Astrophysics of Galaxies · Cross-listed from astro-ph.SR
Infrared-excess sources in VVV: candidate debris discs, SED characterization, and variability analysis
P. Esteves, R. K. Saito, C. Chavero et al. (+9 more)
Debris disks around main-sequence
stars provide important insights into planetary formation and
evolution; however, identifying these systems in the Galactic plane, where high interstellar extinction and source crowding are significant, remains challenging. Deep, wide-area surveys such as the VISTA Variables in the Via Lactea (VVV) ESO Public Survey provide multi-epoch infrared observations, enabling systematic searches in these environments. We present a method to construct a refined sample of main-sequence candidates by cross-matching data from Gaia DR3, GLIMPSE, DECaPS, and VIRAC2, to identify infrared excesses through spectral energy distribution (SED) analysis, and to analyse time-series data to detect variability potentially associated with circumstellar material or other astrophysical phenomena. Although infrared excess is commonly associated with debris disks, contributions from unresolved binaries or line-of-sight contamination cannot be excluded. Applying this methodology to the VVV tile d077 using the VIRAC2 catalogue, we analyse an initial sample of 879,556 sources and identify 446 sources flagged by the VO SED Analyser (VOSA) excess-detection
algorithm as having infrared excess, of which 171 show candidate periodic variability in the VIRAC2 Ks-band light curves. We further perform SED fitting using theoretical models to derive physical parameters and approximate spectral types for these sources. This work provides a catalogue of infrared-excess candidates in a Galactic field affected by high extinction, along with a reproducible method suitable for future large-scale applications.
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All authors P. Esteves, R. K. Saito, C. Chavero, V. Fermiano, D. Minniti, B. W. Borges, C. Cáceres, Z. Guo, V. D. Ivanov, R. G. Kurtev, D. Quispe, R. M. Torres
Astrophysics of Galaxies · Cross-listed from astro-ph.CO
TDCOSMO XXIX: JWST/NIRSpec IFU Spatially Resolved Kinematics of Three Time-delay Lenses
Shawn Knabel, Pritom Mozumdar, Anowar J. Shajib et al. (+8 more)
Spatially resolved stellar kinematics are critical to the high precision achieved by cosmological probes utilizing time delays of strongly lensed
quasars. Combined with high-resolution imaging and lens modeling, dynamical models of the 2D resolved kinematics of the deflector
galaxy tightly constrain the mass profile and break the mass-sheet degeneracy, in turn providing tight constraints on the Hubble constant when the time delays are included. We extract stellar kinematics of the deflector
galaxies in the quadruply lensed
quasar systems HE0435-1223, PG1115+080, and WFI2033-4723 from James Webb Space
Telescope Near-Infrared Spectrograph (JWST-NIRSpec) integral field spectroscopy. The kinematic maps reach average per-bin total (statistical and systematic) uncertainties of 6-11%, with average bin-to-bin correlated errors of only $\sim 1.2\%$. The aperture-integrated velocity dispersions are statistically consistent with the values used in the previous TDCOSMO analysis (all within $0.9\sigma$), with their average uncertainty reduced from 3.7% to 2.4% owing to improvements in the data reduction and kinematic-extraction methodology. We classify PG1115+080 as a fast rotator, HE0435-1223 and WFI2033-4723 as slow rotators within the probed radii, and we refine the source
redshifts from the kinematics of the lensed host
galaxies. Kinematic maps will be combined with time delays, lens models, and line-of-sight convergence estimates to measure cosmological parameters in the upcoming TDCOSMO 2026 milestone publication.
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All authors Shawn Knabel, Pritom Mozumdar, Anowar J. Shajib, Tommaso Treu, Devon M. Williams, Michele Cappellari, David Law, Simon Birrer, Takahiro Morishita, William Sheu, Massimo Stiavelli
Astrophysics of Galaxies
Same galaxy, different CGM: how the metal loading of galactic winds regulates the baryon cycle in Milky Way-mass galaxies
Prachi Khatri, Freeke van de Voort, Rebekka Bieri et al. (+5 more)
The circumgalactic medium (CGM) is both the reservoir of gas that fuels
star formation and
galaxy growth, and the repository for the mass, energy, and metals expelled through stellar
evolution and feedback. We present a controlled experiment using a suite of five cosmological magnetohydrodynamical simulations of a Milky Way-mass
halo from the Auriga suite, where we vary the metal content and energy loading of galactic winds driven by stellar feedback. We chose these parameters in combination such that all five runs obtain very similar (within $\approx$10%) $z=0$ stellar masses and morphologies and thus produce similar amounts of metals throughout their lifetimes. Our simulations differ substantially in where these metals end up, spatially within the
halo and across the different baryonic components (
stars, gas disc, CGM, and the intergalactic medium). The metal content affects the cooling efficiency of the
halo gas, regulating the CGM cool gas fraction and the
accretion rates onto the
galaxy. Between our two extreme models, we report an order of magnitude difference in the median gas
metallicity at vertical heights $|z| \gtrsim 30$ kpc above the disc plane. Current constraints on the
metallicity of the Milky Way
halo gas from absorption-line measurements of intermediate- and high-velocity clouds at $|z| \lesssim 15$ kpc are broadly consistent with our simulations, though a direct comparison is limited by differences in the adopted methods. Our findings show that
galaxies with nearly identical stellar content and morphology can differ substantially in their CGM, which offers a promising avenue for constraining feedback physics within
galaxy formation models.
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All authors Prachi Khatri, Freeke van de Voort, Rebekka Bieri, Rüdiger Pakmor, Robert J. J. Grand, Thomas A. Rintoul, Maria Werhahn, Rosie Y. Talbot
Astrophysics of Galaxies
Evolution of bar-induced dark gaps in galaxy discs: evidence of strong bar-driven effects already at $z > 2$
Susnata Chattopadhyay, Soumavo Ghosh, Dimitri A. Gadotti et al. (+5 more)
The properties of stellar bars play a crucial role in determining the bar-driven secular
evolution in disc
galaxies. However, a systematic observational study of the
evolution of several bar properties (such as strength and length) across
cosmic time is largely missing. In this paper, using a sample of $625$ barred
galaxies, taken from SDSS, HST COSMOS, and JWST CEERS surveys, we systematically investigate the
evolution of bar properties over
redshifts ($0.02 \lesssim z < 3$) by making a novel usage of dark gap (preferential light deficit along the bar minor axis) properties as a proxy for bar properties. We show that the dark gap strength ($\Delta \mu_{\rm max}$) exhibits a weak
evolution, increasing from higher
redshifts ($z \sim 2.5$) and slightly declining towards lower
redshifts ($z < 0.05$). Conversely, the extent of dark gaps ($R_{\rm DG}, R_{\rm dark}$; normalised by bar length) decreases moderately from $z \geq 1.4$ and remains constant thereafter. Our results suggest that bar formation and the initial rapid growth phase occur before $z \sim 3$, followed by mild growth towards lower
redshifts. We also find $R_{\rm dark}$ to be a better proxy (as compared to $R_{\rm DG}$) for estimating bar length, supporting earlier theoretical studies. Furthermore, the $\Delta \mu_{\rm max}$ shows a weak but statistically significant correlation with bar-to-total light ratio (Bar/T) and bar ellipticity ($\epsilon_{\rm bar}$). Studies of the
redshift evolution of bar properties over such an extensive
redshift range as done here are instrumental in constraining the bar-driven
evolution at early
cosmic times.
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All authors Susnata Chattopadhyay, Soumavo Ghosh, Dimitri A. Gadotti, Zoe A. Le Conte, Taehyun Kim, Virginia Cuomo, Camila de Sá-Freitas, E. Athanassoula
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
Multi-epoch Detection of an Ultra-fast Inflow in ESP 39607: Evidence for an Accretion Cascade
Alessandro Peca, Michael J. Koss, Roberto Serafinelli et al. (+10 more)
We present simultaneous XRISM, XMM-Newton, and NuSTAR observations of ESP 39607, a Seyfert 2
galaxy at $z = 0.201$. XRISM/Resolve reveals two absorption features near 4.7 and 4.9 keV in the observed frame, consistent with redshifted Fe XXV He-$\alpha$/Fe XXVI Ly-$\alpha$ absorption from gas inflowing at $v_{\rm in} \simeq 0.16c$. The high velocity identifies the absorber as an ultra-fast inflow (UFI), which is detected at $\sim 3$-$3.7\sigma$ across different methods and continuum models. Photoionization modeling yields $\log \xi/{\rm erg\,s^{-1}\,cm} \simeq 3.7$-$3.8$ and a column density $\log N_{\rm H,abs}/{\rm cm^{-2}} \simeq 23.2$-$23.8$, the latter depending on the assumed
metallicity. The inflow velocity and line properties are consistent with those reported from two earlier NuSTAR epochs, indicating that similar inflowing material was present over a baseline of at least 2.2 yr in the source rest frame. Across all three epochs, the combined detection significance of the UFI is $5.3\sigma$. Given the dynamical timescale of a few days at the inferred radius, $R \simeq 49$-$77\,R_{\rm g}$, the multi-year evidence favors a scenario in which the inflow is continuously replenished, forming an
accretion "cascade", rather than a single long-lived cloud. With an estimated mass inflow rate of $\dot{M}_{\rm in} \simeq 0.3$-$1.4\,M_\odot$ yr$^{-1}$, depending on
metallicity, and a ratio $\dot{M}_{\rm in}/\dot{M}_{\rm acc} \simeq 0.2$-$1.0$, the inflow could supply a substantial fraction of the
accretion needed to power the central active galactic
nucleus.
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All authors Alessandro Peca, Michael J. Koss, Roberto Serafinelli, C. Megan Urry, Claudio Ricci, Keigo Fukumura, Massimo Gaspari, Elias Kammoun, Alessia Tortosa, Giulia Cerini, Peter G. Boorman, Richard Mushotzky, Quirino D'Amato
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
The scarcity of white dwarf-brown dwarf binaries in the solar neighbourhood: A population synthesis study
Alejandro Santos-García, Santiago Torres, Alberto Rebassa-Mansergas et al. (+3 more)
White dwarf–brown dwarf (WD–BD) binaries are intrinsically rare systems that provide a unique opportunity to study binary
evolution and the formation of substellar companions. Despite recent observational progress, only a small number are known in the solar neighbourhood. We investigate whether their scarcity can be explained by binary formation and
evolution together with observational selection effects. We extend the MRBIN binary population synthesis code into the substellar regime by incorporating brown dwarf evolutionary models and an extended initial mass function. We simulate the stellar population within 100 pc of the Sun and compare the predicted WD–BD population with the observed sample. Our simulations predict 13+-5 WD–BD systems within 100 pc, consistent with observations. These systems represent only 0.1% of the local white dwarf population, confirming their rarity. The models reproduce the overall distributions of white dwarf masses, temperatures, and orbital periods, although the simulated brown dwarfs are systematically hotter than observed. Close WD–BD binaries are underproduced with the standard common-envelope efficiency 0.3, suggesting that higher efficiencies may be required to reproduce the observed short-period systems. The simulations also reproduce the observed deficit of systems at intermediate orbital periods between post-common-envelope binaries and wide non-interacting systems, as well as a weakened brown dwarf desert in main-sequence–brown dwarf binaries.
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All authors Alejandro Santos-García, Santiago Torres, Alberto Rebassa-Mansergas, Sarah L. Casewell, Zhangliang Chen, Hongwei Ge
Astrophysics of Galaxies
Classical Cepheids in the Nuclear Stellar Disk: membership via dynamical analysis
M. De Leo, M. Zoccali, R. Albarracin et al. (+2 more)
(abridged) Four classical Cepheids have been associated to the Nuclear Stellar Disk (NSD), suggesting a burst of
star formation 20 Myrs ago. In this work, we analyse all available data for these four Cepheids in order to gauge if they are bona fide members of the NSD or interlopers in the region. This allows to confirm or rule out the
star formation burst hypothesised in the literature. Our dynamical analysis is based on an updated MWpotential that includes all components of the inner
Galaxy. We conduct a thorough study of possible systematics, taking into account both observational errors and model dependencies. Our results suggest that only one Cepheid likely belongs to the NSD, while the orbits of other two extend well beyond it. Accounting for observational uncertainties, only 23-28 percent of the realisations sourced from the error distributions for the latter two are compatible with the NSD. For the fourth there are no proper motion measurements available and the light curve analysis puts into question its classification as a classical Cepheid. Through a comprehensive dynamical analysis of available data on the Cepheids attributed to the NSD, we gauged their membership to this structure. Out of the three Cepheids analysed in unprecedented depth, GCC-a is likely a member of the NSD while both GCC-b and GCC-c do not seem dynamically linked to it. Factoring in the observational uncertainties, a non-negligible percentage of the realisations for GCC-b and GCC-c are still compatible with the NSD, thus membership cannot be completely excluded for either with current data. The robust association of only one Cepheid casts doubt on the occurrence of a
star formation episode in the NSD, about 20 Myrs ago.
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All authors M. De Leo, M. Zoccali, R. Albarracin, B. Acosta-Tripailao, J. Minniti
Astrophysics of Galaxies
Bridging integrated-light and resolved-star studies of Local Group dwarf spheroidals. A novel use of deep imaging based on amateur telescopes
Sergio Guerra Arencibia, Ignacio Trujillo, Mireia Montes et al. (+4 more)
Low-mass
galaxies beyond the Local Group can only be studied through their integrated light, yet it remains unclear whether structural parameters inferred from integrated light are directly comparable to those obtained from resolved-
star studies. Using new deep imaging obtained with small-aperture amateur
telescopes, we analyse the classical dwarf spheroidals Leo II, Sculptor, and Fornax, whose stellar distributions have been extensively characterised through resolved-
star studies. We find that the radial light distributions and effective radii inferred from integrated light are in excellent agreement with those derived from resolved
stars, showing that resolved-
star and integrated-light analyses can be placed within a common observational framework applicable across a broad range of distances. The two approaches are highly complementary: resolved-
star analyses trace
galaxies to very large radii but are limited by stellar crowding in their central regions, whereas integrated-light observations are insensitive to crowding and allow the inner stellar distribution to be traced to substantially smaller radii. The integrated-light analysis extends the structural analysis to radii up to an order of magnitude smaller than previous
star-counting studies while significantly reducing the scatter in the measured profiles.
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All authors Sergio Guerra Arencibia, Ignacio Trujillo, Mireia Montes, Ignacio Ruiz Cejudo, Carlos Marrero-de la Rosa, Vicente Fontana, Aleix Roig
Astrophysics of Galaxies · Cross-listed from astro-ph.CO
Gravitational Imprints of Axion Clouds on Black-Hole Orbital Dynamics
J. Ruz, V. Mungai, F. Kühnel et al. (+4 more)
Black holes of primordial or astrophysical origin immersed in
axion dark matter provide a natural laboratory for exploring the interplay between compact objects and ultralight scalar fields. While previous studies have primarily focused on superradiance and horizon-scale phenomena, the gravitational response of the surrounding
axion distribution has received comparatively little
attention. We investigate the dynamics of particles orbiting Schwarzschild and Kerr primordial black holes embedded in scalar-field dark matter
halos. Using first-order perturbation theory, we show that the ambient
halo redistributes the gravitationally bound
axion cloud, shifting the characteristic radius of the gravitational atom. Numerical integrations of timelike geodesics demonstrate that the maximum orbital response consistently occurs at this perturbed radius, establishing a direct correspondence between the microscopic structure of the
axion wavefunction and the macroscopic dynamics of orbiting particles. Our results identify a new purely gravitational signature of scalar-field dark matter around primordial black holes and provide a framework for probing mixed
axion–primordial black hole dark matter scenarios.
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All authors J. Ruz, V. Mungai, F. Kühnel, C. Köhn, E. Stamou, J. K. Vogel, B. Guichard
Astrophysics of Galaxies · Cross-listed from astro-ph.EP
Galactic tides in the Solar System within a non-axisymmetric Milky Way model adjusted to Gaia data
Alexandre Bougakov, Yassin Rany Khalil, Marc Fouchard et al. (+4 more)
Context. Galactic tides are external differential forces acting on extended systems immersed in the Galactic potential. They play a key role in the dynamics of comets in the Oort cloud. Aims. We aim to establish the strength of Galactic tides from the non-axisymmetric potential of the Milky Way revealed by the Gaia mission, and how this strength evolves along the Galactic trajectory of the Solar System. Methods. We derived expressions for Galactic tide parameters independently of any simplified trajectory for a
star in the
Galaxy or any specific
symmetry of the Galactic potential. We obtained six parameters, $G_1$ to $G_6$, that quantify the influence of tides. Using the most up-to-date Galactic potential model, extended here to three dimensions, we studied the time
evolution of these parameters along the Sun's trajectory using a statistical approach. Results. Even for Galactic trajectories featuring modest radial and vertical excursions, as investigated here, the dominant Galactic parameter, $G_3$, is found to vary by an order of magnitude along the solar trajectory. $G_1$ and $G_2$ reach up to about one half and one quarter, respectively, of $G_3$ along the solar trajectory, whilst parameters $G_4$ to $G_6$ reach up to one tenth of $G_3$. Conclusions. Contrary to what is often assumed, all Galactic tide parameters vary widely along the Galactic trajectory of the Solar System. Two consequences can be expected: First, $G_3$ directly affects the flux of observable long-period comets and the extent of the fossilised Sednoids region; second, $G_1$ and $G_2$, and to a lesser extent, $G_4$ to $G_6$, break the integrability of the dynamics, potentially affecting the long-term structure of the Oort cloud. Additionally, the new parameters $G_4$ to $G_6$, while small for the Solar System, may strongly impact extrasolar systems with a large out-of-the-plane excursion in the
Galaxy.
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All authors Alexandre Bougakov, Yassin Rany Khalil, Marc Fouchard, Melaine Saillenfest, Benoit Famaey, Paola Di Matteo, Misha Haywood
Astrophysics of Galaxies
The Neutral Atomic Hydrogen in the solar neighborhood (NeAtHood) project I. Ghost in the shell: Neutral atomic hydrogen in the extended Orion nebula
J. D. Soler, H. Beuther, S. C. O. Glover et al. (+15 more)
The Orion Nebula is the nearest site of ongoing and recent high-mass
star formation. It is a unique laboratory for studying the mass, energy, and momentum input from high-mass
stars. We present 21-centimeter emission line observations that resolve for the first time the neutral atomic hydrogen (HI) gas in the extended Orion nebula (EON) at a resolution of one arcminute, which corresponds to a physical scale of 0.12 parsecs at the standard distance to the region. Our HI emission maps reveal an expanding shell that matches the EON contours delineated by recent observations of ionized carbon ([CII]) line emission. However, our combination of single-dish and interferometric HI observations suggests 100 solar masses of material for the front hemisphere of the shell, which is lower by roughly a factor of ten than the mass inferred from [CII] observations. This discrepancy suggests that the mass of the nearest wind-blown bubble has been overestimated, although we do not rule out the possibility that a significant amount of molecular hydrogen (H_2) in the shell may account for part of the difference. Our extended 21 cm line maps also reveal uncharted structures in and around the EON. They include a probable secondary bubble and a linear protrusion extending roughly four parsecs from the shell boundary. Our results illustrate the potential of HI interferometric observations to elucidate key aspects of the multiphase structure of
star-forming regions and their connection to their surroundings.
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All authors J. D. Soler, H. Beuther, S. C. O. Glover, R. S. Klessen, J. Ott, M. Rugel, J. W. Teh, S. E. Clark, P. Goldsmith, A. Hacar, A. Socci, M. Heyer, M.-Y. Lee, C. E. Murray, D. Seifried, S. Walch, B. Godard, M.-A. Miville-Deschênes
Astrophysics of Galaxies
Can diffuse X-rays be important in driving photoionisation in molecular clouds?
E. I. Makarenko, A. V. Ivlev, S. Bialy et al. (+5 more)
The ionisation balance in molecular clouds is regulated by several ionising sources, including
cosmic rays, X-rays, and ultraviolet radiation. Their relative importance depends on the local physical conditions and on the shielding column density. We compute the contribution of the large-scale diffuse X-ray radiation field to the ionisation in molecular clouds in the absence of strong local X-ray sources, such as young
stars. Our goal is to quantify its significance relative to the Galactic
cosmic rays. Using measurements of diffuse X-ray emission from the first eROSITA all-sky survey, we estimate the depth-dependent X-ray ionisation rate in molecular clouds across different Galactic environments. We consider both the observed diffuse field and a deabsorbed field obtained by correcting for foreground Galactic attenuation using HI4PI line-of-sight column densities in a pixel-by-pixel framework. Diffuse Galactic X-rays are unlikely to dominate the ionisation balance in well-shielded molecular gas ($N_{\mathrm{H}} > 5 \times 10^{21} \mathrm{cm^{-2}}$), where
cosmic rays remain the primary ionising
agent. At low column densities, the deabsorbed diffuse X-ray field produces ionisation rate of $\zeta_X \sim 10^{-18}\mathrm{s^{-1}}$ at $N_{\mathrm H} \sim 10^{19}\mathrm{cm^{-2}}$, remaining below the lower end of Galactic
cosmic ray ionisation rate ($\sim 10^{-17} \mathrm{s^{-1}}$). The X-ray contribution decreases rapidly with increasing shielding, falling to $\zeta_{X}\sim10^{-19}\mathrm{s^{-1}}$ by $N_{\rm H}\sim10^{21}\mathrm{cm^{-2}}$ and to $\zeta_X \sim5\times10^{-21}\mathrm{s^{-1}}$ by $N_{\rm H}\sim10^{22}\mathrm{cm^{-2}}$. Diffuse X-ray may therefore contribute to the thermal and chemical structure of low-extinction material and should be considered when interpreting ionisation tracers in diffuse or cloud-envelope environments.
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All authors E. I. Makarenko, A. V. Ivlev, S. Bialy, X. Zheng, B. A. L. Gaches, P. Caselli, M. Padovani, M. C. H. Yeung
Astrophysics of Galaxies
Constraining reionization-era Ly$\alpha$ escape with JELS-MUSE: a highly complete H$\alpha$-selected sample at $z\sim6.1$
A. L. Patrick, K. J. Duncan, Z. Li et al. (+16 more)
The Ly$\alpha$ escape fraction, $f_{\rm{esc}}^{\rm{Ly}\alpha}$, probes both the interstellar medium (ISM) conditions governing ionizing
photon escape and the rising neutral fraction of the IGM through the Epoch of Reionization (EoR). Characterising the intrinsic, ISM-driven distribution of $f_{\rm{esc}}^{\rm{Ly}\alpha}$ before IGM attenuation becomes dominant is essential to interpret the observed decline in Ly$\alpha$ visibility through the EoR. We present $f_{\rm{esc}}^{\rm{Ly}\alpha}$ measurements for a highly complete, H$\alpha$-flux-limited sample of 24
star-forming
galaxies at $z \approx 6.1$, drawn from the JWST Emission Line Survey (JELS) and observed in Ly$\alpha$ with VLT/MUSE as part of the JELS-MUSE Large Area Survey. We detect Ly$\alpha$ in 12 of 24 sources and a Ly$\alpha$ emitter fraction of $X_{\rm{Ly}\alpha} = 33 \pm 12$ per cent using the canonical EW(Ly$\alpha$) $> 25 \, \mathring{\rm{A}}$ definition. Incorporating non-detections via reverse Kaplan-Meier survival analysis yields $\langle f_{\rm{esc}}^{\rm{Ly}\alpha} \rangle = 0.07^{+0.04}_{-0.03}$, consistent with an independent stacked-flux estimate of $0.08^{+0.02}_{-0.02}$. Using reionization simulations matched to the area, depth, and
redshift range of our survey, we find that all
galaxies are expected to experience broadly similar IGM transmission, so we postulate that the large scatter in $f_{\rm{esc}}^{\rm{Ly}\alpha}$ reflects genuine ISM-driven variance rather than differences in the surrounding IGM. Among the detections, higher $f_{\rm{esc}}^{\rm{Ly}\alpha}$
galaxies tend to have lower nebular dust attenuation, bluer UV slopes, and lower stellar mass, consistent with feedback-regulated escape through localised, low-column-density ISM channels around
star-forming regions. These results
benchmark intrinsic Ly$\alpha$ escape at the end of reionization, against which IGM suppression at $z > 7$ can be interpreted.
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All authors A. L. Patrick, K. J. Duncan, Z. Li, C. A. Pirie, A. M. Swinbank, L. C. Keating, S. R. Flury, R. Begley, P. N. Best, M. Brinch, A. C. Carnall, F. Cullen, J. S. Dunlop, E. Ibar, J. Matthee, D. J. McLeod, A. Puglisi, H. M. O. Stephenson, J. P. Stott
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
Stars as triggers of interstellar gas entrainment in relativistic jets
B. Longo, M. Perucho, J.M. Martí et al. (+2 more)
Low-power extragalactic jets are known to be decelerated and dissipate large amounts of energy within their host
galaxies. However, the exact process by which this occurs is still elusive. The aim of this work is to probe the role of
stars as triggers of jet mass-loading, deceleration and dissipation in Fanaroff-Riley type I
radio galaxies. This is motivated by a theoretical model that proposes that
stars interacting with the jet boundaries could facilitate entrainment of interstellar medium (ISM) gas into jets, favouring mixing and dissipation. We have performed a numerical experiment of
stars entering a relativistic flow, using a relativistic hydrodynamics code. Our setup is limited to the interaction of three
stars with the jet boundary, in order to assess the results in a limited, controlled, environment, although this number of
stars may be plausible in the inner kpc-region of a massive
galaxy. Our results allow us to estimate the amount of entrained ISM gas as the
stars enter the jet. We show that the entrainment temporally induced on scales of tens of parsecs and thousands of years by evolved
stars is comparable to the initial jet mass rate. The way in which this entrainment happens is by the creation of a low pressure region behind the stellar objects, which drags ambient gas into the jet flow. Our results confirm that
stars interacting with the jet boundaries, and acting as catalysts of ISM/shear gas entrainment, can significantly contribute to jet mass-load and deceleration.
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All authors B. Longo, M. Perucho, J.M. Martí, V. Bosch-Ramon, Y. Hoche
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
Multiplicity of Cool Stars and their Evolution
Matthew I. Swayne, Leen Decin, Theo Khouri et al. (+12 more)
Making up a sizeable portion of the galactic census, stellar multiples are experiencing a renaissance. Enabling the study of multiple strands of the study of cool
stars, stellar multiples have been found and characterised in great numbers by the missions of the last decade, allowing the exploration of stellar parameters and populations, observation of stellar interactions, studies into stellar formation and
evolution, and characterisation of circumbinary systems. This exciting explosion of science is only set to continue, with future missions set to offer even further insights into the topic. Within these proceedings we will summarise the presentations and discussions on cool stellar multiplicity within our splinter sessions at the 23rd Cambridge Workshop on Cool
Stars, Stellar Systems, and the Sun, as we examine the present state of the field and look to what the future may bring.
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All authors Matthew I. Swayne, Leen Decin, Theo Khouri, Ayush Moharana, Léa Planquart, John Southworth, Nikki J. Miller, José A. Caballero, Orsolo De Marco, Krzysztof G. Hełminiak, Swetlana Hubrig, Valentin D. Ivanov, Pierre Kervella, Thibault Merle, Dorota M. Skowron
Astrophysics of Galaxies
Inside-out growth and the kiloparsec-scale star formation main sequence for low-surface-brightness disk galaxies in MaNGA
Bing-qing Zhang, Ze-hao Zhong, Yi-nan Zhu et al. (+1 more)
Low surface brightness
galaxies (LSBGs) are very faint objects in the universe whose formation and
evolution have long remained an unresolved problem. We selected a late-type, face-on, and disk-dominated
galaxy sample from the MaNGA survey, composed of 38 LSBGs and 216 high surface brightness
galaxies (HSBGs) by adopting a central surface brightness threshold $\mu_{0}(g) = {\rm 22.0\ mag\ arcsec^{-2}}$. Based on maps derived from pipe3D products of
star-forming areas in
galaxies, we investigated the global and resolved
star formation main sequence (SFMS and rSFMS) and radial profiles of the stellar mass density ($\mathrm{\Sigma_{*}}$),
star formation rate density ($\mathrm{\Sigma_{SFR}}$), and specific
star formation rate ($\mathrm{\Sigma_{sSFR}}$). The radial profiles of $\mathrm{\Sigma_{*}}$ and $\mathrm{\Sigma_{SFR}}$ present negative gradients, while those of $\mathrm{\Sigma_{sSFR}}$ present positive gradients. Compared to HSBGs, the LSBGs show similar, flatter, and steeper slopes in $\mathrm{\Sigma_{*}}$, $\mathrm{\Sigma_{SFR}}$, and $\mathrm{\Sigma_{sSFR}}$ gradients, respectively. The very flat $\mathrm{\Sigma_{SFR}}$ gradients of LSBGs, whose slopes range from -0.1 to -0.2, indicates uniform
star formation throughout the whole
galaxy, and the positive $\mathrm{\Sigma_{sSFR}}$ gradients reflects their “inside-out” growth. Our LSBGs and HSBGs follow the same global and resolved SFMS as the full sample, and $\mu_{0}$ shows no influence on both SFMS and rSFMS. For our full sample and two subsamples (HSBGs and LSBGs), the slopes of global SFMS and rSFMS are consistent, which indicates that the SFMS still hold on a kiloparsec scale and the
star formation activities are regulated by local events. The treatment of different excitation sources in
galaxies affects the slope of the SFMS and rSFMS, and using
star-forming areas only is more advisable.
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All authors Bing-qing Zhang, Ze-hao Zhong, Yi-nan Zhu, Hong Wu
Astrophysics of Galaxies
An updated census of the Vast Polar Structure member galaxies
Alberto Manuel Martínez-García
The Vast Polar Structure (VPOS) is a thin, planar arrangement of dwarf
galaxies oriented almost perpendicular to the Milky Way (MW) disc. Since its discovery, the census of VPOS member
galaxies has progressively expanded thanks to continuous findings of new dwarfs in the vicinity of the MW and increasingly precise measurements of their phase-space coordinates. In this work, we present the largest census to date of VPOS member
galaxies, building on a sample of 73 MW dwarfs for which positional and kinematic data are available in the literature. Based on their orbital poles, we identify 22 VPOS members: 12 MW satellites, the Large Magellanic Cloud (LMC), and 9 LMC satellites. With the exception of Bootes III, Kim 1, and Sculptor, all the on-plane dwarfs are co-rotating. Our revised census increases the known VPOS member population by nearly 50%, introducing Delve 4, Kim 1, Kim 3, Eridanus III, Pictor II, and YMCA-1 (3 MW and 3 LMC satellites, respectively) as new on-plane dwarfs. From this updated census, we revise the structural parameters of the VPOS, confirming its planar ($c/a \sim$0.27) and remarkably thin ($\sim$15 kpc) nature.
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Astrophysics of Galaxies
Is the Nuclear Star Cluster a Bulge Fossil Fragment?
R. Michael Rich, Brian Thorsbro and Christian Johnson
The Milky Way nuclear
star cluster (NSC) is unlike a conventional globular cluster: it contains a broad
metallicity distribution and stellar populations formed over an extended interval, while its detailed abundances show a close connection to the inner Galactic bulge. We ask whether the NSC should instead be compared with the proposed "bulge fossil fragments" Terzan 5 and Liller 1, complex stellar systems interpreted as surviving remnants of massive structures involved in early bulge assembly. We place this comparison against the field-bulge
metallicity distribution measured by the Blanco DECam Bulge Survey and against high-resolution infrared abundance measurements in the NSC. A broad
metallicity distribution by itself is not diagnostic, because the bulge field is intrinsically broad and strongly structured. More discriminating tests are the presence of chemically narrow and age-coherent subpopulations, the relation between [alpha/Fe] and [Fe/H], light-element abundance patterns, spatial segregation, and chemo-dynamical differences among populations. Existing NSC data establish strong chemical links with the bulge but do not support a simple one-to-one analogue of either Terzan 5 or Liller 1. In particular, metal-rich alpha-enhanced
stars in the NSC provide an important contrast with the near-solar [alpha/Fe] metal-rich populations of the best-studied fossil-fragment candidates. We argue that the BFF hypothesis is most useful as a falsifiable framework for identifying an early bulge-building component within a composite NSC assembled through in-situ
star formation, migration, and cluster infall.
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Astrophysics of Galaxies
Disc-Based Estimation of the Local Dark Matter Density and Velocity Distribution in IllustrisTNG50
Hatsume Chujo, Shogo Masaki, Keiko I. Nagao et al. (+1 more)
We study the dark matter (DM) density and velocity distribution in the solar neighborhood of Milky Way-like
galaxies using the TNG50-1 run of the IllustrisTNG simulation suite. Milky Way-like
galaxies are selected according to both their
halo mass and their bulge-to-total stellar mass ratio, and the solar-neighborhood region within each
galaxy is identified from the positions and number density of
stars, so that DM particles associated with the galactic disc are extracted while contributions from the
halo component are suppressed. Averaging over the selected
galaxies, we obtain a local DM density of $\rho \simeq 0.47\pm0.02~{\rm GeV\,cm^{-3}}$, consistent with the range inferred from observations. The disc-based extraction gives a higher peak density, $0.41\pm0.02~{\rm GeV\,cm^{-3}}$, than the value $0.34\pm0.02~{\rm GeV\,cm^{-3}}$ from a simple distance-based extraction, probably because it excludes the low-density DM in the
halo. The width of the density distribution, on the other hand, is nearly unchanged. The velocity distribution is well described by an isotropic Maxwellian with a peak velocity of about $226~{\rm km~s^{-1}}$, close to the value assumed in the standard
halo model. The differences in the density and velocity distributions between our disc-based and simple distance-based extractions are not so large as to significantly affect the interpretation of direct-detection experiments.
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All authors Hatsume Chujo, Shogo Masaki, Keiko I. Nagao, Takuho Nakabayashi
Astrophysics of Galaxies
Constraints on the Intranight Optical Variability of Intermediate-Mass Black Hole Candidates
Wenwen Zuo, Hengxiao Guo, Wanling Liu et al. (+12 more)
Intermediate-mass black holes (IMBHs) provide a unique regime for studying
accretion variability at the low-mass end of the black hole population, yet their intranight optical variability (INOV) remains poorly constrained. We present a systematic investigation of INOV in an optically selected sample of IMBH candidates using high-cadence observations from the Zwicky Transient Facility (ZTF). From a parent sample of 1,447 broad H$\alpha$-selected candidates, we identify 64 IMBH candidates (median $f_{\mathrm{AGN}}\sim0.06$) with 163 intranight monitoring sessions. Apparent INOV signals identified by conventional ZTF PSF-fit photometry are largely associated with seeing-dependent changes in the relative contributions of compact nuclear and extended host components, which can mimic intrinsic short-timescale variability. In contrast, no robust INOV is detected with difference-image analysis. An ensemble structure function spanning $\Delta t\sim0.003$–$1600$ days reveals long-term variability in a small subsample of sources, whereas intrinsic variability remains unresolved at intranight timescales. Monte Carlo simulations further show that ZTF-like single-night monitoring has a low INOV recovery probability ($\sim1.2%$) for the variability amplitudes inferred from the long-term analysis. The recovery probability is primarily controlled by source brightness, AGN contribution, intrinsic variability amplitude, and photometric precision. These results demonstrate that the absence of detected INOV does not imply the absence of rapid
accretion variability, but can reflect the limited detectability of low-amplitude signals under current observing capabilities. Our findings highlight the importance of robust photometric methodologies for future high-cadence variability studies of low-mass accreting black holes.
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All authors Wenwen Zuo, Hengxiao Guo, Wanling Liu, Wenke Ren, Jingbo Sun, Patricia Arévalo, Luis C. Ho, Alok C. Gupta, Vineet Ojha, Mouyuan Sun, Shuangliang Li, Haicheng Feng, Qi Yuan, Minfeng Gu, Xuebing Wu
Astrophysics of Galaxies
The Intermediate-Mass Black Hole Reverberation Mapping Project: Scientific Overview and Sample Characteristics
Hengxiao Guo, Jiancheng Wu, Wenwen Zuo et al. (+38 more)
Recent discoveries with the James Webb Space
Telescope of massive black holes at high
redshift have highlighted fundamental questions about black hole seed formation and the coevolution of black holes with their host
galaxies. Because the initial seed population cannot yet be observed directly, nearby intermediate-mass black holes provide a complementary fossil record of black hole formation and early growth. Motivated by this opportunity, we present the Intermediate-Mass Black Hole Reverberation Mapping (IMBH-RM) project and construct a homogeneous Sloan Digital Sky Survey sample of active broad-line IMBHs by uniformly reanalyzing literature candidates with consistent spectral decomposition and black hole mass estimation. Our sample contains 192 reliable IMBH candidates at $z\lesssim0.3$ with $\log(M_{\rm BH}/M_\odot)<6$, including four particularly compelling sources with $\log(M_{\rm BH}/M_\odot)<5$. The primary goal of IMBH-RM is to obtain reliable black hole masses from direct measurements and characteristic sizes of the broad-line region and
accretion disk for a carefully selected subsample. These measurements will provide robust low-mass anchors for calibrating single-epoch black hole mass estimates and extending black hole–
galaxy scaling relations into the IMBH regime. By building a statistically meaningful reverberation-mapped sample spanning $10^4-10^6\,M_\odot$, we aim to constrain the local IMBH mass distribution and place observational constraints on competing black hole seed formation scenarios. The future Multi-Channel Imager aboard the Chinese Space-station Survey
Telescope provides a particularly promising platform for achieving these goals.
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All authors Hengxiao Guo, Jiancheng Wu, Wenwen Zuo, Ruining Tian, Xuechen Zheng, Meicun Hou, Paulina Lira, Philip G. Edwards, Vivian U, Shu Wang, Mar Mezcua, Luis C. Ho, Minfeng Gu, Tao An, Samuzal Barua, Colin J. Burke, Zhen-yi Cai, Xuheng Ding, Haicheng Feng, Alok C. Gupta, ShaSha Li, Wanling Liu, Wen-juan Liu, Ru-sen Lu, Dragana Ilić, Andjelka B. Kovačević, Yu Pan, Luka Č. Popović, Wenke Ren, Paula Sánchez-Sáez, Jamie Stevens, Jingbo Sun, Mouyuan Sun, Chizhuo Wang, Junxian Wang, Rongfeng Shen, Xuebing Wu, Yong Shi, Zhefu Yu, Zhenya Zheng, Ling Zhu
Astrophysics of Galaxies
Empirical Near-Infrared Spectral Templates from SPHEREx: Disentangling AGN and Host-Galaxy Emission
Wenke Ren, Hengxiao Guo, Zhenya Zheng et al. (+9 more)
SPHEREx conducts the first all-sky near-infrared spectral survey over 0.75-5.0 $\mu$m, spanning the transition from host-
galaxy starlight to AGN-heated
torus emission and enabling spectroscopic identification of active galactic
nuclei (AGNs). We develop a data-driven framework combining weighted non-negative
matrix factorization with forward modeling to learn empirical rest-frame templates from 2,777 normal
galaxies and 1,064 AGNs in the North Ecliptic Pole (NEP) field. The resulting 14-component dictionary contains seven
galaxy templates spanning stellar-population continua and nebular emission and seven AGN templates capturing emission lines and warm and hot
torus continua, providing an additive, operational decomposition. Inferred near-infrared host fractions correlate with independent SDSS spectral and HSC imaging decompositions (at Pearson $r=0.68$ and $r=0.59$), comparable to the SDSS-HSC correlation ($r=0.66$) and supporting the reliability of the AGN-host separation. In the NEP deep field, the same templates recover
redshifts with $|z_{\rm fit}-z_{\rm spec}| < 0.01$ for 93.0% of
galaxies and 93.5% of AGNs and distinguish
galaxies, narrow-line AGNs, and broad-line AGNs with 81.3% accuracy. At all-sky depth, classification retains 72.9% accuracy. The near-infrared coefficients also flag questionable DESI spectral classifications and
redshifts, showing how SPHEREx complements optical spectroscopy. Learned directly from survey spectrophotometry and extending beyond the $K$ band, this empirical dictionary fills a long-standing gap in near-to-mid-infrared templates and provides a data-driven foundation for population-scale studies of AGN activity and its connection to host
galaxies across the SPHEREx all-sky survey.
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All authors Wenke Ren, Hengxiao Guo, Zhenya Zheng, Minfeng Gu, Wenwen Zuo, Junxian Wang, Weida Hu, Zhen-Bo Su, Shi-Jiang Chen, Lin Long, Jiaqi Lin, Chi-Zhuo Wang