Astrophysics of Galaxies
In situ characterization of volatile and refractory hydrocarbons produced by UV photolysis of interstellar C$_2$H$_2$ ice
P. Samarth, G. Fedoseev, M. Bulak et al. (+5 more)
Acetylene (C$_2$H$_2$) is commonly observed in
star-forming regions, young stellar objects, and the Solar System. Laboratory and theoretical studies have linked this simplest alkyne to volatile hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) through UV- or
cosmic-ray-driven chemistry, but it remains unclear whether refractory material can efficiently form through solid-state reactions of C$_2$H$_2$ on dust grains. We experimentally investigate the chemical complexity induced by UV irradiation of pure C$_2$H$_2$ ice and characterize both volatile and nonvolatile photoproducts. Experiments were performed with MATRI$^2$CES under ultra-high-
vacuum conditions at 15 K using 7.2–10.2 eV
photons. UV-processed ices were monitored in situ by
laser desorption post-ionization reflection time-of-flight mass spectrometry (LDPI ReTOF-MS) combined with pulsed ion deflection (PID). Volatile and refractory products were measured in situ at 15 and 300 K, respectively. After a fluence of $3 \times 10^{17}$
photons cm$^{-2}$, corresponding to about $10^6$ years in dense clouds, large saturated and unsaturated hydrocarbons containing up to 13 carbon atoms are formed. After sublimation of the volatile products, the 300 K residue shows a rich and distinct mass spectrum consistent with refractory material containing conjugated triple (-C$\equiv$C-) and double (-C=C-) bonds. These results demonstrate that UV processing of pure C$_2$H$_2$ ice can produce substantial molecular complexity and refractory hydrocarbons under astronomically relevant conditions, with possible implications for unidentified infrared emission bands.
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All authors P. Samarth, G. Fedoseev, M. Bulak, S. Ioppolo, L. Hornekær, E. F. van Dishoeck, H. Linnartz, K. -J. Chuang
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
Proto-Planetary Nebulae Are Not the Precursors of Planetary Nebulae With Close Binary Central Stars
Todd C. Hillwig, Bruce J. Hrivnak and David Jones
Proto-planetary nebulae are considered to be the evolutionary link between AGB
stars and planetary nebulae. They possess many of the physical characteristics expected of such a link and provide valuable information about the evolutionary process in these objects. One important characteristic of proto-planetary nebulae is the prevalence of very strong bipolar and point-symmetric morphologies. In planetary nebulae, these shapes are widely considered to be the result of shaping by a binary companion. Indeed, a number of studies have shown links between strong axial or point-
symmetry in planetary nebulae and close binary central
star systems that have gone through a common envelope phase. Here, we explore whether the observed proto-planetary nebulae may be the progenitors of planetary nebulae with close binary central
stars. We find that despite the strong shaping of proto-planetary nebulae this is unlikely to be the case. We also discuss options for
evolution to close binaries and the alternatives.
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Astrophysics of Galaxies · Cross-listed from astro-ph.HE
Radiation Magneto-hydrodynamic Simulations of MRI with Zero-Net-Vertical-Flux: Necessity of Resolving the Thermal Scale For Strongly Magnetized Initial Conditions
Yi-Xian Chen, Yan-Fei Jiang and Jeremy Goodman
We perform 3D radiation magneto-hydrodynamic (RMHD) shearing-box simulations of local patches of optically thick
accretion disks, applicable to sub-Eddington active galactic
nuclei (AGN) at $\sim 1000$ gravitational radii around a supermassive black hole (SMBH) of $10^7-10^8M_\odot$. In particular, we set up zero-net-vertical-flux (ZNVF) simulations with strong net azimuthal fields ($B_y$) characterized by initial gas-to-
magnetic pressure ratio $\beta_0$. We find that $\beta_0 \sim 1$ simulations relax to the classical MRI state with steady-state $\beta\sim 10-20$ and slow periodic reversals of the mean azimuthal field (dynamo cycles), losing
memory of their initial $B_y$ configuration. The outcome of simulations starting from $\beta_0=0.1$ (superthermal
magnetic pressures) depends upon the numerical resolution as quantified by the number of grid
cells per thermal scale height $H_\mathrm{th}$. Resolved simulations ($\Delta z\le H_\mathrm{th}/5$) settle into final states similar to the larger-$\beta_0$ runs, exhibiting thermally dominated midplanes heated by MRI
turbulence and undergoing dynamo cycles. In contrast, lower resolution $\beta_0 = 0.1$ runs evolve towards states dominated by a coherent mean field, similar to what is observed in recent isothermal MHD simulations. However, those disks fail to sustain sufficient turbulent heating near the midplane and undergo runaway cooling and contraction. While such states might be sustained in global models with even lower initial $\beta_0$ and/or continuous $B_y$ injection, our results indicate that they could arise purely from under-resolving the midplane MRI dynamo that would otherwise be able to generate and emanate randomized fields. We highlight the need to resolve a fraction of the thermal scale height (the classical MRI wavelengths) for strongly magnetized initial conditions to obtain converged outcomes in RMHD simulations.
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Astrophysics of Galaxies
JADES: Dynamical Measurements of Dark Matter Halo Masses at $z \approx 7$ Using Galaxy Pairs
Zihao Wu, Daniel J. Eisenstein, Benjamin D. Johnson et al. (+13 more)
We present dynamical measurements of dark matter
halo masses at $z\approx7$ using
galaxy pairs.
Galaxy pairs in the early Universe are usually in their first infall, before substantial orbital
evolution or phase mixing. Their relative velocities closely trace the
halo mass, especially when the pair separation is near the
halo virial radius. In the TNG100 simulation, we find that dynamical mass
estimators can recover
halo masses with an intrinsic scatter of $\sim$0.2 dex. We apply this method to 10 pair systems at z=6-8 with [O III] spectroscopy from the JWST Advanced Deep Extragalactic Survey (JADES). We infer the stellar-to-
halo mass relation while marginalizing over projection effects, measurement uncertainties, and intrinsic scatter. We find a mean
halo mass of $\log\,(M_{200}/M_\odot)=11.06\pm0.21$ at $\log\,(M_{*}/M_\odot)=9$. These
galaxies do not appear to inhabit unusually massive
halos. Our results instead indicate a high stellar-to-
halo mass ratio, corresponding to an integrated
star formation efficiency of $5^{+3}_{-2}\%$, about twice the TNG100 prediction, although the current statistical significance is limited. Future observations with larger samples will tighten these constraints and directly examine whether enhanced
star formation efficiency drives the overabundance of luminous
galaxies at
cosmic dawn.
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All authors Zihao Wu, Daniel J. Eisenstein, Benjamin D. Johnson, Lars Hernquist, Sandro Tacchella, Brant E. Robertson, Santiago Arribas, Andrew J. Bunker, Qiao Duan, Jakob M. Helton, Zhiyuan Ji, Dávid Puskás, Pierluigi Rinaldi, Fengwu Sun, Hannah Übler, Yongda Zhu
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
The Solar Neighborhood LVI: The RMSTAR Catalog of the Nearest 3352 M Dwarf Systems and 305 of their Wide Companions
Madison R. LeBlanc, Tim M. Johns, Todd J. Henry et al. (+8 more)
We present the RMSTAR (RECONS M
STAR) catalog, a 25 pc volume-limited and effectively volume-complete sample of the nearest 3352 M dwarf systems and their 305 wide stellar and 9 brown dwarf companions. RMSTAR has been created using only results from Gaia Data Releases 3 (GDR3) and 2 (GDR2), Hipparcos, and ground-based discoveries of M dwarf systems that are not available in the space-based results. The wide companions are identified using only results from GDR3 and GDR2, and have separations $\rho\ge0.''46$. There are 291 primaries with stellar companions, yielding a multiplicity rate of 8.68$\pm$0.49% for these widely separated systems, with a rate of 6.86$\pm$0.44% for projected separations $s\geq30$ au, where the sample of stellar companions is complete except perhaps for a few fringe cases. It is shown that the rate of stellar companions increases from the search limit of 30,000 au down to separations of 30 au, with a large set of companions to be characterized at closer separations in future work. We determine luminosity and mass functions for all stellar red dwarfs and their wide secondaries, finding that the luminosity function displays a classic turnover at $M_G\sim11$, whereas the mass function is described by an exponential function that rises from 0.60 M$_{\odot}$ to the end of the stellar main sequence at 0.075 M$_{\odot}$. We assess the large population of close, unresolved companions to M dwarfs by analyzing several Gaia parameters, identifying 1089 (30%) individual sources as having at least one of these elevated unresolved companion indication parameters.
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All authors Madison R. LeBlanc, Tim M. Johns, Todd J. Henry, Kenneth J. Slatten, Jennifer G. Winters, Wei-Chun Jao, Aman Kar, Michele L. Silverstein, Eliot Halley Vrijmoet, Casey Rush, Andrew A. Couperus
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
Uncovering New Ionized Winds and Relativistic Hot Outflows in MCG-6-30-15 with Chandra HETG and a Bayesian Framework
Erika B. Hoffman, Anna Ogorzałek, Christopher S. Reynolds et al. (+1 more)
Active Galactic
Nuclei (AGN) feedback plays a key role in
galaxy evolution. Highly ionized outflows, detected in X-ray absorption, are a promising candidate for
quasar-mode feedback. We present a new
Bayesian analysis of 0.65 Ms of Chandra High Energy Transmission Gratings (HETG) observations of MCG-6-30-15 from 2000 and 2004. Our approach detects new wind components, improving estimates of outflow demographics and impact. These include a hot ultra-fast outflow (UFO; 0.08c), recently confirmed by XRISM but seen in HETG for the first time, which has the power to potentially influence its host
galaxy. We also detect the first potentially collisionally ionized absorbers in this source, a physical process typically not considered in previous analyses, but potentially important for wind impact and demographics. The warm absorber complex is resolved in unprecedented detail, uncovering evidence of a correlation between outflow velocity and ionization, constraining its geometry. We also confirm the presence of dust in the wind, clearly distinguishing it from the cold ISM components, which may impact wind acceleration. Our work highlights the power of applying new methods to deep, legacy HETG
datasets, and the limitations of current atomic databases when considering OIV, V, and VI K-shell transitions. Furthermore, our work establishes a baseline for decade-scale outflow variability for new observations with XRISM and NewAthena in the future.
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All authors Erika B. Hoffman, Anna Ogorzałek, Christopher S. Reynolds, Lia Corrales
Astrophysics of Galaxies · Cross-listed from astro-ph.CO
A reanalysis of the megamaser Hubble constant: from spot catalogues to peculiar velocities
Richard Stiskalek and Harry Desmond
The Hubble tension motivates careful scrutiny of the
redshift-independent distances underpinning the local distance ladder. Water megamasers afford a purely
geometric distance from orbital dynamics in an
accretion disc. For five of the six Megamaser Cosmology Project (MCP)
galaxies, we present a
Bayesian forward model that infers the angular-diameter distance and warped Keplerian disc parameters jointly from the very long baseline interferometry quasi-observables: maser spot positions, velocities, and accelerations. We then constrain $H_0$ from these distances and the host
redshifts, including a physical distance prior, modelling the
galaxy sample selection and testing a linear and a non-linear peculiar-velocity reconstruction. Accounting for peculiar velocities with the non-linear Manticore reconstruction, we infer $H_0 = 71.6 \pm 3.7$ km/s/Mpc, where the uncertainty is statistical. Relative to ignoring peculiar velocities, the linear and non-linear reconstructions lower $H_0$ by $0.8$–$1.4$ and $1.6$–$2.1$ km/s/Mpc, respectively, whereas changing the selection variable alters it by less than $1$ km/s/Mpc. We analyse the sixth
galaxy, NGC 4258, separately. Modelling its disc as eccentric and quadratically warped, we infer an angular-diameter distance of $7.558 \pm 0.073$ (stat.) Mpc, within $0.13\sigma$ of the published maser distance.
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Astrophysics of Galaxies
A dense, metal-rich absorber driven by a heavily dust-obscured galaxy: The direct evidence of CGM enrichment at $z\sim7$
Qinyue Fei, Seiji Fujimoto, Gabriel Brammer et al. (+22 more)
We report the serendipitous discovery of a dense, metal-enriched circumgalactic medium (CGM) absorber at z=7.03, together with its host
galaxy, identified along the sightline toward a red
quasar. The absorber exhibits the largest rest-frame equivalent widths and column densities observed to date at z>5, tracing a metal-enriched gaseous
halo. Using deep JWST/NIRSpec and NOEMA observations, we characterize the absorber's physical properties and identify its host, ND1, as a vigorously
star-forming
galaxy at an exceptionally close impact parameter of ~16kpc, so heavily dust-obscured that it is detected only in the longest-wavelength NIRCam bands. Detections of [OIII]$\lambda$5007, H$\alpha$, and [CII]$\lambda 158\,\mu$m emission anchor the systemic
redshift to z~7.0321, revealing a coherent ~50km/s blueshift of the absorbing gas relative to the host, suggesting outflow-driven metal transport into the
halo. The outflow velocity, combined with the measured column density, implies an outflow rate of $\dot{M}_{\rm out}=64 M_\odot\,yr^{-1}$ and a mass loading factor $\eta=3$, indicating an energetic, chemically-enriched wind launched from a dust-obscured starburst. While the overall ionization state and [Mg/Fe] ratio align with empirical
cosmic evolutionary trends, the absorber displays an enhanced carbon-to-oxygen ([C/O]) ratio. This abundance pattern suggests the nucleosynthetic yields of Population~III stellar explosions, and aligns with the host's
star-formation history extending to $z \gtrsim 8$, potentially offering a rare fossil record of primordial metal enrichment. Our findings demonstrate that intense
star-formation feedback can rapidly and efficiently pollute the CGM/IGM well into the Epoch of Reionization. The NIR-dark nature of the host further implies that rest-UV surveys may systematically miss the dusty sources that drive CGM- and IGM-scale metal enrichment in the early Universe.
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All authors Qinyue Fei, Seiji Fujimoto, Gabriel Brammer, Lise Christensen, Marianne Vestergaard, Rohan P. Naidu, Robert A. Simcoe, Norman Murray, Luis C. Ho, Ruancun Li, Volker Bromm, Javier Álvarez-Márquez, Hollis B. Akins, Yoshihisa Asada, Simona Di Stefano, Kohei Inayoshi, Vasily Kokorev, Jorryt Matthee, Romain A. Meyer, Ava Polzin, Francesco Valentino, Fabian Walter, Marcel Neeleman, Yunjing Wu, Mengyuan Xiao
Astrophysics of Galaxies
Chandra Lensing-cluster Ultradeep Extragalactic Survey (CLUES) I: A 2 Ms Point-Source Catalog of the Abell 2744 Field
Shouyi Wang, Fan Zou, Elena Gallo et al. (+10 more)
In the first paper of the Chandra
Lensing-cluster Ultradeep Extragalactic Survey (CLUES), we present an ultradeep 2 Ms X-ray survey of the Abell 2744 field constructed from 101 archival Chandra ACIS-I observations. With an exposure comparable to the Chandra Deep Fields and further boosted by strong-
lensing magnification from the Abell 2744 cluster at $z=0.3$, this field represents the third deepest extragalactic X-ray survey of the sky and also has rich synergy with extensive coverage by the Hubble Space
Telescope and James Webb Space
Telescope. We present the Chandra data reduction and detect sources in the soft (0.5-2 keV), hard (2-7 keV), and full (0.5-7 keV) bands over a total area of $369~\mathrm{arcmin^2}$. We perform dedicated image fitting with Chandra point spread functions to optimize point-source detections and improve X-ray positions and further screen the detections to address the impact of the central bright, structured intracluster medium. A total of 327 X-ray point sources are detected and cataloged, including their X-ray photometry and basic spectral properties. Detailed simulations are also conducted, based on which the expected 50% flux completeness reaches $6.3\times10^{-16}$, $2.8\times10^{-16}$, and $4.9\times10^{-16}~\mathrm{erg~cm^{-2}~s^{-1}}$ in the full, soft, and hard bands, respectively. The source number density as a function of flux is consistent with those in blank-field surveys within a factor of $\approx2$, with a slight excess above $\approx10^{-14}~\mathrm{erg~cm^{-2}~s^{-1}}$. All X-ray data products are publicly released, including the catalog, X-ray images, exposure maps, background maps, and sensitivity maps.
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All authors Shouyi Wang, Fan Zou, Elena Gallo, Bin Luo, W. N. Brandt, Yuxuan Pang, Tommaso Treu, Xue-Bing Wu, Dieu D. Nguyen, Guido Roberts-Borsani, Shengzhe Wang, Weiwei Xu, Zihao Zuo
Astrophysics of Galaxies
On the clumpy nature of super-early galaxies
A. Ferrara, B. Das, M. Kohandel et al. (+2 more)
JWST has revealed that
galaxies during the Epoch of Reionization are composed of compact stellar clumps spanning more than two orders of magnitude in mass and size. We present an analytical framework that connects the global properties of high-
redshift galactic disks to the formation, dynamical
evolution and visibility of these systems. Starting from the classical Toomre instability, we derive analytical mass-size and surface density-size relations together with, for the first time, the intrinsic clump mass spectrum obtained by integrating over the entire unstable branch of the dispersion relation. The observed clumps are naturally reproduced for turbulent velocity dispersions $\sigma\simeq 10-80\,{\rm km\,s^{-1}}$, while their location along the mass-size relation is determined by the compactness of the parent disk. The intrinsic spectrum extends over nearly two decades in mass, $5.5\lesssim\log(M_{\rm cl}/M_\odot)\lesssim7.3$, and is transformed by gas dynamical friction, which suppresses the high-mass tail ($t_{\rm df}\propto M_{\rm cl}^{-1}$) and reproduces the observed clump mass-function slope, $dN/dM\propto M^{-1.89}$.
Supernova feedback is insufficient to clear the dense natal gas, whereas radiation pressure provides a robust clearing mechanism: Ly$\alpha$ trapping dominates in dust-poor clumps and infrared trapping takes over as they become enriched. The results provide the first self-consistent analytical framework connecting the formation, statistical properties and visibility of stellar clumps in super-early
galaxies.
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All authors A. Ferrara, B. Das, M. Kohandel, A. Pallottini, E. Ntormousi
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
Unifying spatial correlation with hierarchical population inference to constrain the AGN channel for binary black hole mergers
Lucas Pouw, Lorenzo Speri, Niccolò Veronesi et al. (+1 more)
The origin of the stellar-mass binary black holes (BBHs) observed in gravitational wave (GW) events by the LIGO-Virgo-KAGRA (LVK) detectors remains uncertain. One promising formation pathway is the active galactic
nucleus (AGN) channel, in which BBHs embedded in AGN
accretion discs experience enhanced merger rates and may produce rapidly spinning black holes in the upper mass gap. Previous constraints on the AGN contribution to the LVK merger population have relied either on spatial correlations between GW localisations and AGN catalogues or on modelling the intrinsic properties of GW sources. We develop a hierarchical
Bayesian framework that unifies these approaches within a single likelihood for the fraction of AGN-hosted GW events, $f_{\rm agn}$. This framework, combined with the latest gravitational wave transient catalogue GWTC-5.0 and the electromagnetic Quaia AGN catalogue, cannot exclude an AGN contribution to the observed merger rate. For unobscured AGN in the optical and infrared bands with bolometric luminosities $L_{\rm bol}\geq\{10^{44.5},10^{45.5},10^{46.5}\}\,\mathrm{erg\,s^{-1}}$, we exclude $f_{\rm agn} \geq \{0.52,0.41, 0.61\}$ at the 95 percent credible level under our fiducial model. The methodology and results presented in this work lay down the pathway for combining the full GW posterior with electromagnetic observations to infer the properties of GW populations and AGN discs.
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All authors Lucas Pouw, Lorenzo Speri, Niccolò Veronesi, Elena Maria Rossi
Astrophysics of Galaxies
The relationship between morphology, density, and location in the cosmic web from massive to dwarf galaxies
Ilin Lazar, Sugata Kaviraj, Aaron E. Watkins et al. (+5 more)
We study how morphology relates to environment from massive to dwarf
galaxies using, for the first time, a mass-complete sample of ~13,000
galaxies, in the stellar-mass and
redshift ranges 10^8 MSun < Mstar < 10^11.5 MSun and 0.2<z<0.4, respectively. By combining HST-derived visual morphological classifications with local density and
galaxy distances from nodes and filaments, we quantify how early-type and late-type
galaxies (ETGs and LTGs) differ with respect to environment. The overall ETG fraction decreases from ~65 per cent at Mstar ~ 10^11 MSun to ~20 per cent at Mstar ~ 10^8 MSun. Regardless of morphology, lower stellar mass
galaxies lie further away from nodes and filaments than their more massive counterparts. While, at Mstar > 10^9 MSun, ETGs reside further away from nodes and filaments than LTGs, this segregation weakens as stellar mass decreases, with ETGs and LTGs exhibiting similar locations at Mstar < 10^9 MSun. This diminishing difference at lower stellar mass is likely driven by the fact that filaments have a finite extent and lower mass
galaxies, of all morphologies, lie further away from filament cores and are therefore confined to a smaller region of the filament itself. For high-mass
galaxies (where ETGs and LTGs show strong environmental segregation), greater proximity to nodes likely inhibits coherent angular momentum acquisition, while residing closer to filament cores increases the likelihood of interactions and mergers. Both make it easier to create dispersion-dominated systems, driving the sharp rise of the ETG fraction, in the high-mass regime, close to nodes (and, to a lesser extent) filaments. Our results show that
galaxy evolution is increasingly driven by internal processes as stellar mass decreases.
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All authors Ilin Lazar, Sugata Kaviraj, Aaron E. Watkins, Christopher J. Conselice, Darshan Kakkad, Thomas M. Sedgwick, Garreth Martin, Sophie Koudmani
Astrophysics of Galaxies · Cross-listed from astro-ph.IM
The OpenGadget3 Code for Cosmological Simulations
Klaus Dolag, Geray S. Karademir, Luca Tornatore et al. (+28 more)
We present the public release of OpenGadget3 (OG3), a substantially extended and re-organised version of the widely used Gadget-2/3 family of cosmological simulation codes. Since G2 was made publicly available, the absence of continued official development led to the creation of numerous, mutually incompatible developer versions of G3 across the community. This made it effectively impossible to track bug fixes, reproduce published results, or consistently credit the many individual contributors. OG3 addresses this by consolidating these disparate developments into a single, documented, and continuously maintained code base, released under the GNU GPLv3 through a GitLab repository (with an accompanying wiki), regularly synchronised with the active developer branch, and supported by a dedicated continuous-integration (CI) pipeline. OG3 retains the core algorithmic backbone of its predecessors, a Barnes&Hut oct-tree combined with a Particle-Mesh method for
gravity, and a choice of Smoothed Particle Hydrodynamics or Meshless-Finite-Mass solvers for gas dynamics, within a hybrid MPI/OpenMP parallelisation framework, extended with GPU offloading via OpenACC and OpenMP. The code integrates an extensive suite of sub-resolution and physical modules, including primordial chemistry, radiative cooling,
star formation, stellar feedback and chemical enrichment, dust formation and
evolution, black hole growth and AGN feedback, MHD, thermal conduction, physical viscosity, SIDM, and massive
neutrinos. OG3 introduces new features improving robustness, reproducibility, and usability: a flexible mixed-precision framework spanning 16- to 128-bit representations; expert-level tagged parameters with restart-time change log; extensive consistency checks against invalid configurations; and FAIR-compliant reporting of all settings, parameters, and specific publications. (shortened and abridged)
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All authors Klaus Dolag, Geray S. Karademir, Luca Tornatore, Antonio Ragagnin, Milena Valentini, Ludwig M. Böss, Frederick Groth, Giuseppe Murante, Stefano Borgani, Volker Springel, Cenanda Arido, Javier Badía, Tiago Castro, Alice Damiano, Laura Di Federico, Moritz S. Fischer, Gian Luigi Granato, Nitya Hariharan, David Klemmer, Umberto Maio, Tirso Marin-Gilabert, Ilaria Marini, Yashraj Patil, Margarita Egelhofer, Cinthia Ragone-Figueroa, Luca Sala, Cecilia Scannapieco, Ludwig D. Schmidt, Ulrich P. Steinwandel, Giovanni Tedeschi-Prades, Marc Wiertel
Astrophysics of Galaxies · Cross-listed from astro-ph.IM
IViS: Interferometric Visibility-domain inversion Software - A GPU-accelerated Python framework for joint deconvolution with ASKAP
A. Marchal, N. M. McClure-Griffiths, J. Dempsey et al. (+9 more)
Wide-field spectral-line imaging with modern
radio interferometers remains challenging when the emission is extended, multiscale, and distributed over many overlapping pointings. Accurate reconstruction requires joint treatment of the calibrated visibilities, control of image-domain regularity, and recovery of missing short spacings from single-dish data. We present IViS (Interferometric Visibility-domain Inversion Software), a GPU-accelerated Python framework for visibility-domain joint deconvolution, and assess its performance for wide-field HI imaging with the Australian Square Kilometre Array Pathfinder (ASKAP). The current model, Classic3D, reconstructs a non-parametric sky cube directly from calibrated visibilities by minimizing a regularized least-squares criterion. The forward model relies on a non-uniform fast
Fourier transform (NUFFT), supports joint deconvolution across mosaic pointings and positivity constraints, and can incorporate single-dish data through a fusion term. We validate the method using point-source, noise-only, and multiscale diffuse-emission simulations, and apply it to ASKAP observations toward the Large Magellanic Cloud (LMC). The simulations show that IViS recovers point-source flux accurately without regularization and that regularization sets the trade-off between noise suppression and effective resolution. Joint deconvolution can recover more large-scale power than linear mosaicking of independently deconvolved pointings. With single-dish information, the reconstructed power spectra closely reproduce the input sky statistics. Applied to ASKAP data, IViS yields 10h mosaics with an effective resolution of 22” and reduced residual side-lobe structure. Compared with ASKAPSoft multi-scale CLEAN for a single observing block, Classic3D exhibits fewer residual side-lobes and recovers substantially more power at low spatial frequencies.
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All authors A. Marchal, N. M. McClure-Griffiths, J. Dempsey, H. Nguyen, H. Dénes, J. Dickey, C. Lynn, Y. K. Ma, D. McConnell, M.-A. Miville-Deschênes, N. Pingel, J. Th. van Loon
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
X-ray to Mid-IR Spectral Energy Distributions: A Catalog of X-ray Selected AGNs in the XMM-COSMOS Survey
Şeyda Şen, Eda Sonbas, Ece Kilerci et al. (+4 more)
We present a component-resolved analysis of the IR–X-ray connection in a sample of 104 spectroscopically confirmed Type~1 AGN. By combining \xmm, \swift/UVOT, and new high–angular resolution \jwst/NIRCam imaging for a subset of the sources, we constructed detailed SEDs in which the IR emission was explicitly decomposed into
accretion-disk,
torus, and polar-dust components. This approach enables us to isolate the intrinsic AGN-IR luminosities with minimal host-
galaxy contamination, providing a clean assessment of the physical relationship between the
accretion flow, circumnuclear dust, and the X-ray corona. By incorporating JWST/NIRCam observations into our SED decomposition, we significantly reduce host-
galaxy contamination and isolate the nuclear infrared emission with greater fidelity, particularly at near-infrared (NIR) wavelengths. This improvement is most apparent at 1 $\mu\mathrm{m}$, where sources with JWST coverage exhibit a markedly steeper relation between $\nu$L$_{\nu}$ (2 keV) and the NIR luminosity than those without JWST data. This behavior is naturally explained by starlight dilution, whereby host-
galaxy emission dominates lower-resolution measurements.
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All authors Şeyda Şen, Eda Sonbas, Ece Kilerci, Hasan Avdan, Kalvir S. Dhuga, Ersin Göğüş, W. N. Brandt
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
A self-consistent orbital architecture for GG Tau A. I. Simultaneous orbital fitting of the hierarchical triple
A. Lacquement, H. Beust, G. Duchêne et al. (+4 more)
GG Tau $A$ is a young triple system with the close pair, $Ab_1$–$Ab_2$, and $Aa$, surrounded by a massive circumtriple disk with a large inner cavity difficult to explain in a binary framework. We aim to determine the orbital architecture and individual stellar masses of GG Tau $A$ and assess how the available astrometric and disk-based constraints restrict the range of admissible solutions. We performed a joint fit using Oracle, developed specifically for hierarchical stellar systems. All astrometric measurements were placed in a common reference frame, since the historical wide-orbit astrometry is given relative to the unresolved photocenter of the $Ab$ subsystem. The fit included one new wide-orbit astrometric epoch and a prior on the total stellar mass derived from disk kinematics. We then applied, in post-processing, an additional geometrical constraint based on the observed center of the circumtriple disk. The fit yields orbital solutions compatible with the available astrometric and disk-based constraints and provides estimates of the individual stellar masses. The additional wide-orbit epoch only marginally reduces the range of admissible solutions. By contrast, the disk-center constraint leaves the favored orbital architectures largely unchanged but significantly tightens the stellar-mass partition. This yields posterior masses of $0.521^{+0.069}_{-0.051}$, $0.106^{+0.017}_{-0.013}$, and $0.79^{+0.10}_{-0.10}$ $M_\odot$ for $Ab_1$, $Ab_2$, and $Aa$, respectively. The reported values are posterior medians with 16th–84th percentile intervals. A joint treatment of the two orbital levels is required to recover a physically meaningful architecture and constrain the individual stellar masses. The resulting solutions provide a basis for future dynamical modeling of the circumtriple disk and for testing whether the observed cavity can further constrain the system architecture.
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All authors A. Lacquement, H. Beust, G. Duchêne, C. Lawlor, C. Ginski, E. Di Folco, A. Dutrey
Astrophysics of Galaxies
Glycine in the interstellar medium revisited: Resolving conformational complexity kinetically
Judith Wurmel and John M. Simmie
Numerous attempts to detect glycine, a simple amino acid and a key building block of
proteins in all life on Earth, in the interstellar medium have so far been unsuccessful in spite of the fact that it is present in meteorites, comets and asteroids. Glycine is conformationally diverse, existing in eight different forms, and the aim is to show that interconversions, in the dark, are governed by
quantum mechanical tunnelling at temperatures from 300 K down to 10 K and to compute the rate at which these changes occur resulting in recommendations to maximise a successful outcome.
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Astrophysics of Galaxies · Cross-listed from astro-ph.SR
Stellar age is not disk age
M. Kuffmeier, A. Winter, A. Kuznetsova et al. (+2 more)
Disk fractions in
star-forming clusters decline with stellar age, and are routinely read as the lifetime distribution of primordial protoplanetary disks. We argue that this reading is not warranted, because late infall can replenish or reform disks after collapse. To formalize this, we model the disk fraction as a superposition of primordial and environmentally replenished components, with region-to-region dispersion in the supply rate. Disk fractions cannot distinguish a long-lived disk from a short-lived one that is repeatedly replenished. In Sco–Cen both reproduce the data, the replenished model marginally better. Stellar age therefore need not equal disk age, and
stars can host successive disk generations with distinct mass, orientation, and chemistry. A key test is whether regions of the same stellar age show a genuine spread in disk fractions, as environmental variation in the replenishment supply predicts.
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All authors M. Kuffmeier, A. Winter, A. Kuznetsova, M. Vioque, A. Gupta
Astrophysics of Galaxies
How Small is Large Enough? Determining Minimal Cluster Sizes for Molecule Adsorption on Interstellar Amorphous Ice
Erik C. Neyts, Christopher King, Irina Grubova et al. (+1 more)
Binding energies of molecules on ice mantles are important to understand the
evolution of molecular complexity in molecular clouds. They are often computed using density functional theory (DFT) calculations, typically on either small amorphous ice clusters or crystalline slabs. Since these calculations require an accurate description of the electronic structure, hybrid functionals with dispersion corrections, basis set superposition error corrections and zero point energy corrections are typically employed. This, however, comes at a high computational cost, so most often small ice clusters are considered, frequently containing no more than twenty water molecules or so. While several recent studies have explored binding energy distributions, the effect of finite cluster size remains insufficiently quantified. To address this gap, we perform DFT calculations using six different functionals, on ice clusters containing 10 to 100 H2O molecules, separating the direct electronic effect of cluster truncation from the geometry-relaxation effects. As probe molecules, we use CO, CO2 and NH3. These calculations demonstrate that, irrespective of the molecule and functional used, interaction energies only start to converge from thirty to forty water molecules onwards. The dispersion energy flattens out earlier, whereas induction and polarisation effects require larger clusters to stabilise, particularly at structurally confined (cavity) sites. We conclude that ice cluster sizes of at least 30-40 water molecules are needed to obtain reliable binding energies, and that cluster size is as important as the choice of the functional.
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All authors Erik C. Neyts, Christopher King, Irina Grubova, Tobe Vorsselmans
Astrophysics of Galaxies
Lyman-$\alpha$ forest 1D flux power spectrum constraints on QSO-assisted reionization models
Vid Iršič and Avery Meiksin
Recent JWST observations have revealed a large population of faint Quasi-Stellar Objects (QSOs) at
redshifts 4 < z < 6, including a highly reddened sub-population of Little Red Dots. We exploit the sensitivity of the Lyman-$\alpha$ forest 1D flux power spectrum to thermal fluctuations in the Intergalactic Medium (IGM) to place statistical constraints on the spectral properties of the QSOs. By post-processing simulated Lyman-$\alpha$ forest spectra from the Sherwood-Relics suite of Lyman-$\alpha$ forest simulations with added HeII reionization by QSOs, in conjunction with published precision measurements of the Lyman-$\alpha$ forest 1D flux power spectrum between 4.2 < z < 5.0, we find that the addition of temperature boosts of the IGM within the HeIII regions improves agreement with the measured power spectra. While the contribution of the Little Red Dot population to HeII reionization is consistent with both a mild temperature boost of $\Delta T_b=1\times10^4$ K for soft spectra QSOs and $\Delta T_b=2\times10^4$ K for hard spectra QSOs, a contribution from the larger population of faint QSOs found by JWST having $M_{\rm UV} > -21.6$ is excluded at the 2$\sigma$ level if their spectra are sufficiently hard to boost the IGM temperature in HeIII regions by $\Delta T_b=2\times10^4$ K or greater.
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Astrophysics of Galaxies
Pushing HST to the limit: Detection completeness and morphology robustness of faint galaxies in the EGS field
Limin Lai, Zhao-Yu Li, Chao Ma et al. (+3 more)
Reliable catalogs at the faint limit are essential for statistical studies of
galaxy evolution. However, detection and structural measurements of faint
galaxies remain challenging. We evaluate detection completeness and structural parameter uncertainties of faint
galaxies in the CANDELS/EGS field using mock images and observations from the HST and JWST. The framework is also applicable to large high-
redshift surveys, including Euclid, the upcoming CSST, and the Nancy Grace Roman Space
Telescope. We detect sources in the EGS F160W mosaic using a 1.5\sigma threshold and quantify detection completeness and false-detection rates with realistic mock images. Mock
galaxy-pair tests assess blending effects on both source detection and structural measurements in sersic fitting. In addition, the overlap with CEERS observations is used to derive an empirical criterion for separating true faint
galaxies from fake detections using HST photometry. We identify 72,467 sources in the CANDELS/EGS field, including 57,444 fainter than 25 mag in F160W. Detection completeness exceeds 95% for objects brighter than 25 mag but declines to <50% beyond 27 mag (with false detection rate>50%). Structure parameters from single sersic modeling are reliable down to mH = 25 mag. For
galaxies at 25<mH<27 mag, systematic biases in the sersic index reach \Delta n \approx 5-70%, while \Delta q decreases from approximately -0.03 to -0.27. Close companions (~0.3 arcsec) introduce measurable biases in recovered sersic magnitudes and shapes, while the impact becomes negligible at larger separations. An empirical criterion based on mH, F814W-F160W color, R50, and zphot separates true faint
galaxies from false detections, reaching 72% completeness and 84% purity. It yields a final catalog of 59,646 objects consistent with previous CANDELS measurements at bright magnitudes while reaching fainter limits.
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All authors Limin Lai, Zhao-Yu Li, Chao Ma, Yang Anpin Li, Luis C. Ho, Mingyang Zhuang
Astrophysics of Galaxies
The UV-to-FIR environments of nearby Type Ia supernovae with the DustPedia Galaxy Catalogue – I. Local versus global host properties
Lisa Kelsey
The ongoing use of Type Ia
Supernovae (SNe Ia) as standardisable candles relies on an additional correction for the relationship between their standardised brightnesses and host
galaxy properties. Currently, this correction is built on host stellar mass, typically derived from optical-only SED fitting, which recent analyses suggest may not fully capture the underlying environmental properties. This relationship is stronger when considering the regions closest to the SNe, rather than the
galaxies as a whole. I use a sample of SNe Ia in DustPedia
galaxies and CIGALE SED fitting to compare the local environments of 90 nearby SNe Ia against the global properties of their hosts. The UV-to-FIR coverage of DustPedia enables improved dust constraints, and helps break the age-dust degeneracy that limits optical-only studies; to my knowledge this coverage has not been previously applied to the sub-galactic regions around SNe Ia. Stellar mass and dust mass are lower locally simply because the aperture encloses less of the
galaxy; however, for colour, sSFR, and dust attenuation, local values differ from the host average by more than measurement uncertainty alone allows, with attenuation showing the strongest discrepancy ($p=6.3\times10^{-5}$). Only mass-weighted age is consistent locally and globally.
Galaxy-integrated properties therefore do not capture the true conditions at the SN location. SN siblings (sharing a host
galaxy) only emphasise this effect. Siblings sampling the same
galaxy structure, such as two SNe in spiral arms, have consistent environments, whilst others diverge. Standardising on global properties may therefore mask the differences that drive the brightness-environment relationship.
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Astrophysics of Galaxies
An ALMA Band 7 survey of SDSS/Herschel quasars in Stripe 82: II. The nature of FIR-bright quasars
Evanthia Hatziminaoglou, Hugo Messias, Duncan Farrah et al. (+5 more)
We investigate the
star formation properties and ultraviolet (UV)/optical spectral characteristics of 142 far-infrared (FIR)-bright
quasars at
redshifts 1 < z < 4 to probe supermassive black hole (SMBH) and host
galaxy co-
evolution. By combining multi-wavelength observations with high-resolution ALMA submillimeter (submm) data, we overcome source confusion and robustly constrain
star formation rates (SFRs). The inclusion of ALMA data to the Spectral Energy Distribution fitting reduces SFR estimates by ~20% for
quasars with single submm counterparts and by a factor >2 for FIR-blended multi-component systems, while reducing FIR luminosity uncertainties by ~18%. The revised host SFRs span 500 and 3000 solar masses per year (median 1080 solar masses per year), confirming these systems are extreme starbursts. The very shallow positive correlation between starburst and
accretion luminosities suggests that SMBH
accretion and
star formation in the host are not coupled on the timescales probed by the observations. Compared to the general population of FIR-faint
quasars, FIR-bright sources have a factor of three higher detection rates at 1.4 GHz, predominantly following the FIR-
radio correlation, and reduced CIV and Lya equivalent widths with unaffected MgII, suggesting AGN-driven winds that leave MgII relatively unaffected. Together, these results place FIR-bright
quasars in a brief transitional phase, bridging heavily obscured "blowout"
galaxies and optically unobscured blue
quasars, where bulge assembly and SMBH growth peak simultaneously during ongoing stellar assembly.
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All authors Evanthia Hatziminaoglou, Hugo Messias, Duncan Farrah, Anna Feltre, Dennis Koopmans, Ismael Perez-Fournon, Rhimon Souza, Lingyu Wang
Astrophysics of Galaxies
Gravitational lensing of gravitational waves by galaxy clusters
Xikai Shan, Yi-Fan Wang, Shude Mao et al. (+2 more)
Strongly lensed gravitational waves (GWs) are commonly searched for using population priors, including time-delay and magnification-ratio distributions, to suppress false alarms. Current LIGO, Virgo, and KAGRA (LVK) searches mainly adopt priors calibrated with
galaxy-scale lenses; however, these may penalize the longer time delays produced by
galaxy clusters, which could contribute 10%–20% of lensed events. Cluster member
galaxies may also perturb the macro-lens potential and alter image magnifications. We investigate the time-delay and magnification-ratio distributions of binary black hole GWs lensed by
galaxy clusters, together with microlensing systematics. In the full lensed sample, the median time delay is about 76 days for cluster lenses, compared with 6.9 days for
galaxy lenses. After imposing an SNR threshold of $\rho>8$ at LVK O4 sensitivity, the medians are 15.4 and 0.24 days. The detected cluster sample retains a long-delay tail, with 9.1% of image pairs delayed by more than 365 days and 3.3% by more than 1000 days, so
galaxy-based time-delay priors can suppress cluster-lensed pairs. By contrast, although cluster member
galaxies broaden the magnification-ratio distribution of the full cluster sample, the detected cluster- and
galaxy-
lensing samples are very similar at O4 sensitivity, suggesting little bias in candidate selection. Cluster lenses also generally produce weak microlensing distortions: only about 0.8% of single-image mismatches exceed ${\cal M}=0.03$, while 4.8% exceed the parameter-estimation threshold $1.35/\rho^2$. Thus, microlensing is subdominant for most cluster-lensed events, mainly because images often form far from the brightest cluster
galaxy, where the stellar density is low and dominated by intracluster light, although nearby satellites can locally enhance it. These results motivate a dedicated cluster-
lensing pipeline for GW
lensing searches.
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All authors Xikai Shan, Yi-Fan Wang, Shude Mao, Huan Yang, Miguel Zumalacárregui
Astrophysics of Galaxies
Supernova Kinetic Yield oN galactic Emission Tracers (SKYNET) I. Contribution of radiative supernova remnants to Galactic N + emission
Guillaume Vigoureux, Benjamin Godard, Antoine Gusdorf et al. (+1 more)
Context. The radiative stage of a
supernova remnant (SNR) constitutes approximately 90% of its lifetime. Yet, only a few tens of radiative
supernova remnants (r-SNRs) have been observed in the Milky Way, while catalogs of young SNRs in their adiabatic stage contain $\sim$ 300 -400 confirmed sources. This deficit reflects the absence of unambiguous tracers for the radiative phase, and stands as a major obstacle to understanding the impact of SNRs on the energetic balance and the chemical state of the interstellar medium. Aims. We aim to identify spectral tracers of r-SNRs to enable their individual or statistical detection across the Galactic plane, and, more generally, to quantify the collective contribution of the Galactic r-SNR population to interstellar line emission. Methods. We present SKYNET, a new predictive framework that couples a physically motivated model of individual r-SNRs, built upon a dedicated version of the Paris-Durham shock code, with a Galactic model that describes the spatial distribution of r-SNRs and the properties of the medium into which they expand. Together, these components allow SKYNET to predict the cumulative emission of Galactic r-SNRs in nearly one million spectral lines. As a first application, we compare the predictions of SKYNET with an Herschel survey of the two fine-structure lines of singly ionized nitrogen. Results. The Galactic distribution predicted by SKYNET shows that random lines of sight toward the Galactic plane inevitably intercept multiple r-SNRs, whose cumulative emission may be associated with specific spectral tracers. SKYNET successfully reproduces the longitudinal profile of N + emission along the Galactic plane, which results from the projection on the sky of the spiral arms structure. The predicted line-ratio distribution matches the mean, the dispersion, and the tail of the observed distribution, showing that the model naturally explains the unexpectedly narrow range of physical conditions of the medium responsible for the N + emission. Comparison with the observed column densities reveals that SKYNET accounts for $\sim$ 20-25% of the total Galactic N + content, demonstrating that radiative SNRs constitute a significant, and previously underappreciated, source of ionization in the Milky Way. The difference between the observed and predicted column densities could be due to the clustering of
supernova remnants into superbubbles, which is currently not taken into account by the model, and to the contribution of non-SNR sources such as H II regions. Conclusions. SKYNET offers a new framework for quantifying the cumulative emission of r-SNRs at Galactic scales that can be directly compared with observational surveys of atomic and molecular lines. The first application reveals that SNRs contribute significantly to the ionization of the ISM, highlighting a role that has largely been overlooked.
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All authors Guillaume Vigoureux, Benjamin Godard, Antoine Gusdorf, Guillaume Pineau Des Forêts
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
The study of AF And. I. Hydrogen abundance constraints and dynamically-consistent wind model of the hot state
E. O. Dedov, A. E. Kostenkov, A. S. Vinokurov et al. (+1 more)
This paper starts a series of works devoted to an in-depth study of luminous blue variable AF And in the M31
galaxy. Here we present the results of non-LTE modelling of the
star in a hot state with CMFGEN code. In addition to the $\beta$-velocity law, widely used in the analysis of stellar atmospheres, we used a velocity distribution obtained from the balance of radial forces in the wind, including centrifugal forces for several models. Such a dynamically consistent approach reduces the parameter space during modelling and, in addition, allows us to estimate the current stellar mass whose inner hydrostatic layers are obscured by a dense wind that contaminates the absorption profiles. Based on our modelling we estimate the parameters of AF And as follows: luminosity $L \approx 6.5\times10^5~\text{L}_\odot$, mass loss rate $\dot{M}$ $\approx 3\times10^{-5}~\text{M}_\odot~\text{yr}^{-1}$, terminal velocity $v_\infty \approx 300~\text{km s}^{-1}$ and effective temperature $T_{\rm eff} \approx 17~\text{kK}$. modelling of the hot state of AF And is of particular interest due to the possibility to place constraints on the ratio of hydrogen and helium abundances for further use in constructing models of the cold state of this
star. We conclude that the current hydrogen mass fraction in the wind lies in the range from $20$ to $30$ per cent. Self-consistent modelling gives the current mass $M_*$ estimation in the range $15.6 - 17.7~\text{M}_\odot$. By employing evolutionary tracks, we were able to estimate the initial stellar mass as $M_{*,~init} \approx 50~\text{M}_\odot$.
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All authors E. O. Dedov, A. E. Kostenkov, A. S. Vinokurov, A. N. Sarkisyan
Astrophysics of Galaxies
Lower central dark matter densities in nearby galaxies than predicted by simulations
Yu Lei, Ling Zhu, Meng Yang et al. (+9 more)
Baryonic feedback in hydrodynamical simulations is typically invoked to alleviate the core–cusp problem in dwarf
galaxies. Yet baryonic processes also induce adiabatic contraction of dark matter, producing overly steep density profiles and excessively high dark matter fractions in the inner regions of massive
galaxies. The dark matter distribution of
galaxies across a wide stellar-mass range is therefore a critical test for such simulations, but a comprehensive
benchmark has remained absent. Here, we consistently measure the dark matter distribution from
galaxy centres out to radii of 20–50 kpc for 136 nearby
galaxies that together span the local mass–size relation over the stellar mass interval $10^9$–$10^{11.5}\,M_{\odot}$. We identify central regions with lower dark matter densities relative to $\Lambda$CDM simulation expectations—whose extent grows from about 10 kpc to $>50$ kpc as stellar mass increases from $10^{10} M_{\odot}$ to $10^{11.5} M_{\odot}$. Although their physical origin remains unclear, these low–dark matter regions are clearly indicated by the data. Our results provide an important observational
benchmark for future hydrodynamical simulations that explore alternative dark matter models and feedback processes.
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All authors Yu Lei, Ling Zhu, Meng Yang, Giulia Despali, Zheng Zheng, Ran Li, Dandan Xu, Niankun Yu, Jesús Falcón-Barroso, Fangzhou Jiang, Glenn van de Ven, Jie Wang
Astrophysics of Galaxies
Probing the All-sky Distribution of Soft X-ray Emission Associated with the Milky Way
Kazuki Ampuku, Ikuyuki Mitsuishi, Philip Kaaret et al. (+5 more)
We present an all-sky analysis of soft X-ray emission associated with the Milky Way using HaloSat and ROSAT data, extending our previous study of five Galactic-plane regions to 330 fields across the sky. We performed uniform spectral fitting with a model including an unabsorbed Local Hot Bubble and two additional absorbed thermal components, representing emission from warm-hot and hot
plasma, while accounting for solar wind charge exchange and the
cosmic X-ray background. The warm hot component is often interpreted as emission from the circumgalactic medium, whereas the origin of the hot component remains uncertain. Individual-field fits generally favored the inclusion of the hot component, and the field-to-field temperature distributions had medians of kT = 0.19 and 0.74 keV, with 16th-84th percentile ranges of 0.17-0.21 and 0.61-0.90 keV, respectively. The corresponding 16th-84th percentile EM ranges were (1.0-8.2) x 10-2 and (0.5-4.1) x 10-3 cm-6 pc. Stacked spectra from fields within 60 deg. <= l <= 180 deg. supported the individual-field results. After excluding bright X-ray sources and large-scale Galactic structures, we modeled the EM distributions of 178 fields using a hybrid spatial framework comprising stellar emission and disk-like and
halo-like diffuse-
plasma components. The warm-hot emission was described mainly by the disk-like term, whereas the hot emission was described mainly by stellar emission with an additional
halo-like term. These results support a widespread two temperature description and suggest a composite origin for the hot emission.
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All authors Kazuki Ampuku, Ikuyuki Mitsuishi, Philip Kaaret, Kyoko Matsushita, Kotaro Fukushima, Lorella Angelini, Dimitra Koutroumpa, K. D. Kuntz
Astrophysics of Galaxies
The Study of Detailed Morphology of Milky Way Dwarf Galaxies: Draco and Boötes I
Kyosuke S. Sato, Masafumi Yagi and Sakurako Okamoto
We present a photometric study of the outer stellar structures of the Milky Way dwarf spheroidal
galaxies (dSphs) Draco and Boötes I, using deep wide-field imaging data. The old main-sequence
stars are used to trace their spatial distributions beyond their tidal radii. We derive global structural parameters and radial profiles of number density, ellipticity, and position angle from their stellar distributions. Draco and Boötes I show contrasting features. Draco shows no prominent extended stellar distribution, although weak elongations are detected toward the eastern and northwestern directions. Its stellar distribution remains relatively compact compared with its estimated Jacobi tidal radius ($r_J=57.2^{+13.5}_{-11.1}$ arcmin), suggesting that the stellar component is tightly bound by its gravitational potential. In contrast, the radial number-density profiles of Boötes I along several directions show excess from the best-fit exponential profile outside of around $r\sim20$ arcmin, near the estimated Jacobi radius ($r_J=21.6^{+9.3}_{-7.6}$ arcmin). In addition, the ellipticity of Draco decreases with radius, whereas that of Boötes I increases toward larger radii. Bo"otes I also exhibits a prominent S-shaped stellar structure extending approximately along its orbital direction. Together, the radial density excess, increasing ellipticity, and S-shaped morphology suggest that the outer stellar structure of Boötes I may trace tidal tails produced by interactions with the Milky Way. The contrasting morphologies of Draco and Boötes I further suggest that the response of dwarf
galaxies to the Milky Way tidal field may depend not only on their orbital histories, but also on the internal structure of their dark-matter
halos.
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