Astrophysics of Galaxies
The Impact of Simulation Resolution on Dwarf Galaxy Stellar Stream Populations in FIRE
Yasmine J. Meziani, Nondh Panithanpaisal, Robyn E. Sanderson et al. (+4 more)
Cosmological simulations allow us to study
galaxy-progenitor stream populations, allowing comparisons with observations to constrain
galaxy formation physics. Previous work found that present-day
galaxy-progenitor streams in FIRE have larger pericenters than observed in the MW, which might indicate that they tidally disrupt at larger distances, where the Galactic tides are weaker, than in the MW. One possible explanation is that they tidally disrupt too quickly because of limited resolution. At lower resolution, low-mass dwarf
galaxies can be puffier and more susceptible to disruption. We build and compare dwarf-
galaxy stream catalogs in two FIRE-2 cosmological zoom-in simulations with identical initial conditions (m12i) but different particle mass resolution (7070 $M_\odot$ and 880 $M_\odot$). The higher-resolution run yields a larger dwarf
galaxy stream population (22 streams versus 14) using the same cutoff of 100
star particles, primarily because it resolves lower-mass streams (down to $\sim10^{5}$ $M_\odot$). Both simulations form streams at galactocentric radii < 50 kpc, but the higher-resolution Triple Latte simulation produces more streams at these small radii. We find that dwarf
galaxies in the higher-resolution simulation begin disrupting at smaller pericenters than in the lower-resolution simulation. By cross-matching stream candidates, we identify counterparts for $\sim$89$\%$ of the systems in the lower-resolution simulation. For matched systems that remain on similar orbits, the higher-resolution counterparts remain intact for longer. The orbital properties of streams in the higher-resolution simulation are broadly consistent with the MW dwarf-
galaxy stream population, in contrast to the lower-resolution simulation.
Read the full abstract ▾
All authors Yasmine J. Meziani, Nondh Panithanpaisal, Robyn E. Sanderson, Andrew Wetzel, Pratik J. Gandhi, Philip F. Hopkins, Adriana Dropulic
Astrophysics of Galaxies
Star Formation Mitosis: The Effects of Particle Splitting on the Star Formation Outcome
Shivan Khullar, Michael Y. Grudić, Christopher D. Matzner et al. (+3 more)
Particle splitting can increase the dynamic range in Lagrangian astrophysical simulations by several orders of magnitude. However, such methods can introduce numerical noise that may affect the rate of convergence, particularly for collapse problems where fragmentation could be artificially suppressed or enhanced. Thus it is necessary to determine how these errors propagate to key quantities of interest, and to correct or mitigate them where possible. Using GIZMO's MFM-MHD method, we perform a set of $\approx 220$ simulations of a uniform-density turbulent gas sphere undergoing collapse, systematically varying the cloud mass and radius, feedback physics, initial resolution, the pace and cadence at which we split particles and the sink (accreting) or single-age stellar population (SSP; non-accreting) particle formation prescription. Crucially, we compare with control runs that start with uniformly-high resolution without splitting. While we find no evidence for artificial fragmentation caused by splitting particles, particle splitting runs have a smoother density field than their non-splitting counterparts. Due to this, particle splitting runs exhibit minor differences in the density and
turbulence statistics. However, they form about the same total stellar mass as the control non-splitting runs, albeit with a slightly different mass spectrum. As a result, particle splitting runs have a different evolutionary history, compared to runs without particle splitting, especially when stellar feedback is present. Despite the changes seen in runs where we split particles, the numerical solution lies within the scatter inherently present in these chaotic systems, which we model by modifying the initial turbulent velocity field. Our results here argue that particle splitting generally “works" for
star formation applications, despite some systematic differences in the specifics.
Read the full abstract ▾
All authors Shivan Khullar, Michael Y. Grudić, Christopher D. Matzner, Philip F. Hopkins, Norman Murray, Claude-André Faucher-Giguère
Astrophysics of Galaxies
The star formation history of Orion is structured and episodic
Alena Rottensteiner, João Alves, Stefan Meingast et al. (+6 more)
The propagation of
star formation throughout a molecular cloud complex can tell us much about its physical drivers and the importance of environmental versus intrinsic processes. We reconstruct the
star formation history (SFH) of the Orion
star-forming complex using the highest-resolution age map currently available. It comprises 47 co-spatial and co-moving groups identified by the SigMA clustering
algorithm, with homogeneously derived ages and group memberships. We find four periods of increased
star formation, separated by ~5 Myr each. The two periods of highest increase, at 6.4 and 11.3 Myr, can be statistically localized, together hold ca. 59% of all
stars, and are robust against resampling and changes to the age fitting. The two older, smaller increases at 16.2 and 21.4 Myr can be identified in the age distribution, but cannot be shown to be robust at this point. The ~5 Myr spacing between the episodes of increased
star formation is the same as found for the nearby Scorpius-Centaurus (Sco-Cen)
star-forming region. We find no methodological bias that could produce the SFH structure. We identify spatio-temporally connected structures, including three cluster-chain candidates. We conclude that
star formation in Orion seems to occur on the same timescales but with a different pattern than in Sco-Cen. The cause of the ~5 Myr separations remains a mystery, and its detection in two distinct
star-forming regions needs further investigation.
Read the full abstract ▾
All authors Alena Rottensteiner, João Alves, Stefan Meingast, Sebastian Hutschenreuter, Núria Miret-Roig, Josefa Großschedl, Cameren Swiggum, Sebastian Ratzenböck, Monika G. Petr-Gotzens
Astrophysics of Galaxies
The impact of relativistic AGN jets on realistic galaxy cluster environments
K. Hervella-Seoane, M. Perucho, S. Planelles et al. (+2 more)
Context. Low-power FRI-like
radio jets dominate the AGN population, yet the main mechanism of heating the intracluster medium (ICM) and its efficiency remain a matter of debate. Aims. We investigate the impact of intermediate-power FRI-like relativistic jets on the inner region of realistic ICM, focusing on the role of weak shocks on heating and the environmental coupling in regulating energy deposition. Methods. We present six three-dimensional relativistic-hydrodynamic simulations of (1e44 - 1e45) erg/s FRI-like jets propagating through the central regions of realistic ICM environments extracted from cosmological GADGET-3 runs. Each simulation tracks 20 Myr of continuous jet activity with radiative cooling included. Results. Despite their intermediate power and mildly relativistic speed at injection, they decelerate rapidly to trans-sonic velocities (average Mach numbers ~ 2.3) and generate weak bow shocks that dominate the energy transfer. Approximately, 80% of the injected kinetic power is converted into internal energy of the ambient ICM, and bremsstrahlung cooling noticeably reduces the temperature of the shocked shells as they expand. Conclusions. Our results demonstrate that heating of the intergalactic and intracluster medium is highly efficient even in the case of weak shocks in FRI-like sources. This finding suggests low-power jets are a viable solution to the long-standing cooling-flow problem and likely regulate
star formation across diverse
galaxy cluster environments.
Read the full abstract ▾
All authors K. Hervella-Seoane, M. Perucho, S. Planelles, J.M. Martí, V. Quilis
Astrophysics of Galaxies
LIGHTS. Limitations of Far-Infrared Tracers for Galactic Cirrus Mitigation in the Era of Ultra-Deep Imaging
Ouldouz Kaboud, Ignacio Trujillo, Ignacio Ruiz Cejudo et al. (+18 more)
Current and forthcoming deep optical imaging surveys are reaching surface brightness levels fainter than 30 mag/arcsec$^2$, where Galactic cirrus emission becomes a significant contaminant. This poses a major challenge for the study of extremely low-surface-brightness extragalactic structures. We investigate the relationship between far-infrared emission, as traced by the Herschel 250 $\mu$m band, and optical surface brightness in the Sloan g- and r-bands. We find that, for Galactic cirrus with $\mu_g\gtrsim$~27 mag/arcsec$^2$, a linear relation is consistent with the data, assuming optically thin dust, with optical cirrus emission amounting to $\sim$0.1% of the far-infrared flux. Using Herschel far-infrared data to trace Galactic cirrus enables its identification over wide areas, but at the cost of significantly reducing spatial resolution. This limitation introduces source confusion and restricts the effective surface brightness depth that can be robustly probed in optical data. We show that, when cirrus emission is modeled using Herschel 250 $\mu$m data, the limiting surface brightness is $\mu_V\sim$~28 mag/arcsec$^2$, substantially shallower than the nominal depth of surveys such as LIGHTS or the 10-year coadd LSST ($\mu_V\sim$~30.5 mag/arcsec$^2$). These results highlight a fundamental limitation in the use of currently available far-infrared data for cirrus mitigation in ultra-deep optical imaging, and emphasize the need for higher-resolution cirrus tracers to fully exploit the depth of upcoming surveys.
Read the full abstract ▾
All authors Ouldouz Kaboud, Ignacio Trujillo, Ignacio Ruiz Cejudo, S. Zahra Hosseini-ShahiSavandi, Mireia Montes, Sergio Guerra Arencibia, Mauro D'Onofrio, Dennis Zaritsky, Javier Roman, Nushkia Chamba, Giulia Golini, Chen-Yu Chuang, Minh Ngoc Le, Carlos Marrero-de la Rosa, Zahra Sharbaf, Richard Donnerstein, Sepideh Eskandarlou, Raul Infante-Sainz, Garreth Martin, Samane Raji, Nafise Sedighi
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
XClass: An Automated Multiwavelength Machine-Learning Pipeline for Classification of Extragalactic X-ray Sources. I. Pipeline Description
Blagoy Rangelov, Nicholas Moore, Haley Dutton et al. (+1 more)
Most X-ray sources detected in nearby
galaxies by the Chandra X-ray Observatory lack astrophysical classifications. We present XClass (X-ray Classifier for extragalactic sources), an end-to-end machine-learning pipeline that classifies extragalactic X-ray point sources into seven classes: AGN, LMXBs, HMXBs, CVs, low-mass and high-mass foreground
stars, and
supernova remnants. The key challenge is photometric heterogeneity: training sources are predominantly Galactic with photometry from wide-field surveys (PanSTARRS and 2MASS), while extragalactic targets require Hubble Space
Telescope (HST) imaging in a disjoint filter system. We address this through a spectral energy distribution (SED) translation that fits class-appropriate spectral models to each training source and convolves the best-fit model through HST filter curves, producing synthetic magnitudes in a common feature space. The classifier uses an asymmetric two-stage Random Forest: Stage 1 separates broad categories (AGN, X-ray binaries, SNRs,
stars) and Stage 2 resolves X-ray binaries into LMXBs and HMXBs using an augmented feature vector that includes Stage 1 probabilities. The training set is assembled from ten Galactic catalogs and extragalactic SNR catalogs, cross-matched with the Chandra Source Catalog v2.1. Features include X-ray hardness ratios, SED-translated HST colors, and X-ray-to-optical flux ratios. We restrict the training set to sources with at least one optical magnitude, avoiding imputation artifacts; the pipeline achieves 99.6% accuracy and balanced accuracy of 0.90 on the resulting 11,374-source optical baseline, with excellent calibration (ECE = 0.002). XClass is modular, generalizable to any HST filter configuration, and will be applied to M31 and M33 in a companion paper.
Read the full abstract ▾
All authors Blagoy Rangelov, Nicholas Moore, Haley Dutton, Erika Marentes
Astrophysics of Galaxies
Which Milky Way Streams Make the Best Dark Matter Detectors?
Vedant Chandra, Charlie Conroy, Risa Wechsler et al. (+7 more)
The abundance and properties of low-mass dark matter subhalos can be inferred by measuring the density and velocity structure of stellar streams, testing physical models of dark matter. Which streams make the most promising dark matter detectors, and which subhalos would they encounter? We use the semi-analytic model galacticus to simulate the Milky Way's dark subhalos, including tidal stripping under the influence of the galactic disk. Deriving stream initial conditions that best match present-day observations, we forecast subhalo encounters for 24 globular cluster streams around the Milky Way. Over their lifetimes, the 10 most perturbed streams are predicted to each experience $\approx 2$-$12$ significant subhalo encounters with velocity kicks $v_\mathrm{kick} > 0.1$ km s$^{-1}$. Jet, AAU, GD-1, and Palomar 5 lead the list, with Jet encountering twice the subhalos of any other stream. The subhalos that encounter streams have been tidally stripped to $1$-$20\%$ of their peak mass and are twice as compact as previous works have assumed. A spectroscopic survey of streams with sub-km s$^{-1}$ precision could reveal the influence of dark subhalos below the threshold of
galaxy formation. Predicting the abundance and scatter of low-mass subhalos that reach the inner
galaxy remains a dominant uncertainty in connecting stellar streams to models of dark matter.
Read the full abstract ▾
All authors Vedant Chandra, Charlie Conroy, Risa Wechsler, Ana Bonaca, Andrew Benson, Jacob Nibauer, Tara Dacunha, Philip Mansfield, Paul Menker, Anya Phillips
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
Gaia neutron stars: demographics, birth rates, and connections to other neutron star populations
Cheyanne Shariat, Natsuko Yamaguchi, Kareem El-Badry et al. (+1 more)
Gaia DR3 revealed a new class of
neutron stars (NSs) in au-scale orbits with solar-type companions. How these 'Gaia NSs' form remains unclear, and constraining their intrinsic population properties is a necessary step toward understanding their origin. However, the current sample of 27 Gaia NS candidates is strongly biased by Gaia's astrometric sensitivity. In this work, we carefully model the Gaia selection function and incorporate it into a hierarchical
Bayesian framework to infer the intrinsic demographics of the Gaia NS population. We find that the population favors a decreasing period distribution with power-law slope $\alpha_P=-0.75 \pm 0.35$, a visible-
star mass distribution peaked near $M_1\approx 0.85~{\rm M_\odot}$ ($\sigma_{M_1} \approx 0.2~{\rm M_\odot}$), an NS mass distribution peaked near $M_{\rm NS}\approx 1.3~{\rm M_\odot}$ with a tail towards higher masses, and an eccentricity distribution weighted toward moderate-to-large eccentricities. The intrinsic space density is $n\approx120~{\rm kpc^{-3}}$ within 2 kpc, implying that only $\sim3\%$ of the local Gaia NS population has been discovered so far. Our forecasts predict that Gaia DR4 will increase the sample to $\sim300$-650 NS candidates, including access to longer orbital periods that will provide direct tests of formation models. Finally, we place Gaia NSs in the context of the broader Galactic NS population by comparing their intrinsic birth rate, lifetime, and size to other classes of isolated and binary NSs. Only 0.01% - 1% of all NSs are born into au-scale orbits with solar-type companions, making the birth rate of Gaia NSs 10 - 100 times smaller than that of high-mass X-ray binaries and broadly comparable to symbiotic X-ray binaries.
Read the full abstract ▾
All authors Cheyanne Shariat, Natsuko Yamaguchi, Kareem El-Badry, Thomas J. Maccarone
Astrophysics of Galaxies
Water enhances the formation of refractory sulfur in interstellar ices
Carlos del Burgo Olivares, Hector Carrascosa, Guillermo M. Muñoz Caro et al. (+3 more)
Sulfur is the tenth most abundant element in space, yet it is strongly depleted in the gas phase of dense interstellar regions, suggesting sequestration in dust grain components that are difficult to detect. We study whether UV irradiation and thermal processing of H2S-containing interstellar-ice analogues can produce refractory sulfur species, and whether water-dominated ice enhances their formation. We performed UV irradiation and warm-up experiments on H2S-containing ice analogues with and without water, and the resulting refractory residues were analysed ex situ. Refractory sulfur species, including the sulfur allotropes S6-S8, are formed during UV irradiation and thermal processing of H2S-containing interstellar-ice analogues. Water enhances the formation of these sulfur allotropes by two orders of magnitude. We propose a formation mechanism in which ionic intermediates stabilised by the water-ice
matrix promote chain growth and cyclisation, yielding predominantly S8. The combined detection in our residues of sulfur allotropes and polythionic species, also reported in meteorites and samples returned from asteroids, supports their formation in pre-cometary ice mantles covering dust grains. Because these species can incorporate multiple sulfur atoms per molecule, they constitute an efficient solid-phase reservoir for the missing sulfur in dense cloud environments where young
stars are born. Refractory sulfur can therefore serve as a tracer of water-ice environments in space.
Read the full abstract ▾
All authors Carlos del Burgo Olivares, Hector Carrascosa, Guillermo M. Muñoz Caro, Rafael Lebron-Aguilar, Jose E. Quintanilla-Lopez, Yao-Jen Chen
Astrophysics of Galaxies
Probing the Reionization History and Bubble Sizes with JWST Lyman-$\alpha$ Fraction Measurements
Aritra Kundu, Adam Lidz and Guochao Sun
Recent James Webb Space
Telescope (JWST) measurements quantify the fraction of ultraviolet-selected
galaxies showing detectable Lyman-alpha (Ly-$\alpha$) lines at $z \sim 6-14$. These Ly-$\alpha$ fractions are partly shaped by Ly-$\alpha$ scattering from neutral hydrogen in the surrounding intergalactic medium (IGM), and so the observed Ly-$\alpha$ fraction
evolution can inform our understanding of the reionization history and the size distribution of ionized bubbles during reionization. We compare the JWST measurements with Ly-$\alpha$ transmission calculations based on both the THESAN reionization simulations and a flexible semi-analytic model. In each case, we calibrate a sub-grid model for the intrinsic Ly-$\alpha$ emission lines emerging from the interstellar medium (ISM) and circumgalactic medium (CGM) of the host
galaxies using empirical estimates of the Ly-$\alpha$ equivalent width (EW) distributions at $z \sim 6$. We find that the reionization history and bubble sizes in THESAN yield good agreement with current JWST Ly-$\alpha$ fraction observations, with a reduced $\chi^2_\nu = 0.4-1.2$. Our semi-analytic models and THESAN Ly-$\alpha$ transmission calculations agree well, allowing us to explore a wide range of reionization models. We derive $1\sigma$ bounds on the average mass-weighted neutral fractions of: $\langle x_{\mathrm{HI}} \rangle$ = $0.38^{+0.14}_{-0.38}$ ($0.52^{+0.09}_{-0.21}$), $0.57^{+0.23}_{-0.57}$ ($0.68^{+0.12}_{-0.39}$), and $0.93^{+0.05}_{-0.17}$ ($0.89^{+0.11}_{-0.15}$) at $z \sim$ 7, 8, and 11, based on the Ly-$\alpha$ fraction measurements with EW $>25\,\mathring{\rm A}$ ($>10\,\mathring{\rm A}$).
Read the full abstract ▾
Astrophysics of Galaxies
Sub-kiloparsec Test of the Kennicutt-Schmidt Relation in a Strongly Lensed Dusty Star-Forming Galaxy at z~2.78
C. Cornil-Baïotto, J. Molina, G. Mahler et al. (+9 more)
[abridged]
Star formation is a key process driving
galaxy evolution, but understanding how it proceeds within the interstellar medium (ISM) requires resolving cold molecular gas and dust on sub-kpc scales. At z~2-3, near the peak of
cosmic star formation, such resolution can generally only be achieved through strong gravitational
lensing. We present an ALMA study of SMMJ0658, a 20x-magnified main-sequence
star-forming
galaxy at z=2.7768 +/- 0.0002, lensed by the Bullet Cluster (z=0.296) into three images. We use 0.2" and 0.6" ALMA Band-3 observations to test the Kennicutt-Schmidt (KS) relation at sub-kpc scales at
cosmic noon. Using a JWST-based strong-
lensing model of the Bullet Cluster, we reconstruct source-plane CO(3-2) and rest-frame 803um dust-continuum maps down to ~200pc scales. We derive spatially resolved molecular gas and
star formation rate surface densities, depletion times, and the scale dependence of the CO-to-dust flux ratio over 200pc-3.2kpc apertures. The 0.2" ALMA data reveal massive, dense
star-forming clumps, with Sigma_mol ~1.3-2.3 x 10^3 M_sun pc^-2, Sigma_SFR ~0.5-2.3 M_sun yr^-1 kpc^-2, and tau_dep ~0.82-2.56 Gyr. CO-dust spatial decorrelation produces a strong scale dependence in tau_dep. We find a KS-relation breakdown scale of 0.8 +/- 0.1 kpc, consistent with individual regions tracing distinct stages of the
star-formation cycle. The ALMA and JWST data also reveal evidence for a lensed
galaxy pair at z~2.78, although whether SMMJ0658 is undergoing an early-stage interaction remains uncertain. Our results show that the apparent universality of the KS relation breaks down once individual
star-forming regions are spatially resolved, in line with observations from the local universe to z~1. We extend this picture to z~2.78, providing new insight into the resolved properties of the clumpy cold ISM and the
star-formation cycle at
cosmic noon.
Read the full abstract ▾
All authors C. Cornil-Baïotto, J. Molina, G. Mahler, G. Rihtaršič, M. Boquien, M. Bradač, E. Ibar, A. H. Gonzalez, T. Verdugo, O. López-Cruz, J. Magaña, V. Motta
Astrophysics of Galaxies
The assembly history of NGC 1365 through chemical archaeology
Lisa J. Kewley, Kathryn Grasha, Alex Garcia et al. (+8 more)
Galaxies build through infalling gas and
galaxy mergers. Tracking the dynamical history of a
galaxy from a single snapshot in time is notoriously difficult. We show that the dynamical history of a
galaxy can be tracked using oxygen abundances as archeological tracers. We derive the gas-phase oxygen abundances for 4546 spaxels across the face-on spiral
galaxy NGC~1365 at a spatial resolution of 175 pc, providing one of the most detailed chemical fossil records of a spiral
galaxy outside our Milky Way. We apply IllustrisTNG cosmological simulations to analyse the chemical abundance distribution in a theoretical model for NGC~1365. In the model, the main disk oxygen abundance gradient formed earliest, 11.9-12.5 billion years ago via mergers with multiple dwarf
galaxies. A steep inner bar gradient formed slowly over the last 12 billion years through enrichment from
star formation triggered by the infall of gas into the nuclear regions. An extended ionized gas disk with flat oxygen abundances was assembled more recently (5.9-8.6 billion years ago) through a minor merger. This work indicates that cosmological simulations and ultra-high spatial resolution oxygen abundances together can provide an archaeological probe of the
star formation and merger histories of spiral
galaxies.
Read the full abstract ▾
All authors Lisa J. Kewley, Kathryn Grasha, Alex Garcia, Paul Torrey, Jeff Rich, Z. S. Hemler, Qian-hui Chen, Peixin Zhu, Mark Seibert, Lars Hernquist, Barry Madore
Astrophysics of Galaxies
When Streams Curve Away: a Test of Dark Matter from Extragalactic Stellar Stream Populations
Nathaniel Starkman, Jacob Nibauer, Sarah Pearson et al. (+2 more)
The nature of dark matter sets the shape of galactic
halos: collisionless cold dark matter (CDM) predicts triaxial
halos, while scattering in self-interacting dark matter (SIDM) rounds them toward sphericity. We show that a large catalog of projected stellar stream tracks can statistically constrain
halo shapes, and therefore the particle nature of dark matter, without detailed modeling of any individual stream or gravitational potential. We develop a new
geometric diagnostic for stellar streams: if the
curvature of any segment along a stream points away from the host
galaxy's projected center of mass, then that stream falsifies broad classes of potentials, including spherical ones. We call such a segment convex. The diagnostic needs only a projected stream track and a host-center estimate, requiring no kinematics, distances, progenitor model, or fit to individual host potentials.
Halo triaxiality sets the rate at which streams show convex segments, making this rate an observable of the
halo-shape distribution and the underlying dark-matter model. We forecast that upcoming survey-scale stream morphology catalogs can discriminate between CDM and SIDM at up to $5\sigma$.
Read the full abstract ▾
All authors Nathaniel Starkman, Jacob Nibauer, Sarah Pearson, Sirui Wu, Lina Necib
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
Tracing star formation across the Rosette nebula using deep Spitzer imaging
Daniel Capela, Aleks Scholz, Koraljka Muzic et al. (+4 more)
We present a deep large-scale infrared survey of young stellar objects in the Rosette Nebula. Our analysis is based on stacked archival Spitzer/IRAC images. The images have been treated with the software DeNeb to remove nebulous emission. Our catalogue contains ~20000 sources with photometry in all 4 IRAC bands from 3.6 to 8.0 microns, complemented with near-infrared and optical data. From this database, we identify YSOs using multi-filter colour-colour criteria. We select 1528 YSOs, from which 1303 are Class II and 225 are Class I. Using this sample, we compile a list of clusters and groups of YSOs in the Rosette region, including previously known ones, plus three newly identified groups. Using our census of YSOs, in combination with the literature, we derive the Class I ratios and disk fractions for clusters in the nebula. The main clusters in the central cavity, NGC 2244 and NGC 2237 are almost devoid of Class I sources, indicating that
star formation has ceased in this area. On the other hand, in an annulus around the centre with radii of 11-16 pc, roughly coinciding with the expanding HII front, about 30% of the YSOs are Class I, a clear sign of ongoing
star formation. Other groups further out in the cloud also exhibit a high Class I ratio. Similar patterns are seen in the disk fractions. Our results are consistent with possible triggering by the expanding HII region, combined with
star formation beyond the ionisation front.
Read the full abstract ▾
All authors Daniel Capela, Aleks Scholz, Koraljka Muzic, Herve Bouy, Belinda Damian, Victor Almendros-Abad, Amelia Bayo
Astrophysics of Galaxies
A New Sample of Closely Separated Dual and Binary AGN Candidates Revealed with the Radio Fundamental Catalog
Emma Schwartzman, Ryan Pfeifle, Tracy Clarke et al. (+3 more)
The Big Multi-AGN Catalog (BigMAC) provides the first literature-complete compilation of confirmed and candidate dual, binary, and recoiling active galactic
nuclei (AGN). The BigMAC provides a basis for the first population-wide
radio study of multiple AGN (multi-AGN). The
Radio Fundamental Catalog (RFC) is composed of four decades of Very Long Baseline Interferometry (VLBI) observations capable of resolving parsec-scale structure. All BigMAC candidate and confirmed multi-AGN were cross-matched to the RFC, highlighting a total of 241 BigMAC sources with available RFC imaging. We present the first detailed analysis of the ten systems exhibiting multiple compact components, most likely to be
radio multi-AGN. Using multi-frequency
radio and supporting multiwavelength information, we assess whether each system is more consistent with dual/binary AGN or intrinsic jet structure. The dual/binary nature of six systems is further supported by our
radio analysis, while the four remaining systems are more plausibly explained by compact jet activity. Several candidate multi-AGN systems exhibit projected separations of only a few to tens of parsecs. In many cases, the parsec-scale
radio separations are orders of magnitude smaller than the separations inferred from the observations that originally motivated their selection, emphasizing the importance of VLBI follow-up. Because all ten sources are members of the International Celestial Reference Frame (ICRF) and display significant intrinsic
radio structure, they also represent potential sources of astrometric error. This work establishes the RFC as an archival resource for characterizing the closest SMBH pairs while improving future ICRF realizations.
Read the full abstract ▾
All authors Emma Schwartzman, Ryan Pfeifle, Tracy Clarke, Nathan Secrest, Henrique Schmitt, Barry Rothberg
Astrophysics of Galaxies
The role of velocity dispersion in the Kennicutt-Schmidt relation
Chryssi Koukouraki and Konstantinos Tassis
The resolved Kennicutt-Schmidt (KS) relation is a power-law relation between the surface densities of the
star formation rate ($\Sigma_\mathrm{SFR}$) and molecular gas ($\Sigma_\mathrm{mol}$) in
star-forming
galaxies on kiloparsec scales. Despite its apparent simplicity, it exhibits substantial scatter, suggesting the influence of additional physical parameters beyond gas surface density. We investigate whether molecular gas velocity dispersion ($\Delta v$) acts as a hidden parameter in the resolved KS relation in nearby
galaxies. We use spatially resolved measurements of $\Sigma_\mathrm{SFR}$, $\Sigma_\mathrm{mol}$, and $\Delta v$ from the ALMaQUEST, EDGE-CALIFA, and PHANGS-ALMA surveys and from observations of the single
galaxy M51. We identify two groups of
galaxies based on the direction of the $\Delta v$ gradient with respect to the best-fit KS line: one in which the $\Delta v$ gradient is completely aligned with the KS line (group A) and thus does not contribute to the scatter, and one in which it has a component perpendicular to the line (group B) and contributes to the scatter. For each group, we fit the KS relation and examine the dependence of the residuals ($Res$) of the fit on $\Delta v$. In group B, we find a weak but statistically significant correlation between $Res$ and $\Delta v$, which is consistent across all surveys. A three-dimensional fit including $\Delta v$ yields $\Sigma_\mathrm{SFR} \propto \Sigma_\mathrm{mol}^{1.15} \Delta v^{-0.59}$. We conclude that there is a set of
star-forming
galaxies for which the velocity dispersion acts as a secondary parameter in the KS relation, with higher $\Delta v$ corresponding to lower $\Sigma_\mathrm{SFR}$ at fixed $\Sigma_\mathrm{mol}$. We find no obvious correlation between membership in this set and the other properties examined.
Read the full abstract ▾
Astrophysics of Galaxies
High-Priority Compact-Object Candidates in Young Clusters from the Gaia DR3 Non-Single-Star Catalog
Dejian Liu, Kangteng Chang, Yao Huang et al. (+7 more)
The search for massive compact objects such as black holes (BHs) or
neutron stars (NSs) in
star clusters is longstanding challenge in astrophysics, yet no definitive identification of such compact objects in young clusters has been reported. In this Letter, we construct a sample of high-priority candidates for follow-up investigation. By cross-matching the cluster catalog with the Gaia Non-Single-
Star database and estimating companion masses, we identify 13 systems with companion masses exceeding 1.4~$M_{\odot}$, three of which have masses above 2.1~$M_{\odot}$. Applying our newly developed Astrometric Mass-Ratio Function (AMRF) classification based on cluster-specific isochrones, we identify three systems whose companions cannot readily be explained by a single main-sequence
star or an unresolved close binary. These systems have inferred companion masses exceeding 2.1~$M_{\odot}$, suggesting that they may be high-mass compact-object candidates. Joint Gaia and radial velocity orbit fitting for a comparison subset yields companion masses broadly consistent with the astrometric estimates, supporting the use of our framework for target prioritization. These unconfirmed systems are valuable targets for multi-epoch spectroscopy, high-resolution imaging, and future Gaia epoch astrometry.
Read the full abstract ▾
All authors Dejian Liu, Kangteng Chang, Yao Huang, Yingjie Li, Xianjin Shen, Zehao Lin, Jingjing Li, Zhenyu Wu, Jianrong Shi, Ye Xu
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
Towards breaking the degeneracy between stellar ages and unresolved multiplicity
Friedrich Anders, Anna B. A. Queiroz, Sagar Malhotra et al. (+2 more)
Stellar age is the central desirable parameter we need to disentangle different Galactic formation scenarios. Nevertheless, no stellar age dating method is completely model-independent. Even in the best-case scenarios, present-day stellar age estimates are only precise to $\sim7\%$ and accurate to $\sim10-15\%$. A main drawback of state-of-the-art stellar parameter inference codes like StarHorse is that they do not take into account unresolved stellar multiplicity. Especially in the case of nearly equal-mass binaries or higher-order systems on the main sequence, properly taking into account unresolved multiplicity is imperative for the next generation of stellar surveys. Simulation-based inference (SBI) is a robust and flexible approach for dealing with complex models where traditional likelihood-based methods become unfeasible. Here we sketch how SBI can be used to obtain precise stellar ages, masses, binary mass ratios, and other stellar parameters from spectroscopic, photometric, and astrometric measurements.
Read the full abstract ▾
All authors Friedrich Anders, Anna B. A. Queiroz, Sagar Malhotra, Cristina Chiappini, Arman Khalatyan
Astrophysics of Galaxies
High velocity dust grains produced by a supernova explosion
Evgenii O. Vasiliev
Motivated by the discovery of a meteor with velocity more than 300~km/s (Afanasiev et al. 2007) we study how dust grains formed in the
supernova (SN) ejecta at its free-expansion phase can keep their high velocity obtained from the gas, where these grains were born. Using a one-dimensional spherically symmetric Lagrangian approach we follow the dynamics of grains during the interaction of a SN ejecta with the ambient interstellar gas. We found that grains larger $\sim 0.3~\mu$m can cross the SN forward shock front and reach the ambient interstellar medium. They are destroyed inefficiently, thus, their sizes remain close to the initial ones. In a diffuse interstellar gas of density $\lesssim 1$ cm$^{-3}$ grains larger as $\gtrsim 1~\mu$m move with velocity around $1-2$ thousand km/s and spread over distances exceeding $\sim 40-90$ pc from the SN origin within tens of kiloyears. In dense environment the propagation of grains is significantly suppressed: even large grains do not spread over distances greater than 50% of the current SN remnant size. Grains born close to the edge of the SN ejecta core in less-massive ejecta reach greater distances. Thus, high-velocity grains are expected to be formed in this part of the ejecta with mass lower than $\sim 3~M_\odot$ of the SN remnant evolving in a diffuse gas with density $\lesssim 1$ cm$^{-3}$. We discuss possible consequences for dust transport out from galactic disks.
Read the full abstract ▾
Astrophysics of Galaxies
Deep radio characterization of the supernova remnant G343.1-00.7
S. Loru, A. Ingallinera, C. Trigilio et al. (+20 more)
Supernova remnants (SNRs) are extended
radio sources whose morphology and
evolution are shaped by the interaction of strong shocks with the surrounding medium. We combined the 0.944 GHz Australian Square Kilometre Array Pathfinder (ASKAP) image from the Evolutionary Map of the Universe (EMU) survey with 0.088-0.200 GHz MWA-GLEAM data to characterize the integrated
radio spectrum of G343.1$-$00.7 and perform its first sensitive spatially resolved spectral analysis. We derived an integrated spectral index of $\alpha=-0.50\pm0.01$, confirming the previously reported value with improved accuracy. We redefined the
radio morphology of the remnant, providing the first morphological and spectral evidence that filamentary structures overlapping the nearby \hii\ G343.147$-$00.44 are associated with the SNR. Local brightness-brightness analysis revealed flatter-spectrum filaments along the south-eastern shell, consistent with a possible thermal bremsstrahlung contribution from radiative or partially radiative shocks. Comparison with \hi\ and CO data identified gas components kinematically consistent with the SNR distance, although no clear morphological evidence of interaction was found. The gas distribution around the \hii\ suggests an expanding \hi\ shell partially embedded within its parent molecular cloud. Theoretical models place G343.1$-$00.7 between the late Sedov and early pressure-driven phases, suggesting different evolutionary stages across the remnant. These results highlight the potential of high-resolution ASKAP observations for spatially resolved studies of poorly characterized SNRs in complex Galactic environments.
Read the full abstract ▾
All authors S. Loru, A. Ingallinera, C. Trigilio, G. Umana, D. Urošević, B. Arbutina, D. Leahy, C. Bordiu, F. Bufano, I.U. Aalia, C. Buemi, F. Cavallaro, E. Egron, M. D. Filipović, L. Heino, A. M. Hopkins, S. Lazarević, P. Leto, A. Pellizzoni, S. F. Rahman, S. Riggi, A.C. Ruggeri, T. Zafar
Astrophysics of Galaxies
Internal Structure, Not Environment, Shapes Metallicity Gradients in Low-Mass Galaxies from MaNGA
Anuroop Dasgupta, Namrata Roy, Saumyadip Samui et al. (+2 more)
Dwarf and low-mass
galaxies are highly sensitive to stellar feedback and gas flows, yet their spatially resolved gas-phase
metallicity remains poorly characterised. We measure radial gas-phase
metallicity gradients for 382
star-forming low-mass
galaxies from MaNGA DR17, spanning $7.2 \leq \log(M_{\star}/M_{\odot}) \leq 9.1$ and $z \leq 0.05$. Spectra are stacked in elliptical radial bins and
metallicity is derived from the N2 index. After removing the primary dependence on local stellar mass surface density, we define a residual
metallicity $\Delta Z$ to isolate secondary dependencies. Gradients are flat on average (median slope $-0.007$\,dex\,$R_e^{-1}$). The residual gradients correlate most strongly with light concentration ($r = 0.304$, $r^2 = 0.092$, $p < 0.001$) and gas velocity dispersion ($r = 0.204$, $p < 0.001$), though both account for at most 9 per cent of the variance. Large-scale environment shows no significant correlation. The concentration result is robust to measurement uncertainties and persists with a stricter resolution cut, suggesting internal structural properties shape the radial metal distribution in low-mass
galaxies.
Read the full abstract ▾
All authors Anuroop Dasgupta, Namrata Roy, Saumyadip Samui, Ritaban Chatterjee, Fuyan Bian
Astrophysics of Galaxies · Cross-listed from astro-ph.IM
ArxSP: A Python-Based Modular Application for the Reduction of Digitized Archival Spectra
Ildana Izmailova, Adel Umirbayeva, Manas Khassanov et al. (+2 more)
We present a methodology for the reduction of archival spectral data together with the description of a newly developed Python-based software package featuring an interactive graphical interface. The work is primarily aimed at processing spectra obtained with electron-optical converters (EOCs), which are characterized by
geometric distortions induced by the
magnetic field of the registration system. Such data are preserved, in particular, in the archive of the Fesenkov Astrophysical Institute (FAI), which contains about 10,000 photographic plates. These distortions, along with the need to transform the optical density of the photographic material into relative intensity, cannot be corrected by standard astronomical packages such as IRAF and therefore require a dedicated approach. Historically, reductions at FAI were performed using a program written in the Microsoft QuickC
language for computing platforms of the 1990s, rendering it incompatible with modern operating systems. The new package is implemented with the PyQt5 framework, retaining the logic of the original code while extending its functionality. The implemented
algorithms include image rotation and cropping,
geometric distortion correction, construction of the characteristic curve linking optical density and intensity, and direct conversion of pixel values in object spectra. The developed software ensures reproducible reduction of archival spectra and provides a cross-platform environment with potential for further extensions.
Read the full abstract ▾
All authors Ildana Izmailova, Adel Umirbayeva, Manas Khassanov, Laura Aktay, Saule Shomshekova
Astrophysics of Galaxies
The impact of primordial magnetic fields on the formation of galaxies
Yao-Yu Li, Shihong Liao, Yue-Lin Sming Tsai et al. (+1 more)
Primordial
magnetic fields (PMFs), potentially generated during
cosmic inflation or early-universe phase transitions, can modify
cosmic structure formation by enhancing the post-recombination matter power spectrum. In this work, we investigate the impact of PMFs on
galaxy formation using a suite of high-resolution cosmological hydrodynamical simulations evolved to $z=0$. Our simulations are initialized with PMF-induced enhancements to the matter power spectrum and include more comprehensive baryonic subgrid models than previous work, incorporating both stellar and AGN feedback. We find that PMFs systematically accelerate early structure formation, producing more abundant
halos and
galaxies, higher baryon fractions, enhanced
star formation rates, and rapid growth of supermassive black holes at high
redshifts ($z \sim 10$). However, the resulting enhanced stellar and AGN feedback efficiently processes and expels gas, reducing the late-time differences between PMF and standard $\Lambda$CDM models. The PMF signatures are therefore strongest at high
redshift and gradually weaken toward low
redshift as nonlinear
evolution and baryonic feedback dominate over the initial PMF-induced enhancements. The impact of PMFs depends strongly on the characteristic peak scale, $k_{\rm peak}$, of the initial power enhancement, with models yielding similar non-linear
evolution if they share a similar $k_{\rm peak}$, even when other PMF parameters differ. Our results highlight the critical role of comprehensive baryonic physics in accurately quantifying PMF signatures.
Read the full abstract ▾
All authors Yao-Yu Li, Shihong Liao, Yue-Lin Sming Tsai, Yi-Zhong Fan
Astrophysics of Galaxies
AGC 322753: a Dark Galaxy Candidate detected by ALFALFA and FASHI
Marco Monaci, Duncan A. Forbes, Warrick J. Couch et al. (+1 more)
We report the possible detection of a Dark
Galaxy Candidate (DGC; AGC 322753), via the cross-matching of the Arecibo Legacy Fast ALFA (ALFALFA) and the FAST All Sky HI (FASHI) HI blind surveys. It is detected by both surveys at the same recessional velocity, with a comparable HI mass of $2\times10^{9}$ M$_\odot$, and with similar HI spectral features. The ALFALFA and FASHI spectra show a double-peaked profile, compatible with a disc-like ordered rotation, and an HI linewidth at 50 per cent of the peak ($W_{50}$) of $\sim$85 km s$^{-1}$. The common intersection of the two beams allows the source position to be constrained with much greater precision than in either survey individually. Being detected by both
radio telescopes, a
Radio Frequency Interference (RFI) origin is excluded. No evidence of an optical counterpart was found down to $\sim$27.5 mag arcsec$^{-2}$ in the DESI Legacy Imaging Surveys, which leads to a stellar mass limit of $M_\star \lesssim 5\times10^{7}$ M$_\odot$. Given this stellar mass limit, AGC 322753 has $M_{\rm HI}/M_\star \gtrsim 40$. The HI mass is higher than expected for totally starless
haloes; this could imply that AGC 322753 is not completely 'dark' but could host a luminous counterpart below the current optical detection limit.
Read the full abstract ▾
All authors Marco Monaci, Duncan A. Forbes, Warrick J. Couch, Jean P. Brodie
Astrophysics of Galaxies
Stacked strong and weak lensing united: Improved measurement of the stellar and dark matter distributions in massive early-type galaxies at $z\sim 0.5$
Momoka Fujikawa and Masamune Oguri
We present a new measurement of the stellar and dark matter distributions in massive early-type
galaxies at
redshift $0.4<z<0.6$ by combining stacked strong and weak
lensing measurements. The stacked weak
lensing measurements down to the small radius of $0.013\,\mathrm{Mpc}/h$ enabled by the Subaru
Telescope Hyper Suprime-Cam data are combined with stacked enclosed projected mass measurements from 13 strong lens systems. We find that adding strong
lensing constraints improves constraints on the stellar and dark matter distributions. The central dark matter profile is found to be consistent with the standard Navarro-Frenk-White density profile. The stellar initial mass function is found to be bottom-heavy. The total density profile in the inner region is described well by the power-law density profile with the slope of $-1.96\pm 0.07$, which can also explain weak
lensing signals out to $1\,\mathrm{Mpc}/h$ reasonably well. The stacked weak
lensing profile constrains an internal mass-sheet transformation parameter to $\lambda_{\mathrm{c}}=0.978\pm0.010$. Our analysis demonstrates that the combination of the stacked strong and weak
lensing serves as a powerful tool for studying central density profiles of
galaxies.
Read the full abstract ▾