. Of particular interest are the class of control variates which are analytically calculable, such as the recently introduced 'Zeldovich control variates' for the power spectrum of matter and biased tracers. In this work we present the construction of perturbative control variates in Eulerian and Lagrangian perturbation theory, and adopt the matter bispectrum as a case study. Eulerian control variates are analytically tractable for all $n$-point functions, but we show that their correlation with the $N$-body $n$-point function decays at a rate proportional to the sum-of-squared wavenumbers, hampering their utility. We show that the Zeldovich approximation, while possessing an analytically calculable bispectrum, is less correlated at low-$k$ than its Eulerian counterpart. We introduce an alternative – the 'shifted control variate' – which can be constructed to have the correct tree-level $n$-point function, is Zeldovich-resummed, and in principle has an analytically tractable bispectrum. We find that applying this shifted control variate to the $z=0.5$ matter bispectrum is equivalent to averaging over $10^4$ simulations for the lowest-$k$ triangles considered. With a single $V=1({\rm Gpc}/h)^3$ $N$-body simulation, for a binning scheme with $N\approx 1400$ triangles from $k_{\rm min} = 0.04 h {\rm Mpc}^{-1}$ to $k_{\rm \max} = 0.47 h {\rm Mpc}^{-1}$, we obtain sub-2% precision for every triangle configuration measured. This work enables the development of accurate bispectrum emulators – a probe of cosmology well-suited to simulation-based modeling – and lays the theoretical groundwork to extend control variates for the entire $n$-point hierarchy.
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Cosmology and Nongalactic Astrophysics

Stacking 21-cm Maps around Lyman-$\alpha$ Emitters during Reionization: Prospects for a Cross-correlation Detection with the Hydrogen Epoch of Reionization Array

Kai-Feng Chen, Meredith Neyer, Jacqueline N. Hewitt et al. (+2 more)

Observations of the redshifted 21-cm line during the Epoch of Reionization will open a new window to probe the intergalactic medium during the formation of the first stars, galaxies, and black holes. A particularly promising route to an initial detection is to cross-correlate tomographic 21-cm maps with spectroscopically confirmed Lyman-$\alpha$ emitters (LAEs). High-redshift LAEs preferentially reside in ionized bubbles that are strongly anticorrelated with the surrounding neutral regions traced by 21-cm observations. In this work, we study the prospect of detecting such a cross-correlation signal by stacking 21-cm image cubes around LAEs using a current-generation 21-cm instrument – the Hydrogen Epoch of Reionization Array (HERA). Our forecast adopts a realistic mapping pipeline to generate foreground-free 21-cm image cubes. The statistical properties of these images, arising from the complex instrumental response, are carefully accounted for. We further introduce a physically motivated signal template calibrated on the THESAN radiation-hydrodynamic simulations, which connects the cross-correlation amplitude to the global neutral fraction. Our results show that a sample of ~50 spectroscopically confirmed LAEs is sufficient to begin constraining the reionization history. These results represent an important preparatory step toward joint analyses of 21-cm experiments with upcoming wide-area, high-redshift galaxy surveys from Euclid and the Nancy Grace Roman Space Telescope.
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All authors Kai-Feng Chen, Meredith Neyer, Jacqueline N. Hewitt, Aaron Smith, Mark Vogelsberger

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Axion Perturbations: A General Analytical Treatment

Itamar J. Allali, Priyesh Chakraborty, JiJi Fan et al. (+1 more)

Cosmological data provides us two key constraints on dark matter (DM): it must have a particular abundance, and it must have an adiabatic spectrum of density perturbations in the early universe. Many different cosmological scenarios have been proposed that establish the abundance of axion DM in qualitatively different ways. In this paper we emphasize that, despite this variety of backgrounds, the perturbations in axion DM can be understood from universal principles. How does a feebly interacting axion field acquire perturbations proportional to those of photons? How do the isocurvature power spectrum and non-Gaussianity depend on the background evolution of the universe? We answer these questions for a completely general choice of cosmological background and temperature-dependent axion potential. We show that the most general solution to the axion field equation on super-horizon scales is entirely determined by the family of background solutions for different initial field values $\theta_{\rm ini}$. This holds for both the component in the field perturbation solution contributing to the DM isocurvature perturbation (enhanced at late times by the sensitivity of the DM abundance to the initial condition, $\partial \Omega_a / \partial \theta_{\rm ini}$, which can be large for initial conditions near the hilltop), and the other component that contributes to the DM curvature perturbation. In particular, we explain that an unperturbed axion field in the early universe evolving into one with nontrivial adiabatic perturbations is guaranteed by Weinberg's theorem on adiabatic modes. These results have been derived before with various assumptions, such as a radiation dominated background or a quadratic potential. Our aim is to give a clear, simple derivation that is manifestly independent of those assumptions, and thus can be applied to any cosmological axion scenario.
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All authors Itamar J. Allali, Priyesh Chakraborty, JiJi Fan, Matthew Reece

Instrumentation and Methods for Astrophysics

Photometric Redshift Estimation for Rubin Observatory Data Preview 1 with Redshift Assessment Infrastructure Layers (RAIL)

T. Zhang, E. Charles, J.F. Crenshaw et al. (+87 more)

We present the first systematic analysis of photometric redshifts (photo-z) estimated from the Rubin Observatory Data Preview 1 (DP1) data taken with the Legacy Survey of Space and Time (LSST) Commissioning Camera. Employing the Redshift Assessment Infrastructure Layers (RAIL) framework, we apply eight photo-z algorithms to the DP1 photometry, using deep ugrizy coverage in the Extended Chandra Deep Field South (ECDFS) field and griz data in the Rubin_SV_38_7 field. In the ECDFS field, we construct a reference catalog from spectroscopic redshift (spec-z), grism redshift (grism-z), and multiband photo-z for training and validating photo-z. Performance metrics of the photo-z are evaluated using spec-zs from ECDFS and Dark Energy Spectroscopic Instrument Data Release 1 samples. Across the algorithms, we achieve per-galaxy photo-z scatter of $\sigma_{\rm NMAD} \sim 0.03$ and outlier fractions around 10% in the 6-band data, with performance degrading at faint magnitudes and z>1.2. The overall bias and scatter of our machine-learning based photo-zs satisfy the LSST Y1 requirement. We also use our photo-z to infer the ensemble redshift distribution n(z). We study the photo-z improvement by including near-infrared photometry from the Euclid mission, and find that Euclid photometry improves photo-z at z>1.2. Our results validate the RAIL pipeline for Rubin photo-z production and demonstrate promising initial performance.
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All authors T. Zhang, E. Charles, J.F. Crenshaw, S.J. Schmidt, P. Adari, J. Gschwend, S. Mau, B. Andrews, E. Aubourg, Y. Bains, K. Bechtol, A. Boucaud, D. Boutigny, P. Burchat, J. Chevalier, J. Chiang, H.-F. Chiang, D. Clowe, J. Cohen-Tanugi, C. Combet, A. Connolly, S. Dagoret-Campagne, P.N. Daly, F. Daruich, G. Daubard, J. De Vicente, H. Drass, K. Fanning, E. Gawiser, M. Graham, L.P. Guy, Q. Hang, P. Ingraham, O. Ilbert, M. Jarvis, M.J. Jee, T. Jenness, A. Johnson, C. Juramy-Gilles, S.M. Kahn, J.B. Kalmbach, Y. Kang, A. Kannawadi, L.S. Kelvin, S. Liang, O. Lynn, N.B. Lust, M. Lutfi, A. Malz, R. Mandelbaum, S. Marshall, J. Meyers, M. Migliore, M. Moniez, J. Neveu, J.A. Newman, E. Nourbakhsh, D. Oldag, H. Park, S. Pelesky, A.A. Plazas Malagón, B. Quint, M. Rahman, A. Rasmussen, K. Reil, W. Roby, A. Roodman, C. Roucelle, M. Salvato, B. Sánchez, D. Sanmartim, R.H. Schindler, J. Scora, J. Sebag, N. Sedaghat, I. Sevilla-Noarbe, R. Shirley, A. Shugart, R. Solomon, D. Taranu, G. Thayer, L. Toribio San Cipriano, E. Urbach, Y. Utsumi, W. van Reeven, A. von der Linden, C.W. Walter, W.M. Wood-Vasey, J. Zuntz, LSST Dark Energy Science Collaboration

Astrophysics of Galaxies

$\texttt{geko}$: A tool for modelling galaxy kinematics and morphology in JWST/NIRCam slitless spectroscopic observations

A. Lola Danhaive and Sandro Tacchella

Wide-field slitless spectroscopy (WFSS) is a powerful tool for studying large samples of galaxies across cosmic times. With the arrival of JWST, and its NIRCAM grism mode, slitless spectroscopy can reach a medium spectral resolution of $(R\sim 1600)$, allowing it to spatially resolve the ionised-gas kinematics out to $z\sim 9$. However, the kinematic information is convolved with morphology along the dispersion axis, a degeneracy that must be modelled to recover intrinsic properties. We present the Grism Emission-line Kinematics tOol ($\texttt{geko}$), a Python package that forward-models NIRCam grism observations and infers emission-line morphologies and kinematics within a Bayesian framework. $\texttt{geko}$ combines Sérsic surface-brightness models with arctangent rotation curves, includes full point-spread function (PSF) and line-spread function (LSF) convolution, and leverages gradient-based sampling via $\texttt{jax}$/$\texttt{numpyro}$ for efficient inference. It recovers parameters such as effective radius, velocity dispersion, rotational velocity, rotational support, and dynamical mass, with typical run times of $\sim$20 minutes per galaxy on GPUs. We validate performance using extensive mock data spanning position angle, S/N, and morphology, quantifying where degeneracies limit recovery. Finally, we demonstrate applications to real FRESCO H$\alpha$ emitters at $z\approx 4-6$, recovering both rotation- and dispersion-dominated systems. $\texttt{geko}$ opens the way to statistical studies of galaxy dynamics in the early Universe and is publicly available at https://github.com/angelicalola-danhaive/geko.
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