Astrophysics of Galaxies
Widespread Inflows Reveal Baryonic Cycling in Star-forming and Quiescent Galaxies
Hassen M. Yesuf, Ravi Joshi, Yuxuan Zou et al. (+8 more)
Cool-gas inflows, required to sustain
star formation, have been fundamental in simulations yet remained observationally elusive. Using DESI spectroscopy of ~30,000
galaxies, we identify coherent inflowing gas (~100 km/s) in 20-50% of the sample, yielding a population-level census of gas flows. We uncover a striking inversion: inflows are detected in quiescent
galaxies, whereas
star-forming systems are dominated by gravitationally bound outflows. At fixed age,
galaxies with inflows, outflows, or no/weak flows share similar masses, environments, and structures, indicating that these properties do not differentiate flow states. Instead, gas-flow state is linked to stellar population age and recent evolutionary history, consistent with age-dependent gas flows in two regimes. In some
star-forming
galaxies, elevated
star formation surface densities drive outflows that recycle on ~0.5 Gyr timescales, consistent with a galactic fountain. In quiescent systems, low-level “drizzling” inflows persist, consistent with slowly cooling enriched
halo gas and weak
radio-mode nuclear activity. Broad gas-phase
metallicity distributions—and absence of a pristine dilution signature—indicate that detected inflows are predominantly recycled or enriched. Detectability is modulated by dust, ionization, and geometry: in
star-forming disks, inflowing gas lies near the disk plane and is obscured or ionized, while outflow hosts exhibit higher dust and metal content. As
star formation declines, cold-outflow signatures weaken, and recycled or slowly cooling gas is more readily detected as inflow. Post-starburst
galaxies provide snapshots of this transition. Our results resolve the scarcity of observed inflows, provide evidence for widespread gas
accretion and recycling in present day
galaxies, and establish an observational framework linking gas flows to
star formation, chemical
evolution, and
galaxy structure.
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All authors Hassen M. Yesuf, Ravi Joshi, Yuxuan Zou, Feng Yuan, Luis C. Ho, Lin Lin, Lei Hao, Shiyin Shen, Connor Bottrell, Fulai Guo, John D. Silverman
Astrophysics of Galaxies
Recovering Ionizing Photon Escape and Galaxy Scaling Relations in the LzLCS via Si II and C II Absorption Lines and Mock Spectra from a Radiation-Hydrodynamic Simulation
John Trevino, Simon Gazagnes, Danielle A. Berg et al. (+7 more)
In this work, we use a radiation-hydrodynamic simulation of a single $\sim10^9M_{\odot}$ virtual
galaxy to study Si II and C II line profiles seen in stacked HST/COS spectra of 58
galaxies from the LzLCS+ sample. We compare stacks across three mass bins ($M_{\star} \leq 10^8M_{\odot}$, $10^8$-$10^9M_{\odot}$, and $M_{\star} \geq 10^9M_{\odot}$) and three stacking methods (mean, median, and weighted average) to a library of 22,500 mock spectra. We investigate whether the simulation can accurately mimic real gas features, reveal clear trends with
galaxy properties, and provide indirect estimates of the ionizing escape fraction ($f_{\rm esc}$). We find reasonable agreement between simulated and observed profiles ($\chi^2 < 1$) across all mass regimes. Notably, extracting line properties such as EW and $R_f$ from best-fit mock profiles provides a robust alternative to direct empirical trends, particularly in the low-S/N regime where noise frequently biases results. The simulation-based LIS features, although derived from a single virtual object, exhibit clear correlations with $M_{\star}$, SFR, and $f_{\rm esc}$, mirroring established empirical scaling relations. We find that the best-matching mock spectra predominantly originate from simulation time steps corresponding to peak UV luminosity and intense starburst phases, suggesting that these active periods generate the ISM diversity observed in
star-forming
galaxies. Finally, simulation-based estimates ($f_{\rm esc}^{\rm virtual}$) reproduce the observed mass-dependent trends in $f_{\rm esc}$ and are in close agreement with the average $f_{\rm esc}$ of the generated stacks. This simulation-based framework establishes a relevant methodology for interpreting spectroscopic observations, including inferring $f_{\rm esc}$ and characterizing physical scaling relations, in high-
redshift galaxies from the Epoch of Reionization.
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All authors John Trevino, Simon Gazagnes, Danielle A. Berg, Kaelee S. Parker, Valentin Mauerhofer, Jeremy Blaizot, Anne Verhamme, Sophia R. Flury, Anne E. Jaskot, Alberto Saldana-Lopez
Astrophysics of Galaxies
AGN-DB: A Unified Multi-Wavelength Database of Active Galactic Nuclei
Alessandro Peca, Nico Cappelluti, C. Megan Urry et al. (+29 more)
We present the Active Galactic
Nuclei Database (AGN-DB), a comprehensive, multi-wavelength catalog compiled from more than 100 publicly available AGN catalogs and samples released by the end of 2025, spanning
radio to $\gamma$-ray wavelengths. The database contains approximately 8.1 million unique sources, approximately 7.8 million of which remain after flagging stellar contaminants, and approximately 6.8 million of these are classified as AGN. Source cross-matching across catalogs is performed using Lyra, a
Bayesian likelihood-ratio framework that jointly considers positional uncertainties, source densities, and photometric information to compute posterior match probabilities. The resulting catalog provides astrometric coordinates,
redshifts, photometry, and classifications for each unique source. All multi-catalog provenance is preserved. For every property, we store the full array of values and originating catalog identifiers, enabling multi-epoch and multi-survey analyses. In this paper, we describe the AGN-DB pipeline, including the cross-matching methodology, and present the statistical properties of the v1.0 catalog. AGN-DB is designed to enable population studies, spectral energy distribution modeling, AGN classification, and variability analyses at an unprecedented scale. Its pipeline is designed to facilitate the integration of new catalogs, allowing AGN-DB to be updated regularly, with releases planned at least annually.
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All authors Alessandro Peca, Nico Cappelluti, C. Megan Urry, Zhongtian Hu, Jerry R. Bonnell, Jack McKeown, Giulia Cerini, Xulei Sun, Fabio Pacucci, Tracey Jane Turner, Peter G. Boorman, Aritra Ghosh, Connor Auge, Rebeka L. Böttger, Adi Foord, Massimiliano Galeazzi, Jeyhan S. Kartaltepe, Iver Warburton Kilmarrin, Allison Kirkpatrick, Michael J. Koss, Stephanie LaMassa, Md Mahmudunnobe, Stefano Marchesi, Lea Marcotulli, Isaac Moskowitz, Priyamvada Natarajan, Mitsunori Ogihara, Meredith Powell, David Sanders, Dominic Sicilian, Chuan Tian, Ezequiel Treister
Astrophysics of Galaxies
Resolved Dust-Gas-Metallicity relations in nearby spiral galaxies
Vidhi Tailor, Viviana Casasola, Francesco Calura et al. (+17 more)
Context: Understanding the interstellar medium (ISM) requires high-resolution, multi-component mapping to capture its complex physical structure. Nearby spiral
galaxies, with their abundant and diverse ISM, provide an ideal laboratory for such a comprehensive analysis at sub-galactic scales. Aims: We investigate dust-to-gas (DGR) and dust-to-metal (DMR) ratios as a functions of gas-phase
metallicity (Z), on spatial scales ranging from 0.6 to 2.3 kpc, in a sample of 10 nearby spiral
galaxies, spanning more than an order of magnitude in stellar mass (9.7 \le \log(M_*/M_\odot) \leq 11.0),
star formation rate (SFR, \sim 0.3–3 \, M_\odot \, \rm yr^{-1}) and
metallicity ranging from 8.3 \lesssim 12 + \log( O/H) \lesssim 8.8. We explore how the DGR-Z and DMR-Z relations are shaped by the assumptions behind the CO-to-H_2 conversion factor (\alpha_{CO}). Methods: We homogeneously combine maps of dust, atomic gas, molecular gas, and
metallicity. Motivated by the diversity in L_{CO(1-0)}/SFR ratios and
metallicity across our sample, we introduce a hybrid \alpha_{CO} prescription to distinguish between CO-bright and CO-dark regimes. The derived DGR-Z and DMR-Z relations are compared with other global and resolved observational results, and with the predictions of dust and chemical
evolution models. Results: Both DGR-Z and DMR-Z relations are dependent on the adopted \alpha_{CO} prescription, and no single \alpha_{CO} can reproduce the properties of the entire sample, motivating the use of a hybrid approach. The DGR increases with
metallicity, spanning \sim 1 dex across the sampled range; while the DMR remains approximately constant at \log(\mathrm{DMR}) = -0.53 \pm 0.13, implying that \sim 30 % of metals are locked into dust grains. This flat behavior indicates an evolved dust phase where efficient ISM grain growth drives a saturation regime balancing dust formation and destruction.
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All authors Vidhi Tailor, Viviana Casasola, Francesco Calura, Francesca Pozzi, Jacopo Fritz, Maritza Lara-López, Marco Palla, Simone Bianchi, Santiago Álvarez-Córdoba, Matteo Bonato, María Emilia De Rossi, Sami Dib, Luis E. Garduño, Andrea Giannetti, Omar López Cruz, Marina M. Puebla, Evangelos D. Paspaliaris, Leonid S. Pilyugin, Guillermo Valé, Mabel Valerdi
Astrophysics of Galaxies
Super-Eddington Accretion and Early-Stage Feedback in Ton S180
Pierpaolo Condò, Giacomo Venturi, Eleonora Parlanti et al. (+15 more)
Narrow-line Seyfert 1 (NLSy1)
galaxies are key laboratories for studying rapid supermassive black hole (SMBH) growth and active galactic
nucleus (AGN) feedback at high
accretion rates. We investigate the nearby NLSy1 Ton S180 with VLT-MUSE optical integral field spectroscopy to connect its nuclear
accretion properties with the spatially resolved ionized gas and host-
galaxy kinematics. We modeled the unresolved nuclear spectrum and applied a custom point spread function subtraction to recover the host-
galaxy emission on kiloparsec scales. The nuclear spectrum requires a complex permitted-line decomposition and a blueshifted [O III] outflow component. Single-epoch
estimators and the stellar velocity dispersion imply black hole masses in the range $\log(M_{\rm BH}/M_\odot) = 6.5 - 7.7$. Combined with the observed luminosity, this implies a dimensionless mass
accretion rate of $\dot{M} / \dot{M}_{\rm Edd} = 4.1 - 980$, confirming the extreme
accretion regime. The host
galaxy shows a circumnuclear ring, an inner elongated structure consistent with a bar, and rotation-dominated gas and stellar kinematics. Simple inflow models do not significantly better reproduce the observed velocity field. We detect a resolved ionized outflow extending about 2 kpc west of the
nucleus, with mildly blueshifted velocities (with a maximum of $v_{\rm max} \sim 340$ km s$^{-1}$). Its mass outflow rate is only $\sim 4.2 \times 10^{-4}\,M_\odot\,\mathrm{yr}^{-1}$, whereas the unresolved nuclear outflow reaches $v_{\rm max} \sim 1140$ km s$^{-1}$ and $\dot{M}_{\rm out} > 1.5\,M_\odot\,\mathrm{yr}^{-1}$. This contrast may reflect either weak ionized coupling from nuclear to galactic scales or different episodes of AGN activity over time. These results show that Ton S180 is undergoing rapid SMBH growth, while the observed ionized outflow remains confined to the inner few kiloparsecs and is weak on host-
galaxy scales.
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All authors Pierpaolo Condò, Giacomo Venturi, Eleonora Parlanti, Marco Berton, Enrico Congiu, Alessia Tortosa, Stefano Carniani, Francesco Tombesi, Tommaso Zana, Claudio Ricci, Ezequiel Treister, Luis C. Ho, Enrico Piconcelli, Miguel Coloma Puga, Emilia Järvelä, Luca Crepaldi, Amelia Vietri, Benedetta Dalla Barba
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
A Kinematic Measurement of the Effective Viscosity of the Intracluster Medium: The Cold Front of A3667 Seen by XRISM
Yutaka Fujita and Yuki Omiya
Constraints on the effective viscosity of the intracluster medium (ICM) come almost exclusively from imaging: the power spectrum of X-ray surface brightness fluctuations, and the morphology of Kelvin-Helmholtz rolls at cold fronts. Both indicate a viscosity below the isotropic Spitzer value. XRISM/Resolve opens a complementary, purely kinematic route, in which the viscosity is inferred from the thickness of the viscous shear layer that develops at a sliding contact discontinuity. We apply it to the prototypical cold front of A3667. The interface is the classical Rayleigh problem, in which momentum diffuses to a depth d in a time T, giving a kinematic viscosity \nu ~ d^2/(4T). The XRISM velocity map shows a line-of-sight velocity jump of 535 km/s across the front, completed within the 100 kpc-wide region immediately inside it, the only region with an anomalously broad line. Hence d ~< 100 kpc. Adopting interaction times set by the sizes of the interacting regions divided by this velocity, we obtain dynamic viscosities of 5.2 x 10^3 and 3.3 x 10^3 g/cm/s for the cool and the hot side of the front, or 6.4 and 0.72 times the Spitzer value. Because d is limited by the angular resolution of XRISM, and the viscosity scales as its square, these are upper limits. The kinematic constraint is consistent with, and independent of, the imaging results.
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Astrophysics of Galaxies
JWST/NIRSpec Reveals Diverse Nuclear Environments in Dwarf Galaxies Hosting AGN
Thomas Bohn, Archana Aravindan, Gabriela Canalizo et al. (+18 more)
Dwarf
galaxies, in the $\Lambda$CDM framework, are expected to dominate the
galaxy number density at all
redshifts. As such, studying AGN in these systems, including characterizing their local environments and emission properties, is essential in obtaining a comprehensive view of the AGN population and their influence on their host
galaxy. To this end, we present JWST/NIRSpec IFU observations of four dwarf
galaxies (M$_\star<$10$^{9.5}\;$M$_\odot$) with evidence of AGN activity. Utilizing the improvements in resolution and sensitivity offered by JWST, we investigate the emission features of the central kiloparsec of these dwarfs. Our findings include the detection of over 100 emission lines across our sample, including coronal lines with ionization potentials greater than 300 eV. The nuclear spectra show diverse emission features. In two
galaxies, we measure strong contributions from hot dust to the infrared continuum. We also detect both PAH and coronal line emission within 100 parsecs of the
nuclei in three
galaxies. We estimate the hot H$_2$ gas mass to be between 1–20 M$_\odot$ within 300 pc across our sample, where both thermal and non-thermal excitation are involved. Lastly, spatial flux maps reveal varied emission structures across all observed gas phases, ranging from radial
symmetry around the
nucleus to elongated plumes. Kinematic maps also show each
galaxy has unique velocity structures despite all being isolated, affirming the diversity of rotation curves problem, a long standing tension between simulations and observations. These results showcase the unique and varied nuclear environments that can be found in dwarf
galaxies hosting AGN.
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All authors Thomas Bohn, Archana Aravindan, Gabriela Canalizo, Aditya Togi, Shobita Satyapal, Tohru Nagao, Matthew Malkan, Thomas S.Y. Lai, Hanae Inami, Weizhe Liu, Marina Bianchin, Tanio Diaz-Santos, Aaron Evans, Sean T. Linden, Vivian U, Lee Armus, Loreto Barcos-Munoz, Kirsten Larson, Yiqing Song, Sabrina Stierwalt, Jason Surace
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
The DESI Data Release 1 white dwarf catalogue
Andrew Swan, Boris T. Gänsicke, Paula Izquierdo et al. (+49 more)
The Dark Energy Spectroscopic Instrument is conducting a
redshift survey, mapping the universe in three dimensions to measure the history of
cosmic expansion. As well as extragalactic objects, it is targeting millions of Milky Way
stars, including white dwarfs. Using Data Release 1 we assemble the largest catalogue of spectroscopically-confirmed white dwarfs to date, whose straightforward selection function enables statistically-robust population studies. We visually inspect and fit models to spectra of 63968 objects, finding 44409 white dwarfs. We present their spectral classifications, atmospheric parameters and radial velocities. We assess survey completeness and uniformity, identify potential spectral contamination caused by flux from nearby sources entering the fibre, and assign confidence scores to our classifications to facilitate selection of statistical and observational samples. We present spectra representing most white dwarf classes, common and exotic. We conclude with recommendations and warnings regarding the use of the catalogue.
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All authors Andrew Swan, Boris T. Gänsicke, Paula Izquierdo, Detlev Koester, Christopher J. Manser, Laura K. Rogers, Siyi Xu, J. Aguilar, S. Ahlen, C. Allende Prieto, L. Beraldo e Silva, D. Bianchi, D. Brooks, F. J. Castander, T. Claybaugh, A. de la Macorra, A. Dey, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, N. Gentile Fusillo, S. Gontcho A Gontcho, G. Gutierrez, J. Guy, K. Honscheid, K. Inight, M. Ishak, R. Joyce, S. E. Koposov, M. Landriau, L. Le Guillou, T. S. Li, M. Manera, A. Meisner, R. Miquel, J. Moustakas, S. Nadathur, J. Najita, I. Pérez-Ràfols, W. J. Percival, F. Prada, G. Rossi, E. Sanchez, D. Schlegel, M. Schubnell, H. Seo, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou, H. Zou
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
Nebular Spectra of the Extremely Metal-Poor SN II 2023ufx Over a Year After Explosion: A Massive Progenitor and Unique Circumstellar Environment
Evan Jennerjahn, Michael A. Tucker, Christopher S. Kochanek et al. (+3 more)
We present new observations of the metal-poor ($< 0.1$ $\rm Z_\odot$) Type II
supernova 2023ufx and its host
galaxy. The deep nebular spectrum, obtained roughly a year after explosion, has a triple-peaked [O I] emission profile suggesting an asymmetric explosion. Comparison to nebular spectra models suggests a zero-age main sequence mass of $ M_{\rm ZAMS} \sim 25-35$ $\rm M_\odot$, which is supported by the low [Ca II]/[O I] emission-line ratio of $\approx0.4$. The diminishing, broad, boxy H$\alpha$ emission and flattening of the light curve in the late ($\sim2$ yr) photometry suggest a complex mass-loss history in the centuries to millennia before explosion. New optical and near-infrared imaging of the host
galaxy confirms that it is a dwarf, with a stellar mass of $10^{6.6\pm0.1}$ $\rm M_\odot$ and a SFR of $10^{-2.5\pm0.1}$ $\rm M_\odot$/yr. Results from both SED fitting and
galaxy stellar mass-
metallicity scaling relations all lead to an environmental
metallicity estimate of $0.02-0.07$ $\rm Z_\odot$. Taken together, these observations confirm that SN 2023ufx is the explosion of a very metal-poor, heavily stripped red supergiant.
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All authors Evan Jennerjahn, Michael A. Tucker, Christopher S. Kochanek, Luc Dessart, Willem B. Hoogendam, Benjamin J. Shappee
Astrophysics of Galaxies
Fundamental differences in the X-ray accretion properties of low and high-excitation radio galaxies
R. Kondapally, T. Holc, J. Aird et al. (+7 more)
We characterise the
accretion rate properties of
radio-detected AGN by combining deep
radio and X-ray observations of the Boötes field. We used deep international LOFAR
telescope observations to identify 2840
radio-AGN across $0.3 < z \leq 2$, divided into samples that are complete in
radio luminosity. We further split this sample into four different classes:
radio-quiet AGN (RQ-AGN), high-excitation
radio galaxies (HERGs), and low-excitation
radio galaxies (LERGs) hosted by
star-forming (SF-LERGs) and quiescent
galaxies (Q-LERGs). Through performing X-ray stacking, we determined the average X-ray luminosities, $L_{\rm{X, 2-10\,keV}}$ and average specific X-ray luminosities, $\lambda_{sL_{X}}$ (X-ray luminosity scaled by the stellar mass; a proxy for the
accretion rate). We studied how these X-ray properties depend on
radio luminosity, stellar mass, and
redshift for each of the four AGN classes. We found that the LERGs, regardless of their
star-formation activity, show significantly lower $L_{\rm{X, 2-10\,keV}}$ and $\lambda_{sL_{X}}$ than both HERGs and RQ-AGN across all
redshifts. The average X-ray luminosities for the HERGs, RQ-AGN, and SF-LERGs typically increase with
redshift, which may be associated with the increased cold gas fractions at earlier times, resulting in more enhanced black hole
accretion. The average X-ray luminosities show weak-to-no correlation with
radio luminosity at a given
redshift, suggesting that the physical processes producing the X-ray and
radio emission may not be coupled on spatial and/or temporal scales.
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All authors R. Kondapally, T. Holc, J. Aird, K. J. Duncan, P. N. Best, D. M. Alexander, S. Das, L. K. Morabito, S. Shenoy, D. J. B. Smith
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
A targeted search for fast radio bursts from magnetars in elliptical galaxies
S. Paine, D. R. Lorimer, S. Sirota et al. (+12 more)
Motivated by predictions that globular clusters associated with nearby giant elliptical
galaxies are
prime environments for detecting fast
radio bursts (FRBs) from magnetars, we report on a targeted high-sensitivity search across five local massive elliptical
galaxies. We utilized the GREENBURST single-pulse search pipeline and the VEGAS backend on the Green Bank
Telescope (GBT) to conduct an L-band (1.4 GHz) survey for FRBs in each target environment. We discovered FRB 20240817A in the direction of M49 (NGC 4472) which has a pulse width of 15 ms, a signal-to-noise ratio of 13, and a dispersion measure (DM) of $983~\rm{cm}^{-3}$ pc. Although a
Bayesian spatial association framework initially flags M49 as the host, carefully accounting for the foreground electron column contributions from the Milky Way and both the Virgo intracluster medium and M49's hot gaseous
halo ($\sim300-400~\rm{cm}^{-3}$ pc combined) strongly disfavours a physical connection. We conclude that FRB 20240817A is a background event. We also identified a repeating cluster of three low-significance pulses from the direction of M49 at a physically plausible DM of $150-160~\rm{cm}^{-3}$ pc. Accounting for the fraction of each target's extended globular cluster distribution observed, the absence of unambiguous, host-localized bursts allows us to place a joint upper limit on the intrinsic burst rate of a single active source within these systems of $R_0 < 0.028~\rm{hr}^{-1}$ (and an integrated rate limit of $<1.0$~hr$^{-1}$ for M49), lowering previous upper limits and suggesting that magnetar formation within dynamical clusters is less efficient than previously assumed.
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All authors S. Paine, D. R. Lorimer, S. Sirota, G. M. Doskoch, S. Tabassum, M. Flanagan, J. Lituchy, A. Stone, J. W. Kania, M. Bhardwaj, S. Mehta, M. A. McLaughlin, B. Kharel, D. Agarwal, M. P. Surnis
Astrophysics of Galaxies
Absolute Motion of the Infrared Counterpart to Sagittarius A* in the Gaia Celestial Reference Frame 3 and Limits on an Intermediate-mass Black Hole Companion
Rebecca A. Lewis-Merrill, Tuan Do, Matthew W. Hosek Jr. et al. (+9 more)
We report the first proper motion and acceleration measurements of the infrared (IR) counterpart to Sagittarius A* (Sgr A*-IR), the supermassive black hole (SMBH) at the center of our
Galaxy, in the Gaia-Celestial Reference Frame (Gaia-CRF3). This reference frame realizes the International Celestial Reference System (ICRS), which is an absolute reference coordinate system defined by
quasars. A combination of Gaia and Hubble Space
Telescope data was used to transform Keck adaptive optics (AO) observations into Gaia-CRF3. We developed a method for selecting reference
stars that minimizes astrometric transformation errors (statistical error = $0.10-0.63$ mas) and drift of the coordinate system (systematic error $\sim 0.01$ mas/yr). We find the proper motion of Sgr A*-IR in Gaia-CRF3 to be $\mu_{\alpha^{*}} = -3.093 \pm 0.085$ mas yr$^{-1}$ and $\mu_{\delta}= -5.62 \pm 0.13$ mas yr$^{-1}$ with the initial position at $t_{0} = 2016.0$ of R.A. = 266.41680848 $\pm$ 0.00000029 deg and DEC = -29.00783947 $\pm$ 0.00000050 deg, which translates to a precision of 1.05 mas in R.A. and 1.79 mas DEC. This is consistent with the astrometric measurements of the
radio counterpart to Sgr A* by \citet{Xu_2022}. We also place a $2\sigma$ upper constraint of the acceleration of Sgr A*-IR on the sky at 0.061 mas yr$^{-2}$. This acceleration limit on Sgr A*-IR excludes any intermediate-mass black hole companion with mass $\gtrsim 4\times 10^{4}$ $M_{\odot}$ within a distance of $\sim$0.01 pc, consistent with previous studies. With the release of Gaia Data Release 4, we predict these limits will be improved by at least a factor of two.
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All authors Rebecca A. Lewis-Merrill, Tuan Do, Matthew W. Hosek Jr., Gregory David Martinez, Shoko Sakai, Kelly Kosmo O'Neil, Grant Weldon, Abhimat Gautam, Zoë Haggard, Andrea M. Ghez, Jessica R. Lu, Keith Matthews
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
Sgr A* as a Galactic PeVatron: Multimessenger Signatures of the Magnetic Penrose Process
Marina Cermeño, Pedro De la Torre Luque, Cristina Fernández-Suárez et al. (+5 more)
The
magnetic Penrose process (MPP) is one of the most efficient mechanisms for extracting rotational energy from a magnetized Kerr black hole (BH), enabling charged particles to reach very-high energies. We investigate this process in Sagittarius A* (Sgr A*), the supermassive BH at the Galactic center (GC), focusing on its ultra-high-efficiency regime, in which
neutrons undergo beta decay inside the BH ergosphere. As a key novelty, we compute the
neutron production spectrum in the
accretion flow directly from the nuclear reaction kinematics and follow
neutron trajectories in the Kerr spacetime to determine the population that reaches the ergosphere and undergoes the MPP. From this population, we derive the spectrum of accelerated
protons and show that Sgr A* can accelerate them up to PeV energies, strengthening its interpretation as a candidate Galactic PeVatron. We further compute the gamma-ray and
neutrino emission produced through hadronic interactions of the escaping
protons in the Central Molecular Zone. The predicted gamma-ray fluxes exhibit distinctive spectral features that could provide an observational signature of the MPP and may constitute a non-negligible contribution to the very-high-energy emission detected by H.E.S.S. and HAWC. The associated
neutrino fluxes remain below the diffuse Galactic component inferred by IceCube, but may still contribute to the high-energy emission from the GC. Remarkably, the predicted signals lie within the projected sensitivity of SWGO for all scenarios considered here and, for some models, only a factor of a few below the nominal CTAO sensitivity, while KM3NeT/ARCA and IceCube-Gen2 will provide complementary tests. Our results establish the MPP as an observable mechanism for extracting BH rotational energy, providing a direct connection between horizon-scale physics and multimessenger observations that can be extended to other magnetized BHs.
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All authors Marina Cermeño, Pedro De la Torre Luque, Cristina Fernández-Suárez, Viviana Gammaldi, Enrique Mier-Alonso, María J. Rodríguez, Miguel Á. Sánchez-Conde, Jaume Zuriaga-Puig
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
Ionized Nebulae Around Two New Symbiotic Stars: GR Cygni and [D75] 141
Howard E. Bond, Calvin Carter, Sven E. Eklund et al. (+4 more)
In the course of selecting targets for a spectroscopic survey of faint planetary-nebula
nuclei, we encountered two anomalous cases of late-type variable
stars surrounded by nebulosities discovered by amateur astronomers. We obtained follow-up deep narrow-band images of the two nebulae: StDr Objet 14 (diameter 1.5 arcmin) and StDr 4 (diameter 2.5 arcmin). StDr Objet 14 is found to be a low-excitation nebula, bright only in Ha+[N II], and showing a unique double-ring "bull's-eye" morphology. StDr 4 exhibits a bow-shock structure, bright in Halpha and [S II], embedded in an extended emission nebula. Both central
stars, respectively GR Cygni and [D75] 141, are found to be pulsating semiregular variable
stars. Our spectroscopic observations show GR Cyg to be a cool carbon
star of type C9,2, with emission lines of the Balmer series, [O II] and [O III], [Ne III], [S II], and Fe II. A synthetic narrow-band image of GR Cyg shows that the source of its strong [O II] 3727 A emission line is a
knot displaced from the
star by about 1.6 arcsec, indicative of a recent collimated ejection event. [D75] 141 is a M6 III red giant, with weak Balmer-series emission. Both
stars show a blue excess, and GR Cyg was detected in the near-UV by the GALEX spacecraft. These data establish both
stars as new symbiotic binaries, containing a late-type red giant and a hot companion accreting from its stellar wind. We speculate that the double rings surrounding GR Cyg were ejected during helium-shell thermal pulses (or conceivably from recurring nova outbursts), while the nebula around [D75] 141 may be the result of a collision of the symbiotic
star's ejecta with an interstellar cloud. Our accidental discoveries of these two binaries because they are surrounded by faint nebulae supports the view that there is a significant population of "missing" symbiotic
stars yet to be discovered.
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All authors Howard E. Bond, Calvin Carter, Sven E. Eklund, Peter Goodhew, Ulisse Munari, Jonathan Talbot, Gregory R. Zeimann
Astrophysics of Galaxies
Two sets of potential-density basis pairs for the study of radial perturbations in collisionless spherical stellar systems
E. V. Polyachenko and I. G. Shukhman
The Kalnajs
matrix method is a widely used framework for studying the global linear stability and possible Landau damping of collisionless stellar systems. However, for radial perturbations ($l=0$) in three-dimensional spherical models with infinite boundaries, standard biorthogonal sets such as the Clutton-Brock basis often converge slowly. This stems from a physical constraint: mass-conserving radial modes force the perturbed potential to decay faster than a point mass at infinity, whereas individual Clutton-Brock elements carry a fictitious net mass and decay only as $\mathcal{O}(1/r)$, producing unphysical asymptotic tails. We construct two new families of potential-density basis pairs that are free of these tails by construction. The first modifies the Clutton-Brock set: a specific linear combination of adjacent elements analytically cancels the leading $\mathcal{O}(1/r)$ term, giving potentials that decay as $\mathcal{O}(1/r^3)$ and densities as $\mathcal{O}(1/r^5)$. This breaks strict biorthogonality but yields a compact tridiagonal Gram
matrix that enters the response equation at negligible additional cost. The second family is built from Jacobi
polynomials that embed the required $\mathcal{O}(1/r^2)$ potential decay directly into their construction while retaining strict diagonal biorthogonality. Numerical tests demonstrate convergence that is uniform in radius for both expansions: the truncation error decreases exponentially when the asymptotic tail of the expanded potential matches the parity of the basis elements, and algebraically otherwise. Both bases reduce the dimension of the response
matrix required for a given accuracy and are suited to studying radial perturbations in open stellar systems.
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Astrophysics of Galaxies · Cross-listed from astro-ph.IM
Morphology of Radio Sources in Representation Space
Nicolas Baron Perez, Marcus Brüggen and Luisa Lucie-Smith
Understanding
radio source morphologies and their classification remains challenging. We previously developed a deep clustering method based on self-supervised learning to classify a subsample of
radio sources from the LOFAR Two-meter Sky Survey DR2. This yielded a labelled subset used to fine-tune an ensemble of classifiers. We aim to identify rare morphological classes in a subsample of LoTSS-DR3, which contains > 13 million sources, beyond the 12 classes previously recognised in the DR2 sample. We further aim to characterise the resulting class distribution. We applied the classifier ensemble to derive class probabilities and representations for our samples. Among DR3 sources with low class probabilities, we searched for new clusters in representation space. Moreover, we use these clusters as centroids to classify the low-probability subset. We found that 88% of the sources fall into clearly separated clusters in representation space, coinciding with the DR2 clusters. Within the remaining sources, we identified representatives of six additional morphological classes, including rare morphologies like winged and FR-ambiguous sources. The number of sources in the resulting 18 classes exhibit a strongly skewed distribution, with four dominant classes constituting 69% of the DR3 sample, while rare morphologies account for only a small fraction. The identification of additional morphological classes shows the possibility of open-set recognition with representation learning in an unexplored
dataset. Unlike anomaly detection, which flags individual sources as uncommon, this approach identifies representatives of novel morphological classes, providing a framework for discovering novel source populations. The highly skewed class distribution poses a fundamental challenge for constructing balanced training
datasets and highlights the need for open-set approaches in future observations.
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Astrophysics of Galaxies · Cross-listed from astro-ph.EP
Disk survey in the Serpens star-forming region: Environmental effects in nearby star-forming regions
Simin Tong, Nienke van der Marel, Jonathan P. Williams et al. (+1 more)
The external environment where protoplanetary disks are embedded regulates disk
evolution. External irradiation, which heats and evaporates gas, as well as frequent stellar encounters, which truncate disks, can reduce disk sizes and masses. Disk surveys in nearby
star-forming regions with various environments can help us understand how external environments impact disk
evolution. The Serpens
star-forming region, which is thought to be dense but not highly irradiated by massive
stars, is an ideal laboratory to study the dynamical effects on disk properties. We aim to study how dynamical interactions modify disk dust masses by comparing Serpens with other nearby
star-forming regions through their disk masses and 3D stellar densities. We survey 321 young stellar objects from Class I to III in Serpens using ALMA at 0.25 arcsec. We measure disk dust masses from millimeter observations under the optically thin assumption and recompute the 3D stellar density using Gaia data. We apply the same method to other nearby
star-forming regions for direct comparison with Serpens. The cumulative disk dust mass distribution of Serpens is similar to those of similarly aged nearby
star-forming regions, such as Lupus and Taurus. Along with re-assessment of the 3D stellar density, it suggests that Serpens is not likely to have experienced strong tidal truncation capable of producing lower disk dust masses. We also find that the low disk dust mass tension in Ophiuchus and Corona Australis can be resolved when only disks that have been explicitly identified as members of young (1-2 Myr) sub-clusters are considered. Disks without Gaia identifications, especially in Ophiuchus, are spatially clustered in the 2D projected sky plane and less massive than nearby disks with Gaia identifications, possibly tracing the effects of tidal truncation in denser environments at earlier evolutionary stages.
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All authors Simin Tong, Nienke van der Marel, Jonathan P. Williams, Alexa R. Anderson
Astrophysics of Galaxies
Rapid Growth of Intermediate-Mass Black Holes through Disk-induced Stellar Disruptions
Mengye Wang, Yiqiu Ma, Qingwen Wu et al. (+3 more)
Dense nuclear
star clusters provide unique environments for studying the dynamical interactions between
stars and massive black holes. When an
accretion disk is present, dissipative
star–disk interactions can capture surrounding
stars, drive their inward migration, and ultimately lead to disk-induced tidal disruption events\,(dTDEs). The long-term feeding rate from this process, however, cannot be inferred from single-orbit migration estimates alone, as it depends on the coupled
evolution of disk capture, collisional relaxation, stellar depletion and replenishment, and physical mergers within the
star cluster. In this work, we use high-performance direct $N$-body simulations combined with analytic prescriptions for
star–disk interactions to follow this coupled
evolution for intermediate-mass black holes\,(IMBHs) with
accretion disks embedded in dense stellar clusters. The simulations track the formation of the stellar cusp, the capture of
stars by repeated disk crossings, their subsequent orbital damping and migration, and their eventual consumption by the central IMBH. We find that dTDEs can sustain stellar mass supply rates of $\sim10^{-3}\,M_\odot \,\mathrm{yr}^{-1}$, which exceeds the Eddington-limited gas
accretion rate for IMBHs with $M_\bullet<10^5\,M_\odot$. These results identify dTDEs as an efficient stellar feeding channel for IMBHs in gas-rich dense stellar systems. As one possible application, this mechanism may help transform $\sim10^3\,M_\odot$ IMBHs into more massive black-hole seeds, provided that compact stellar clusters and
accretion disks persist for $>30$ Myr.
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All authors Mengye Wang, Yiqiu Ma, Qingwen Wu, Boyuan Liu, Zijian Wang, Zhili Wang
Astrophysics of Galaxies · Cross-listed from astro-ph.CO
Prospects for probing dark matter with filamentary 21cm emission
Yizhou Liu, Yingjie Jing, Haoran Shi et al. (+1 more)
The
cosmic web contains most of the matter in the Universe, and its filamentary structure is closely related to the properties of dark matter. Compared with the cold dark matter (CDM) model, warm dark matter (WDM) suppresses the formation of low-mass
halos and produces smoother
cosmic filaments. In this work, we explore whether filamentary 21cm emission can be used to distinguish between these two dark matter models at $z=4$ and $2.5$. We generate intrinsic 21cm brightness temperature maps from cosmological hydrodynamical simulations and produce mock observations by convolving them with Gaussian beams of different angular resolutions. We then compare the predicted filament signals with the expected sensitivities of SKA1-Low and SKA2-Low. We find that the intrinsic 21cm emission clearly reflects the different filament morphologies in the CDM and WDM models, particularly at $z=4$. However, these differences rapidly disappear as the beam size increases, especially for beam sizes larger than 6 arcsec. Although larger beams improve the observational sensitivity, they also erase the small-scale structures that encode the dark matter information. As a result, neither SKA1-Low nor the planned SKA2-Low can directly resolve individual filaments with sufficient sensitivity to distinguish between the two models. We therefore conclude that direct imaging of
cosmic filaments and constraining dark matter through their morphology are unlikely to be feasible with current and planned SKA-Low facilities.
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All authors Yizhou Liu, Yingjie Jing, Haoran Shi, Huijie Hu
Astrophysics of Galaxies
C3PO: A Ly{\alpha} Emitting Galaxy at $z \sim 9$
Weida Hu, Casey Papovich, Taylor A. Hutchison et al. (+6 more)
We present deep, $>10$ hr, JWST NIRSpec G140M and G395M observations of a previously known
galaxy C3PO-8447 at $z=8.99781$. Our new NIRSpec data from the Carbon-3 plus Oxygen (C3PO) survey detect Ly$\alpha$ emission with an escape fraction of $1.5\pm0.3\%$ and a velocity offset of $210\pm80$ km s$^{-1}$, making C3PO-8447 the third Ly$\alpha$ emitting
galaxy confirmed at $z\gtrsim 9$. The
galaxy has a low stellar mass of $2.2\pm0.1\times 10^7\ M_\odot$, a young stellar age of $1.6\pm0.2$ Myr, and a low oxygen abundance of $12+\log(\mathrm{O/H}) = 7.50\pm0.08$. UV diagnostic diagrams incorporating the C IV, O III], and C III] emission lines indicate that the ionization of C3PO-8447 is dominated by the recent starburst. The low Ly$\alpha$ escape fraction of C3PO-8447 implies that C3PO-8447 resides in a small ionized bubble with radius $R \sim 0.07$ to 0.20 pMpc, which can be produced by C3PO-8447 alone. We find no evidence for either a large-scale
galaxy overdensity around C3PO-8447 or a significant contribution from nearby
galaxies to its ionizing
photon budget. Taken together, these results suggest that C3PO-8447 likely represents an ionized bubble powered by a single low-mass, vigorously
star-forming
galaxy during the early stages of
cosmic reionization.
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All authors Weida Hu, Casey Papovich, Taylor A. Hutchison, Rebecca L. Larson, Pablo Arrabal Haro, Steven L. Finkelstein, Nikko J. Cleri, Lu Shen, Jiayang Yang
Astrophysics of Galaxies · Cross-listed from astro-ph.EP
Trans-Neptunian Object dynamics even better explained by a stellar flyby after 4.5 Gyr of evolution
Susanne Pfalzner, Frank W. Wagner and Marco Bischoff
The Trans-Neptunian objects (TNOs) formed together with the
planets from a flat disc of gas and dust but now orbit the Sun mostly on inclined, eccentric orbits. One explanation for the TNOs' orbits is a close flyby of another
star. One with a mass of $M_p =$0.8 Msun at $q_p =$ 110 au and $i_p =$70{\deg} fits the observations. However, such close encounters were more frequent when the Sun was young and still part of its birth cluster. Assuming that the flyby happened then, we use numerical $N$-body simulations to model how the TNOs' orbits changed due to interactions with the
planets over the 4.56 Gyr since the Sun formed. We find that the cold Kuiper belt region lost about 80% and the hot Kuiper belt population about 40% of its initial population. About 7% –8% of the TNOs were injected into the
planet region, but almost all (99%) were ejected afterwards. By contrast, the orbital parameters of distant Sedna-like objects ($q >$60 au) remained basically unchanged. Surprisingly, in sum, these changes improve the fit to the observed TNO population even more, strengthening the argument for a close flyby to the Solar System. The remaining differences concern the location of the cold population and the inclination distribution of the Sedna population. We discuss possible reasons and steps to resolve these issues.
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Astrophysics of Galaxies
Bright star-forming galaxies naturally forming at z>10 in the Shark semi-analytic model
Claudia D.P. Lagos, Angel Chandro-Gomez, Chris Power et al. (+1 more)
The James Webb Space
Telescope (JWST) has unveiled the existence of numerous z>10 bright ultraviolet (UV)
galaxies, potentially challenging
galaxy formation models in a Lambda Cold Dark Matter (LCDM) universe. Modifications to
star formation and stellar feedback models have been suggested to alleviate the tension. However, the fundamental challenge is to design a
galaxy formation model that simultaneously reproduces observations from z=0 to those at the highest
redshifts. Here, we present predictions from the Shark semi-analytic model of
galaxy formation, which is tuned to reproduce the z=0 universe. We show that the same model is capable of reproducing the current UV luminosity function constraints even up to z=17 without the need to invoke variations in the baryon physics model. This model is also capable of reproducing reasonably well the stellar mass function
evolution from z=0 to z=10 and the
cosmic star formation rate (SFR) density at 0<z<15, again with the same baryon physics and parameters. The key to the success of Shark is the triggering of starbursts by violent disk instabilities included in the model, which leads to an increase in the variance of the UV luminosity with increasing
halo mass at z>10. We demonstrate that without this mechanism,
galaxies are not bursty enough in the model to reproduce the observations at z>10.
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All authors Claudia D.P. Lagos, Angel Chandro-Gomez, Chris Power, Aaron S.G. Robotham
Astrophysics of Galaxies
Magnetic Fields in Massive Star-forming Regions (MagMaR). IX. Radiative Torque Alignment and Disruption in NGC6334I
Vineet Rawat, Thiem Hoang, Patricio Sanhueza et al. (+18 more)
Intense radiation from high-mass
stars is expected to significantly affect dust grain
alignment and
evolution through RAdiative Torques (RATs). We investigate this effect in a massive
star-forming region, NGC6334I, using 1.2 mm dust continuum polarization observations from the Atacama Large Millimeter/submillimeter Array. The polarization fraction spans from $\lesssim1\%$ to $\sim10\%$ and decreases with increasing column density, remaining below $2\%$ in dense cores despite high temperatures ($\sim100$ K), where efficient grain
alignment by RATs is expected. We investigate how grain
alignment, grain growth, grain disruption, B-field tangling, and local physical conditions affect the polarization properties of MM1, MM2, MM3, and their surroundings. Polarization angle dispersion shows that B-field tangling contributes to depolarization at moderate densities but cannot fully explain the lowest polarization fractions. Using RAT-based grain
alignment and polarization modeling, we find that reduced
alignment efficiency and high optical depth reproduce the low polarization in the densest regions. MM2 shows evidence of grain growth, with maximum grain sizes $a_{\max}\sim0.35-1.0~\mu$m, while MM1 exhibits smaller values of $\sim0.35-0.50~\mu$m. Accounting for optical depth increases the inferred grain sizes in MM1 to $\sim1.0-2.0~\mu$m. Analytical estimates of radiative torque disruption from the intense outburst suggest that micron-sized grains in high-temperature, moderate-density regions can fragment into submicron grains. Alternatively, high optical depth may also explain the low polarization in the densest regions even in the presence of micron-sized grains. Incorporating the B-field inclination effect indicates a transition from predominantly plane-of-sky fields at low densities to more line-of-sight-aligned configurations at high densities.
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All authors Vineet Rawat, Thiem Hoang, Patricio Sanhueza, Ian W. Stephens, Manuel Fernández López, Paulo Cortés, Jihye Hwang, Junhao Liu, Kaho Morii, Josep Miquel Girart, Ji-Hyun Kang, Yu Cheng, Shanghuo Li, Luis A. Zapata, Eun Jung Chung, Fernando A. Olguin, Huei-Ru Vivien Chen, Piyali Saha, Chakali Eswaraiah, Qizhou Zhang, O.R. Jadhav
Astrophysics of Galaxies
Constraints on mu-variations from the methanol CH3OH thermal lines in the Galaxy at galactocentric distances of 1.5 < D_GC < 13 kpc
A. I. Shtein, J. S. Vorotyntseva and S. A. Levshakov
In this study, constraints are set on hypothetical variations of the fundamental physical constant mu = m_e/m_p - the electron-to-
proton mass ratio - based on thermal emission lines of E-methanol (CH3OH) in the 216-220 GHz frequency range. Molecular spectra toward seven massive clouds located across a wide range of galactocentric distances (1.5 < D_GC < 13 kpc) have been analyzed. The obtained weighted mean value <Delta mu/mu> = (0.5+/-0.5)*10^(-7) does not indicate statistically significant changes in mu at the 1 sigma confidence level of 5*10^(-8), which is in good agreement with previously established upper limits in a number of molecular clouds in the Galactic disk.
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Astrophysics of Galaxies
Search for intranight optical variability in a large sample of intermediate-mass black holes
Himanshu Sharma, Gopal-Krishna, Vibhore Negi et al. (+3 more)
Using the extensive archival database of the Zwicky Transient Facility (ZTF) survey, we have investigated intranight optical variability (INOV) in a large sample of low-mass active galactic
nuclei (LMAGN) powered by intermediate-mass black holes (IMBHs). After applying a sequence of well-motivated selection filters, we constructed an unbiased, representative sample of 62 IMBHs for which $r$-band intranight photometric sequences are available in the ZTF database, yielding 167 sessions with a minimum duration of 2 h. By performing aperture photometry on the sequence of exposures in each session, we derived differential light curves (DLCs) of the target LMAGN relative to two carefully selected non-varying comparison
stars monitored simultaneously with the LMAGN in the same exposure sequence. Application of the widely used test based on $F$-statistics to all these DLCs revealed no case of statistically significant INOV. We discuss this result for the present large sample of LMAGN in the context of an earlier report of INOV detections in another, albeit much smaller and differently selected, sample of LMAGN that had been monitored in targeted observations.
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All authors Himanshu Sharma, Gopal-Krishna, Vibhore Negi, Hum Chand, Krishan Chand, Anshul Kumar Sharma
Astrophysics of Galaxies
Evolution of Virial Clouds - II: From the Formation of First Stars up to their Explosion
Noraiz Tahir, Asghar Qadir, Francesco De Paolis et al. (+1 more)
The existence of cold gas and dust clouds close to the
cosmic microwave background (CMB) temperature was proposed as a potential repository for a significant fraction of the missing baryons in galactic
halos. While the
evolution of the virial clouds from the last scattering surface (LSS) ($z=1100$) up to the formation of Population III (Pop III)
stars ($z=48$) was studied in [N. Tahir, A. Qadir, M. Sakhi, & F. De Paolis, The Euro. Phys. Jour. C 81, 827 (2021)] (Paper I), the subsequent
evolution during the epoch of the first
stars remained unexplored. In the present work, we investigate the second evolutionary phase of the virial clouds, covering the
redshift range $48 \gtrsim z \gtrsim 10$. We develop a comprehensive model incorporating the coupled thermal, chemical, and dynamical
evolution of the cloud, including CMB heating, adiabatic compression due to gravitational contraction, H$_2$ and metal-line cooling, and feedback from Pop III
supernovae. Solving the coupled ordinary differential equations (ODE) numerically, we find that the cloud cools monotonically from $137$~K to $41.5$~K, contracts from $120$~pc to $89.8$~pc, and becomes enriched in metals and molecular hydrogen, while the cooling rate dominates the heating rate throughout the
evolution.
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All authors Noraiz Tahir, Asghar Qadir, Francesco De Paolis, Noor Fatima
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
NGC 1901: A new benchmark cluster for gyrochronology in the TESS Southern continuous viewing zone
Mara Bernizzoni, Timothy R. Bedding, Prasad Mani et al. (+5 more)
We use Gaia DR3 astrometry and TESS time-series photometry to study NGC 1901, a sparse open cluster in the TESS Southern continuous viewing zone, that has been neglected due to its proximity on the sky to the Large Magellanic Cloud. We refine its membership list and measure rotation periods for 32 high-confidence rotating
stars. By applying the gyro-interp empirical model, we calculate a gyrochronal age of 830 $\pm$ 50 Myr. Because NGC 1901 possesses a sub-solar
metallicity of [Fe/H]$\approx -0.11$, its excellent agreement with empirical models suggests that temperature-period relations mitigate
metallicity effects for Sun-like
stars. Our results place NGC 1901 in the gap between the
benchmark open clusters Praesepe (670 Myr) and NGC 6811 (1 Gyr). We find that the rotation sequence exhibits significant
spin-down stalling in late K dwarfs, supporting models of core–envelope recoupling. Furthermore, our findings provide constraints for the cluster's structural
evolution, including its recently identified tidal tail and corona. This study establishes NGC 1901 as a new
benchmark for calibrating the next generation of gyrochronal models.
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All authors Mara Bernizzoni, Timothy R. Bedding, Prasad Mani, Luke G. Bouma, Courtney L. Crawford, Jason Lee Curtis, Benjamin T. Montet, Samir Nepal
Astrophysics of Galaxies
Turbulent gas-rich discs at high redshift: the origin of early massive stellar bars
Joss Bland-Hawthorn, Thor Tepper-Garcia, Chris Hamilton et al. (+4 more)
Recent observations combining the power of ALMA and JWST have revealed large ($3-7$ kpc), massive ($3-10\times10^{10}\,\mathrm{M}_\odot$) stellar bars at $z=4-5$ when the Universe was only 1.2-1.6 Gyr old. At this early epoch, the host
galaxy was baryon-dominated (typically 75% gas, 25%
stars) within the observed extent of the disc ($8-15$ kpc). Using NEXUS $N$-body/hydrodynamic simulations, we show that such bars can form promptly (400$-$800 Myr), provided the disc mass fraction is high ($f_{\rm disc}\gtrsim 70\%$) and the bar is gas-dominated at the time of its formation, consistent with the observations. In this limit, gas-free bars are unstable to vertical bending modes, but a dominant gas component suppresses this instability. Unlike massive bars in the local Universe, these early bars were sites of vigorous
star formation, as we show. Remarkably, for gas-rich models with $f_{\rm gas}\lesssim60\%$, the bars develop X-shaped boxy bulges; at higher gas fractions ($f_{\rm gas}> 60\%$),
diffusion suppresses resonant orbit trapping and the emerging bar collapses within 1 Gyr to form a classical bulge. The bar formation time, length, mass, and $m=2$
Fourier amplitude are all inversely related to $f_{\rm gas}$. We present a simple analytic model for how
stochastic forcing shifts the bar onset time, defined as the time at which the growing bar amplitude reaches a specified threshold.
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All authors Joss Bland-Hawthorn, Thor Tepper-Garcia, Chris Hamilton, Johan M. Villa-Alatorre, Oscar Agertz, Takafumi Tsukui, Ken Freeman
Astrophysics of Galaxies
CLAS+: A large catalog of Changing-Look AGN candidates selected through S-PLUS narrow-band photometry
L. Nakazono, L. L. Oliveira, R. R. Valença et al. (+11 more)
Changing-look active galactic
nuclei (CLAGN) exhibit rapid spectral transitions on timescales of months to years, challenging standard AGN unification models and providing unique insight into
accretion-disk variability and obscuration processes. Despite their scientific importance, systematic searches for CLAGN remain limited by the scarcity of multi-epoch spectroscopy and the difficulty of constructing large samples efficiently. We introduce CLAS+, a catalog constructed by comparing synthetic photometry derived from DESI DR1 and SDSS DR17 spectra with contemporaneous narrow-band imaging from the S-PLUS survey. Applying our pipeline to a parent sample of 98,139
quasars, we select high-confidence CLAGN candidates above a threshold of reduced chi-squared $\chi_r^2 > 15$. We identify 3,554 strong CLAGN candidates, corresponding to 3.6% of the parent sample. This selected fraction is conditional on the adopted criterion and should not be interpreted as an intrinsic CLAGN occurrence rate. Cross-matching with existing CLAGN compilations shows that CLAS+ identifies a large population of previously unreported high-priority candidates (3,481). Among the spectroscopic–photometric comparisons with reliable temporal classification, 40% are classified as photometric turn-on, 41% as intermediate, and 19% as turn-off. We also find an apparent
redshift dependence in the relative fractions, with photometric turn-on candidates becoming more common at higher
redshifts within the CLAS+ selected sample. Therefore, narrow-band photometry provides a powerful and efficient alternative to purely spectroscopic searches for identifying CLAGN candidates at scale. CLAS+ substantially expands the known CLAGN candidate population and provides a valuable target list for future spectroscopic follow-up and time-domain studies with facilities such as Rubin/LSST.
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All authors L. Nakazono, L. L. Oliveira, R. R. Valença, P. Sánchez-Sáez, G. Oliveira-Schwarz, N. M. Cardoso, A. L. O'Mill, S. Panda, E. Telles, R. Demarco, W. Schoenell, T. Ribeiro, A. Kanaan, C. Mendes de Oliveira