Peer Revenue Publish or profit

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Astrophysics Astrophysics of Galaxies

astro-ph.GA Watch Astrophysics of Galaxies

Sunday 27 September

Astrophysics of Galaxies

Barred Galaxies in MaNGA: Stellar Mass Dependence and Black Hole Growth

Chandan Watts and Sudhanshu Barway

This study investigates the role of internal structures, such as stellar bars and active galactic nuclei (AGN), in shaping galaxy evolution using 7,408 galaxies (2,641 barred) from the SDSS-IV MaNGA survey. Our analysis spans a wide stellar mass range, from dwarf to massive galaxies, examining how internal and environmental processes regulate galaxy evolution. Galaxies are categorized by morphology (ellipticals (E), lenticulars (S0s), early-type spirals (ETS), and late-type spirals (LTS)), environment, and the presence of a bar. We find that barred galaxies have higher median specific star formation rate (sSFR) than unbarred galaxies across most stellar mass intervals. This difference varies with host morphology, with LTS and S0 galaxies showing different trends across stellar mass intervals. The environmental trends of barred and unbarred galaxies are broadly similar within the same mass intervals. In AGN hosts, barred Seyferts tend to lie near the star-forming$-$green valley boundary, while barred LINERs preferentially occupy the green valley. We further examine the relation between stellar bars and black hole mass and find that barred galaxies host systematically lower black hole masses than unbarred galaxies, with environmental effects appearing to play a secondary role in shaping these differences. A multivariate regression analysis also shows that the positive bar$-$sSFR association remains statistically significant for star-forming galaxies after accounting for stellar mass, local density, AGN activity, and morphology. Our results highlight the interconnected roles of stellar bars, stellar mass, morphology, and environment in shaping galaxy star formation, providing new insights into the role of stellar bars in galaxy evolution.
Read the full abstract

Astrophysics of Galaxies

CHANG-ES XLII: Cosmic-Ray Electron Transport and the Spatially Resolved Radio-SFR Relation in Edge-on Galaxies

Jianghui Xu, Volker Heesen, Jiang-Tao Li et al. (+6 more)

Radio continuum emission traces star formation in galaxies, but cosmic-ray electron (CRE) propagation between the disk and halo complicates this connection. We present a wide-band, spatially resolved analysis of 19 nearby edge-on galaxies, combining LOFAR observations at 144 MHz with CHANG-ES VLA imaging at 1.575, 3.0, and 6.0 GHz, and hybrid H$\alpha$+22 $\mu$m star formation rate (SFR) maps. All maps are convolved to a common 2.1 kpc resolution for pixel-by-pixel analysis of the nonthermal spectral index $\alpha_{\mathrm{nth}}$ and the SFR surface density $\Sigma_{\mathrm{SFR}}$. All 19 galaxies exhibit statistically significant nonthermal spectral flattening with increasing $\Sigma_{\mathrm{SFR}}$, with a sample median slope of $0.19_{-0.03}^{+0.09}$ that traces the contrast between CRE injection in the star-forming disk and cooling in the halo. The galaxy-to-galaxy scatter in this slope shows no dependence on global galaxy properties and instead appears to be modulated by the local dynamical environment, with the largest $\alpha_{\mathrm{nth}}$-$\Sigma_{\mathrm{SFR}}$ slopes appearing in tidally perturbed systems. The resolved radio-SFR slope steepens from 0.57 at 144 MHz to 0.95 at 6 GHz, approaching linearity at high frequencies. This trend is consistent with energy-dependent CRE cooling and transport, with the deviation from linearity most pronounced at low frequencies, where the edge-on line of sight blends midplane and halo CRE populations. These results are robust against thermal contamination, beam smearing, and spectral curvature. Together, our analysis establishes $\alpha_{\mathrm{nth}}$ as an observational probe of projected disk-to-halo CRE transport in edge-on galaxies and quantifies how this transport reshapes the frequency dependence of resolved radio-SFR calibrations.
Read the full abstract

All authors Jianghui Xu, Volker Heesen, Jiang-Tao Li, Guilin Liu, Rainer Beck, Li-Yuan Lu, Yang Yang, Jayanne English, Shengtao Wang

Saturday 26 September

Astrophysics of Galaxies

Cool Embeddings: Predicting Galaxy Cluster Cooling Times in IllustrisTNG and TNG-Cluster with AstroCLIP

Rawan Karam, Carter Lee Rhea, Julie Hlavacek-Larrondo et al. (+4 more)

Foundation models trained on optical astronomical data have not previously been applied to X-ray cluster thermodynamics. We show that embeddings from AstroCLIP, a contrastive vision-language model trained on optical galaxy images and spectra, retain physically meaningful structure when applied to mock Chandra X-ray images of simulated galaxy clusters - a significant shift in observational modality and physical scale. We target the central cooling time ($t_{\mathrm{cool},0}$) of the intracluster medium, a key diagnostic of cluster thermodynamics traditionally requiring X-ray spectroscopy. We present a machine learning framework that predicts $t_{\mathrm{cool},0}$ directly from X-ray images, applied to 711 projections from TNG300 and 993 from TNG-Cluster from the IllustrisTNG simulations. AstroCLIP embeddings form a structured latent space in which clusters with similar thermodynamic properties are naturally grouped, with no equivalent separation by halo mass. Building on this, we introduce a dot-product $k$-nearest neighbour attention model that retrieves similar clusters from the training set and adaptively reweights their cooling times. This model achieves root-mean-square errors of 0.24 (TNG300) and 0.23 (TNG-Cluster) in $\log(t_{\mathrm{cool},0})$, and demonstrates strong out-of-distribution generalisation, outperforming a fine-tuned convolutional neural network trained on raw images (RMSE 0.50 versus 0.73). These results demonstrate that pretrained foundation model embeddings transfer across astrophysical domains and encode thermodynamic information sufficient for inference of cluster cooling properties - offering a scalable path toward cool-core characterisation in all-sky surveys such as eROSITA.
Read the full abstract

All authors Rawan Karam, Carter Lee Rhea, Julie Hlavacek-Larrondo, Laurence Perreault-Levasseur, Marine Prunier, Adam Alexandre, Hyunseop Choi

Astrophysics of Galaxies · Cross-listed from astro-ph.HE

Constraints on Supermassive Black Hole Binaries from the Lack of Resolvable Sources in the NANOGrav 15-yr Dataset

Emiko C. Gardiner, Kayhan Gültekin, Philippe Turgeon et al. (+116 more)

Pulsar timing arrays (PTAs) have found evidence of a gravitational wave background (GWB) consistent with a population of supermassive black hole binaries (SMBHBs), but have not yet resolved a continuous wave (CW) from an individual binary. We present the first SMBHB population constraints incorporating PTA upper limits on CWs, based on the NANOGrav 15-year (NG15) data. Using semi-analytic models to generate simulated populations, we calculate each sample's GWB likelihood by free spectral comparison and CW nondetection (nCW) likelihoods by (1) mapping each realization's highest CW signal-to-noise ratio (S/N) to a detection probability and (2) counting the fraction of realizations without a binary close enough that NG15 would have detected it. CW nondetection favors populations in which many lower-mass sources, rather than a few ultramassive ones, dominate the GWB. This information is complementary to that provided by the GWB amplitude, breaking the degeneracy between the masses and number of binaries required to reproduce the observed spectrum. Relative to GWB-only constraints, the joint posteriors favor higher galaxy merger rates, lower $M_\mathrm{BH}$-$M_\mathrm{bulge}$ scatter, shorter binary lifetimes, and steeper small-separation hardening. The most detectable sources in the S/N-weighted joint posterior have chirp masses $\sim 10^{9.6} M_\odot$, luminosity distances $\sim$1300 Mpc, and frequencies $\sim$6 nHz, while the nCW-only constraints favor lower frequencies, coinciding with the NG15 4 nHz candidate. These constraints will tighten if CW nondetection continues.
Read the full abstract

All authors Emiko C. Gardiner, Kayhan Gültekin, Philippe Turgeon, Bence Bécsy, Laura Blecha, Nikita Agarwal, Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, Anjana Ashok, Jeremy G. Baier, Paul T. Baker, Adam Brazier, Paul R. Brook, Sarah Burke-Spolaor, Rand Burnette, Robin Case, J. Andrew Casey-Clyde, Maria Charisi, Shami Chatterjee, Tyler Cohen, James M. Cordes, Neil J. Cornish, Fronefield Crawford, H. Thankful Cromartie, Kathryn Crowter, Megan E. DeCesar, Paul B. Demorest, Heling Deng, Lankeswar Dey, Timothy Dolch, Graham M. Doskoch, Elizabeth C. Ferrara, William Fiore, Emmanuel Fonseca, Gabriel E. Freedman, Nate Garver-Daniels, Peter A. Gentile, Kyle A. Gersbach, Joseph Glaser, Deborah C. Good, Aiden Gundersen, C. J. Harris, Jeffrey S. Hazboun, Ross J. Jennings, Aaron D. Johnson, Megan L. Jones, David L. Kaplan, Anala Kavumkandathil Sreekumar, Luke Zoltan Kelley, Matthew Kerr, Joey S. Key, Nima Laal, Michael T. Lam, William G. Lamb, Bjorn Larsen, T. Joseph W. Lazio, Natalia Lewandowska, Tingting Liu, Duncan R. Lorimer, Jing Luo, Ryan S. Lynch, Chung-Pei Ma, Dustin R. Madison, Ashley Martsen, Cayenne Matt, Alexander McEwen, James W. McKee, Maura A. McLaughlin, Natasha McMann, Bradley W. Meyers, Patrick M. Meyers, Matthew T. Miles, Chiara M. F. Mingarelli, Andrea Mitridate, Cherry Ng, David J. Nice, Shania A. Nichols, Stella Koch Ocker, Daniel J. Oliver, Ken D. Olum, Timothy T. Pennucci, Benetge B. P. Perera, Polina Petrov, Nihan S. Pol, Henri A. Radovan, Scott M. Ransom, Paul S. Ray, Joseph D. Romano, Jessie C. Runnoe, Alexander Saffer, Shashwat C. Sardesai, Ann Schmiedekamp, Carl Schmiedekamp, Kai Schmitz, Levi Schult, Brent J. Shapiro-Albert, Xavier Siemens, Joseph Simon, Sophia V. Sosa Fiscella, Ingrid H. Stairs, Daniel R. Stinebring, Kevin Stovall, Abhimanyu Susobhanan, Joseph K. Swiggum, Jacob Taylor, Stephen R. Taylor, Mercedes S. Thompson, Jacob E. Turner, Michele Vallisneri, Rutger van Haasteren, Joris P. W. Verbiest, Sarah J. Vigeland, Haley M. Wahl, Kevin P. Wilson, Caitlin A. Witt, David Wright, Olivia Young

Astrophysics of Galaxies

The Physical Origins of Scatter in the Dust Attenuation Scaling Relation of Star-Forming Galaxies: Star–Dust Geometry

Zongfei Lyu, Xian Zhong Zheng, Zhizheng Pan et al. (+11 more)

Characterising the physical drivers of dust attenuation in star-forming galaxies (SFGs) is essential for interpreting their spectral energy distributions and star formation histories. The infrared excess (IRX$\equiv$$L_{\rm IR}/L_{\rm UV}$) follows a universal scaling relation with metallicity, star formation rate, galaxy size, and inclination. However, the origin of the scatter around this relation remains poorly understood. We revisit this relation using $\sim$32,000 local SFGs from SDSS, GALEX, and WISE, and investigate why some galaxies deviate systematically from the best-fit relation. We find that the deviations are systematically linked to UV luminosity. UV-faint SFGs ($\log(L_{\rm UV}/{\rm L}_\odot)\le 9$) exhibit a median IRX excess of +0.23 dex, while UV-bright SFGs ($\log(L_{\rm UV}/{\rm L}_\odot)\ge 10$) show a median deficit of $-$0.20 dex relative to the relation defined by the dominant UV-intermediate population (86.38 percent of the sample). These offsets are not driven by metallicity, total infrared luminosity, or specific star formation rate. Instead, the deviations are closely linked to systematic differences in star–dust geometry. UV-faint SFGs are compact (median $R_{\rm e} = 2.90$ kpc) and preferentially viewed edge-on (median $b/a = 0.41$), leading to high effective dust column densities along the line of sight. UV-bright SFGs are extended (median $R_{\rm e} = 5.99$ kpc) and preferentially viewed face-on (median $b/a = 0.74$), allowing UV photons to escape efficiently. Galaxies with significant bulge components ($B/T > 0.4$) populate the envelope of the relation, exhibiting larger scatter. We conclude that the scatter in the IRX relation can be largely explained by variations in the three-dimensional star–dust geometry, with UV luminosity acting as an effective tracer of these geometric and physical differences.
Read the full abstract

All authors Zongfei Lyu, Xian Zhong Zheng, Zhizheng Pan, Antonios Katsianis, Stijn Wuyts, Haiguang Xu, Pedro Cataldi, Wenhao Liu, Man Qiao, Dong Dong Shi, Yuheng Zhang, Shuang Liu, Run Wen, Chao Yang

Astrophysics of Galaxies

H-alpha Star Formation Rates of the SHIELD Dwarf Galaxies

Madeline Shepley, David G. Gormanous, John J. Salzer et al. (+9 more)

The Survey of HI in Extremely Low-mass Dwarfs (SHIELD) galaxy sample is an HI-selected catalog of galaxies that occupy the extreme low-mass end of the HI mass function. Our team is carrying out a comprehensive multi-wavelength observational program targeting these gas-rich, star-forming dwarf galaxies. The current paper presents H-alpha narrowband observations of the full SHIELD sample. We detect 55 of the 82 galaxies (67%) with nebular H-alpha emission, and infer sensitive upper limits to the H-alpha fluxes for the 27 non-detections. We derive H-alpha luminosities and star formation rates (SFRs), or upper limits, for all 82 SHIELD galaxies. We also present, for the first time, deep broadband and continuum-subtracted H-alpha images plus a summary of the properties for the entire sample. Our analysis of the H-alpha data re-affirms previous results which show that at low levels of star formation (log(SFR_{H-alpha}) < -2.5), H-alpha becomes an increasingly poor tracer of the recent average SFR as measured by far-UV (FUV) luminosities. However, we show that this effect is not strictly correlated with the mass of the galaxy. Some very low-mass SHIELD galaxies with higher H-alpha-based SFRs show good agreement with SFR_{FUV}. The SHIELD galaxies show no correlation between H-alpha SFR and gas mass fraction, but reveal a modest correlation between H-alpha specific SFR and gas mass fraction. Overall, the star formation efficiency exhibited by the SHIELD dwarfs is rather low, despite the gas-rich nature of the sample (68% have M_{gas} > M_{stellar}).
Read the full abstract

All authors Madeline Shepley, David G. Gormanous, John J. Salzer, Nathalie Haurberg, Steven Janowiecki, John M. Cannon, Elizabeth A. K. Adams, Martha P. Haynes, Alec S. Hirschauer, Kristen B. W. McQuinn, Katherine L. Rhode, Evan D. Skillman

Astrophysics of Galaxies

Tracing Winds through the Fog: A Comprehensive Survey of LMC's Galactic Outflows with ULLYSES

Suraj Poudel, April Horton, Kathleen A. Barger et al. (+21 more)

We investigate nearside stellar-driven outflows from the Large Magellanic Cloud (LMC) using UV absorption-line spectroscopy of 170 OB stars, complemented by HI 21-cm emission and H$_{\alpha}$ emission. Using Voigt-profile fitting and AOD analysis of SiII, OI, and SII transitions, we map the velocity-dependent structure of foreground gas. The SiII column densities for the Voigt-fitted components decline smoothly from the LMC disk and reach a minimum at $v_{\rm LMCSR} \approx -100$ to $-200~{km~s^{-1}}$, marking the transition from a denser, slower wind to more diffuse high-velocity material. Comparisons with local star-formation rate surface densities reveal a modest positive correlation for the slower wind component, linking it to recent massive-stellar feedback. Photoionization modeling of 13 absorbers in the $+100\lesssim v_{\rm LSR} \lesssim +150~{km~s^{-1}}$ range reveals wide diversity in metallicity, dust depletion, and ionization conditions, consistent with multiple possible origins. While a substantial fraction of this predominately ionized gas is consistent with the high-velocity extension of the LMC wind, part of it may arise from contamination by Milky Way (MW) high-velocity clouds (HVCs) and Magellanic circumgalactic medium (CGM). We estimate a nearside cool-gas outflow mass of ${\sim}1.8\times10^{7}\,M_{\odot}$, implying $\dot{M}_{\rm out}\approx0.15$-$0.33\,M_{\odot}\,\mathrm{yr^{-1}}$ and a mass-loading factor of $\eta\approx0.6$-1.3. On regional scales, 30 Doradus contributes $\sim10\%$ and N11 contributes $\sim3\%$ of the total outflow mass, while the trailing side contains more wind material than the leading side, consistent with ram-pressure stripping. These results provide the comprehensive kinematic and physical characterization of how stellar feedback, galactic environment, and foreground contamination shape the multiphase wind emerging from the LMC.
Read the full abstract

All authors Suraj Poudel, April Horton, Kathleen A. Barger, Frances H. Cashman, Jo Vazquez, Andrew J. Fox, Nicolas Lehner, J. Christopher Howk, Scott Lucchini, Dhanesh Krishnarao, Sabra Catalano, Anders Ripley, Wanyan Yuan, Natalie Van Tol, Citlali Alcala, Jordan Elliott, N. M. McClure Griffiths, Elena D'Onghia, Jason Tumlinson, Ananya Goon Tuli, Jacco Th. van Loon, Julia Roman-Duval, Yik Ki Ma, Callum Lynn

Friday 25 September

Astrophysics of Galaxies

The AURORA Survey: Determining the Production Mechanism for OI $\mathbf{\lambda 8449}$ Emission in Star-forming Galaxies at Cosmic Noon

Leonardo Clarke, Alice E. Shapley, Zhiwei Shao et al. (+11 more)

We analyze deep JWST/NIRSpec observations of 58 star-forming galaxies at $1.3< z <4.8$ in the AURORA survey to investigate the origin of the permitted OI $\lambda 8449$ emission feature. Based on the detection of OI $\lambda 8449$ in a stack of objects with non-detections, we infer that this feature is ubiquitous among star-forming galaxies at $\sim$0.5% the strength of H$\alpha$. We additionally compare our results with measurements of this line in local HII regions from the CHAOS survey and star-forming galaxies at $z<0.1619$ in the DESI survey, finding a similar strength of OI $\lambda 8449$ relative to H$\alpha$ in these objects. We evaluate four production mechanisms: recombination, collisional excitation, Ly$\beta$ fluorescence, and stellar continuum fluorescence. Of these mechanisms, stellar continuum fluorescence (rather than Ly$\beta$ fluorescence) provides the most compelling explanation for the OI $\lambda 8449$ emission based on the additional detection of the near-infrared OI $\lambda 11290$ and OI $\lambda 13168$ emission lines. Adopting physical conditions derived from a stacked composite spectrum, we make predictions for the contribution of the other mechanisms to OI $\lambda 8449$, determining that recombination, collisional excitation, and Ly$\beta$ fluorescence contribute negligibly to this feature. While a simple HII region model using Cloudy reproduces the average observed OI $\lambda 8449$/H$\alpha$ ratios in the AURORA sample, future works focused on refining model density profiles will be a valuable step in better explaining the near-infrared OI emission-line strengths.
Read the full abstract

All authors Leonardo Clarke, Alice E. Shapley, Zhiwei Shao, Massimo Pascale, Ryan L. Sanders, Naveen A. Reddy, Tucker Jones, Harley Katz, Natalie Lam, Shreya Karthikeyan, Callum T. Donnan, Natascha M. Förster Schreiber, Anthony J. Pahl, Danielle A. Berg

Astrophysics of Galaxies · Cross-listed from astro-ph.CO

SLICE: Unveiling the Multi-Component Merging Core of SPT-CLJ1150-2805 Through Strong-Lensing Mass Modelling

James R. Betts, Benjamin Beauchesne, Mathilde Jauzac et al. (+16 more)

We present a new strong-lensing and X-ray mass model of the merging galaxy cluster SPT-CLJ1150-2805 ($z=0.383$), combining JWST NIRCam, HST, Chandra, and VLT/MUSE data to robustly decompose its collisionless and collisional components. Exploiting JWST, we expand the multiple-image catalogue with 66 new images (30 comprising 6 new systems). Our baseline model uses 118 spectroscopically confirmed images from 20 systems, achieving an image-plane root-mean-square offset of $0.56''$. An expanded model incorporating 31 additional photometric images from 8 additional systems yields a near-identical mass distribution, confirming excellent model stability. We resolve a complex multi-axis post-merger system requiring five cluster-scale dark matter haloes, including a bimodal core with distinct haloes coincident with each brightest cluster galaxy. The remaining mass components are independently supported by kinematics of 291 cluster members ($\sigma_v=1960^{+84}_{-92}$ km s$^{-1}$), which reveal two new galaxy substructures - the northernmost of which we tentatively identify as the baryonic counterpart to our fifth dark matter halo. The cluster is an extraordinarily efficient lens, possessing an effective Einstein radius $\theta_E=42.41^{+0.05}_{-0.04}{''}$ and an enclosed mass $M(<\theta_E)=3.35^{+0.04}_{-0.03}\times10^{14}M_\odot$ for a source at $z_s=2$. For a high-redshift source at $z_s=9$, it produces a magnification cross-section of $A(>10)\simeq0.15$ arcmin$^2$ and $A(>30)\simeq0.020$ arcmin$^2$. This global lensing power surpasses all Hubble Frontier Fields clusters. In a regime where systematic uncertainties between mass models dominate high-redshift magnification errors, the stability of our reconstruction sets this lens apart. This combination of extreme lensing power and a robust mass model establishes SPT-CLJ1150-2805 as a premier cosmic telescope for high-redshift studies.
Read the full abstract

All authors James R. Betts, Benjamin Beauchesne, Mathilde Jauzac, David Lagattuta, Guillaume Mahler, Jean-Paul Kneib, Gavin Leroy, Marceau Limousin, Priyamvada Natarajan, Sameeksha Saini, Keren Sharon, Stephane V. Werner, Catherine Cerny, Isaque Dutra, Dominique Eckert, Alaina Einsig, Michael D. Gladders, Gourav Khullarm, Manon Regamey

Astrophysics of Galaxies

Dynamical Evolution of The Open Clusters Collinder 110 and NGC 2477

Zahra Al, Yüksel Karataş and Forough Rajaei

Using Gaia DR3 photometric and astrometric data, we identified the likely members of the open clusters Collinder 110 and NGC 2477, and derived their astrophysical and dynamical parameters. We obtained reddening values of $E(B-V) = 0.43 \pm 0.05$ and $0.33 \pm 0.04$, and ages of $1.82 \pm 0.10$ Gyr and $1.05 \pm 0.10$ Gyr for Collinder 110 and NGC 2477, respectively. Within the uncertainties, the distances derived from the color-magnitude diagrams ($2.09 \pm 0.06$ and $1.38 \pm 0.04$ kpc) are consistent with those obtained from Gaia DR3 parallaxes ($2.08 \pm 0.31$ and $1.45 \pm 0.11$ kpc). Both clusters exhibit large core and limiting radii. The core radius ($R_c$) of Collinder 110 does not follow the expected decreasing trend with increasing evolutionary parameter ($\log\tau_2$). In addition to losing part of its low-mass stellar content, its relatively large $R_c$ may reflect primordial conditions and/or the presence of a possible stellar-mass black hole. The relatively large $R_c/R_h$ ratios, together with their advanced dynamical evolution ($\log\tau_2 = 1.24$ and $1.34$), indicate that significant two-body relaxation and mass segregation have occurred within their central regions. The small values of $R_h/R_j$ ($0.32$ and $0.16$) suggest that low-mass stars have dynamically redistributed within the comparatively large Jacobi radii under the combined influence of internal and external processes. However, their large $R_t/R_j$ ratios ($1.60$ and $1.23$) imply that both clusters are tidally affected and have likely lost part of their low-mass stellar populations to the Galactic field. Despite these effects, their locations in the third Galactic quadrant, where giant molecular clouds are relatively scarce, may explain their survival to their present ages of $1.82$ and $1.05$ Gyr, respectively.
Read the full abstract

Astrophysics of Galaxies

Quantifying the decline in CO(2-1) intensity around PHANGS-HST star clusters: Constraints on molecular gas dispersal, stellar feedback, and cluster formation efficiency

Hao He, Adam K. Leroy, Erik Rosolowsky et al. (+36 more)

We combine the largest survey of star clusters in nearby galaxies to-date, PHANGS-HST, with maps of molecular gas maps from PHANGS-ALMA to constrain the efficiency of cluster formation and the typical timescales over which clusters become dis-associated from their natal molecular gas. We analyse 29,233 clusters in 36 galaxies using CO maps at 150 pc resolution. For each star cluster with stellar mass $\geq 10^{3.5}$ M$_\odot$, we measure the radial profiles of CO(2-1) integrated intensity and obtain local background-subtracted CO intensity, $I_{\rm CO}^{\rm bkgsub}$, at cluster centre. We group the clusters by age and mass to quantify the dependence of $I_{\rm CO}^{\rm bkgsub}$ and corresponding molecular gas mass, $M_{\rm mol}$, on these cluster properties. To account for the cluster mass ($M_{\rm SC}$) dependence, we also calculate the normalised mass ratio of $(M_{\rm mol}/M_{\rm SC})$. We find that CO intensity varies systematically with cluster age and mass. Clusters that are spatially associated with H$\alpha$ emission exhibit the highest $I_{\rm CO}^{\rm bkgsub}$ of 7.4 K km s$^{-1}$, corresponding to a $M_{\rm mol}/M_{\rm SC}$ ratio of 82 and implying a cluster formation efficiency ($\epsilon_{\rm obs}$) of $\sim 1.2\%$. Young clusters without associated H$\alpha$ emission show lower and age-dependent $I_{\rm CO}^{\rm bkgsub}$ and $M_{\rm mol}/M_{\rm SC}$, decreasing from 1.3 K km s$^{-1}$ and 15 for clusters with age 1-3 Myr, to a level $\approx$ 0 for clusters older than 9–10 Myr. Clusters older than 10 Myr show no statistical excess of CO intensity. We use the clusters with H$\alpha$ association as initial conditions to model the impact of cluster drift and demonstrate that this is unlikely to drive the observed cluster-gas spatial disassociation on short timescales of 4-6 Myr. Instead, early stellar feedback seems likely to be the main driver.
Read the full abstract

All authors Hao He, Adam K. Leroy, Erik Rosolowsky, Janice Lee, Brad Whitmore, David Thilker, Daniel A. Dale, Frank Bigiel, Annie Hughes, Jiayi Sun, Gagandeep Anand, Ashley T. Barnes, Zein Bazzi, Médéric Boquien, Rupali Chandar, Dario Colombo, Sinan Deger, Simthembile Dlamini, Hamid Hassani, Stephan Hannon, Ralf S. Klessen, Simon C.O. Glover, Kathryn Grasha, Ivan Grasimov, Remy Indebetouw, Kirsten Larson, Lukas Neumann, Elias K. Oakes, Hsi-An Pan, Miguel Querejeta, Lise Ramambason, M. Jimena Rodríguez, Sumit K. Sarbadhicary, Eva Schinnerer, Qiushi Tian, Leonardo Úbeda, Antonio Usero, Thomas G. Williams, Jianwen Zhou

Astrophysics of Galaxies

$\textit{N\=ap\=owaw\=a`enakaulua}$: a close quasar pair at cosmic dawn in the Aether survey

Silvia Onorato, Emanuele Paolo Farina, Roberto Decarli et al. (+32 more)

We present the discovery and first characterization of $\textit{N\=ap\=owaw\=a`enakaulua}$: the most compact known quasar pair candidate in the Epoch of Reionization, with a projected separation of only $0.98^{\prime\prime}$ ($\approx 5.56$ pkpc at $z \sim 6.08$) and a velocity offset of $\Delta v \simeq 15 \text{ km s}^{-1}$. Using spectroscopy from JWST/NIRSpec IFU, as part of the $\textit{Aether survey}$, Gemini/GNIRS and GMOS we characterize the continuum and emission line properties of the two quasars, enabling constraints on their black hole masses ($M_{\text{BH}} \simeq 1.5 \times 10^9$ and $4.0 \times 10^8\,M_\odot$), accretion states ($\lambda_{\text{Edd}} \simeq 1.23$ and $1.07$), and systemic redshifts ($z_{\rm sys} \simeq 6.0781$ and $6.0785$). We place this pair in the cosmological context by comparing the chance of occurrence to extrapolations of high-$z$ quasar clustering measurements at larger scales, resulting in a $\sim 2-3$ order of magnitude excess with respect to expectations. This excess hints at an underlying population of merger-triggered quasar pairs at cosmic dawn or to a denser-than-average galactic environment. $\textit{N\=ap\=owaw\=a`enakaulua}$ thus represents a crucial signpost to investigate the mass assembly of the first massive galaxies and black holes.
Read the full abstract

All authors Silvia Onorato, Emanuele Paolo Farina, Roberto Decarli, Klaudia Protušová, Elia Pizzati, Debora Pelliccia, Devin S. Chu, Larry Lindsey Kimura, Leinani Lozi, Emily Peavy, Fabrizio Arrigoni-Battaia, Eduardo Bañados, Aaron J. Barth, Silvia Belladitta, Manuela Bischetti, Sarah E. I. Bosman, Hyunseop Choi, Tiago Costa, Anna-Christina Eilers, Xiaohui Fan, Simona Gallerani, Thomas R. Geballe, Anniek J. Gloudemans, Eunchong Kim, Brian C. Lemaux, Weizhe Liu, Yoshiki Matsuoka, Chiara Mazzucchelli, Atsuko Nitta, Jan-Torge Schindler, Andrew W. Stephens, Hyewon Suh, Fabian Walter, Feige Wang, Jinyi Yang

Astrophysics of Galaxies

Balmer Break Measurements Trace Departures from the Star-Forming Main Sequence at $1<z<4$ with JWST/NIRSpec

Suprabhas Narisetty, Yongda Zhu, Eiichi Egami et al. (+4 more)

We present JWST/NIRSpec PRISM observations of galaxies at $1<z<4$ to study the relation between Balmer-break strength ($D_{\rm Balmer}$) and recent star formation. Using NIRSpec spectra from the JADES Transient Survey in GOODS-S, we measure $D_{\rm Balmer}$ and hydrogen recombination-line equivalent widths, and infer galaxy properties through spectral energy distribution (SED) fitting of the accompanying photometry. We find a clear anti-correlation between $D_{\rm Balmer}$ and the rest-frame equivalent width of H$\alpha$+[\ion{N}{2}], such that galaxies with stronger breaks show weaker nebular emission and lower recent star formation activity. $D_{\rm Balmer}$ also correlates with mass-weighted stellar age, supporting its use as an empirical tracer of evolved stellar populations at these redshifts. Star formation rates inferred from H$\alpha$, Pa$\gamma$, and SED fitting are broadly consistent, with scatter likely driven in part by dust attenuation, line-measurement uncertainties, and the different timescales probed by each indicator. Galaxies with stronger $D_{\rm Balmer}$ also tend to lie further below the star-forming main sequence at fixed stellar mass, indicating that $D_{\rm Balmer}$ is linked to recent suppression of star formation. In contrast, we find only a weak relation between $D_{\rm Balmer}$ and SED-derived dust attenuation, suggesting that dust is not the main driver of the observed trends. These results show that $D_{\rm Balmer}$, combined with recombination-line measurements, is a useful empirical diagnostic of galaxies transitioning away from the star-forming population at cosmic noon.
Read the full abstract

All authors Suprabhas Narisetty, Yongda Zhu, Eiichi Egami, Stefano Carniani, Francesco D'Eugenio, Christa DeCoursey, Christopher N. A. Willmer

Astrophysics of Galaxies

MUSE spectroscopy of the compact dual AGN in the $z=3.273$ radio-loud gravitational lens MG B2016+112

Jianghao Huyan, Júlia M. Sisk-Reynés, Daniel A. Schwartz et al. (+4 more)

Dual active galactic nuclei (AGN) are unique laboratories for studying how galaxy mergers trigger accretion onto supermassive black holes (SMBHs). However, at redshifts $z>1$, only few dual AGN are confirmed at projected separations $\gtrsim$ 1 kpc for the two SMBHs. We present archival MUSE spectroscopy of the three resolved lensed images of the radio-loud system MG B2016+112. At z = 3.273 and at a projected separation of 175 pc, this the most compact confirmed dual AGN at z > 1. We detect Ly$\alpha$, C IV, N V, He II, and C III] emission across images A$--$C after correcting for ISM absorption at $z \sim 0$. We find that the Ly $\alpha$, C IV, N V lines are affected by saturated absorption at $z \sim 3.27$. The He II / C III] emission-line ratios are consistent between images A and B but differ significantly from image C. We fit the C IV emission regions of images A$--$C by allowing for up to two Gaussians and use broad component to place lower limits on their respective SMBH masses: $\gtrsim 2 \times {10}^{7} M_\odot$, $\gtrsim 2.3 \times {10}^{7} M_\odot$, and $\gtrsim 1.5 \times {10}^{7} M_\odot$. Correcting for their strong lensing magnifications suggests Eddington ratios of $\lesssim$ 0.47, 0.51, and 0.04, respectively. Together with previous VLBI and X-ray analyses, our results provide strong, independent spectroscopic evidence that MG B2016+112 hosts two AGN. Our findings motivate deep, spatially resolved near-IR spectroscopy to independently revisit our mass estimates and determine the physical conditions of the host galaxy, which has likely undergone a major merger.
Read the full abstract

All authors Jianghao Huyan, Júlia M. Sisk-Reynés, Daniel A. Schwartz, Varsha P. Kulkarni, Anna Barnacka, Adi Foord, Charlotte A. Eades

Astrophysics of Galaxies · Cross-listed from astro-ph.SR

The Molecular Circumstellar Environments of Red Supergiants in Galactic Open Clusters

Mark A. Siebert, Elvire De Beck, Guillermo Quintana-Lacaci et al. (+4 more)

We aim to expand the sample of RSGs with direct measurements of circumstellar gas through millimeter observations of two of the largest coeval RSG populations in the Galaxy: the open clusters RSGC1 and RSGC2. We present an interferometric molecular line study of 28 RSGs in RSGC1 and RSGC2 with ALMA. The primary targeted emission is CO $J=2-1$ and continuum, with additional thermal and maser SiO lines observed for RSGC2 targets. We measure terminal expansion velocities, systemic velocities, emission-region sizes, and provide updated dust models and luminosities using the new long-wavelength constraints. Finally, we perform 1D radiative transfer modeling of CO rotational-line emission to estimate mass-loss rates. We detect $^{12}$CO toward six RSGs in RSGC2 and five in RSGC1. Except for DFK 52, the spatial distribution of all $^{12}$CO emission is relatively compact or unresolved. The obtained mass-loss rates range from $\log(\dot{M}/M_\odot\,\mathrm{yr}^{-1})=-5.5$ to $-3$, but are highly uncertain due to a lack of stringent constraints on the envelope sizes and temperatures. The lower-limit $\dot{M}$-values we obtain are high compared to standard empirical prescriptions and favor dust models assuming a radiatively driven wind. DFK 49 is a clear outlier: its revised luminosity is the lowest in both clusters, yet it harbors a strong wind with $\dot{M}>10^{-5}\,M_\odot\,\mathrm{yr}^{-1}$. The CO emission regions are much smaller than expected from nearby RSGs and theoretical models, and suggest a unique phase structure for the CSM around RSGs in cluster environments. This work demonstrates the mutual utility of molecular line and dust observations for constraining RSG winds, while highlighting the need for future spatially resolved, multi-tracer observations of RSGC targets to establish the physical structure of their circumstellar environments and improve mass-loss determinations.
Read the full abstract

All authors Mark A. Siebert, Elvire De Beck, Guillermo Quintana-Lacaci, Theo Khouri, Maryam Saberi, Matthias Maercker, Wouter H. T. Vlemmings

Astrophysics of Galaxies

SQuIGG$\vec{L}$E: Ubiquitous Cool Gas Outflows with Large Mass-Loading Factors in $z\sim0.7$ Post-starburst Galaxies

Yuanze Luo, Justin S. Spilker, David J. Setton et al. (+13 more)

While recent James Webb Space Telescope studies have highlighted cool gas outflows as an important mechanism for rapid quenching at $z\gtrsim2$, such space-based spectroscopic samples remain limited in size. In this work, we search for and characterize cool gas outflows traced by Fe II $\lambda\lambda$2586,2600 and Mg II $\lambda\lambda$2796,2803 absorption in post-starburst galaxies (PSBs) at $0.5<z<0.9$, which are accessible to ground-based spectroscopy. Utilizing the SQuIGG$\vec{L}$E survey containing over 1300 PSBs, we stack spectra in bins of stellar mass, (specific) star formation rate, burst mass, burst mass fraction, and time since quenching. We observe blueshifted line centroids indicative of outflows in all stacks except the one containing galaxies that quenched more than 260 Myr ago. Outflow velocities decline with increasing time since quenching, while showing little correlation with other galaxy properties. The inferred outflows have large mass loading factors of 1 – 120, maximum velocities above the interstellar medium escape velocities of their host galaxies, and energy and momentum fluxes exceeding those expected from the current star formation. Our results suggest that cool gas outflows are ubiquitous in intermediate-redshift PSBs and are likely relic outflows launched by previous starburst or AGN activity. These outflows have the potential to quench star formation by transporting gas into the galactic halos, consistent with outflows playing an important role in rapid quenching from intermediate to high redshift.
Read the full abstract

All authors Yuanze Luo, Justin S. Spilker, David J. Setton, Timothy Heckman, Rachel Bezanson, Vincenzo R. D'Onofrio, Alex Geiger, Andy D. Goulding, Jenny E. Greene, Kate Rowlands, Katherine A. Suess, Elizabeth Taylor, Margaret E. Verrico, Andrew Weldon, Vivienne Wild, Pengpei Zhu

Astrophysics of Galaxies

SQuIGG$\vec{L}$E: Spatially resolved NIRSpec Pa$\alpha$ reveals that the most CO-luminous, $z\sim0.7$ post-starburst galaxies exhibit falling—but still active—star formation behind optically thick dust

David J. Setton, Jenny E. Greene, Rachel Bezanson et al. (+13 more)

One of the fundamental uncertainties in the study of galaxies at the interface between star formation and quiescence–post-starburst galaxies–is their instantaneous star formation rate. While these galaxies appear quiescent in the rest UV-optical, many of the youngest systems are highly CO luminous, implying dense molecular gas, and potentially star formation. However, their instantaneous star formation rates have proved elusive, as measurements with rest-optical emission lines or UV-to-IR SED fitting yield order-of-magnitude uncertainty. Here, we present JWST/NIRSpec G395M/170LP integral field spectroscopy of the three most CO-luminous massive galaxies in the SQuIGG$\vec{L}$E survey, spatially resolving Pa$\alpha$/Br$\gamma$/Br$\beta$ to map the dust-corrected star formation rate. We find that these galaxies host star formation rates of $27-80$ $M_\odot \ \mathrm{yr^{-1}}$, though $\sim30-40\%$ of the emission may arise from non-star-forming ionization (AGN or shocks), implied by high [FeII]/Pa$\alpha$ in central spaxels. We also find effective $A_{\mathrm{Pa}\alpha}\sim1$ and individual $\sim700$ pc spaxels with $A_{\mathrm{Pa\alpha}}\sim2$, implying significant dust obscuration of nebular regions that contribute little to the rest-optical lines. These galaxies are not consistent with total quiescence; the measured star formation rates place these galaxies on or above the main sequence. However, their star formation rates are significantly lower ($\sim0.5-1$ dex) than the peak star formation rates inferred from spectrophotometric fitting. We propose that the CO luminous post-starburst phase represents the last gasp of star formation in galaxies on the rapid quenching pathway, and that dust-obscured star formation, outflows, and (speculatively) an uncertain CO-to-H2 conversion reconcile their gas exhaustion with observed timescales of fading.
Read the full abstract

All authors David J. Setton, Jenny E. Greene, Rachel Bezanson, Katherine A. Suess, Justin S. Spilker, Vincenzo R. D'Onofrio, Elia Cenci, Robert Feldmann, Alex J. Geiger, Andy D. Goulding, Mariska Kriek, Anika Kumar, Yuanze Luo, Desika Narayanan, Margaret E. Verrico, Pengpei Zhu

Astrophysics of Galaxies

A solution to the paradox of youth in the Galactic centre

Rodrigo P. Silva, Alexandre C. M. Correia, Tjarda C. N. Boekholt et al. (+1 more)

The supermassive black hole at the Galactic centre, Sgr A*, is surrounded by an S cluster of young stars. These stars are predominantly B-type stars, but their origin remains uncertain. Unlike massive stars in the Galactic field, which exhibit a binary fraction of about $70\%$, those in the S cluster show a significantly lower fraction. It is key to understand this discrepancy for constraining their formation. We show that the binary deficit arises naturally from dynamical interactions between stellar binaries and Sgr A* in an in situ formation scenario. Using K-amplitude data, we derived an observational binary fraction of $f_{\mathrm{obs}} = 0.43 \pm 0.09$ for the S-cluster stars. Our dynamical modelling predicts that interactions with Sgr A* cause $18\%$ of the binaries to merge, $20\%$ to be disrupted, and $62\%$ to survive, yielding a theoretical binary fraction of $f_{\mathrm{theo}} = 0.38 \pm 0.10$. The predicted binary fraction with distance from Sgr A* is also consistent with independent observational constraints. These results show that the decline in binarity towards the Galactic centre is driven by stronger tidal forces, and they support an in situ origin of the S cluster in the same event that produced the Fermi bubbles.
Read the full abstract

All authors Rodrigo P. Silva, Alexandre C. M. Correia, Tjarda C. N. Boekholt, Paulo J. V. Garcia

Astrophysics of Galaxies

H2 emission in the Orion Bar, NGC7023 and the Horsehead Nebula observed with the James Webb Space Telescope

M. Zannese, A. Sidhu, A. Guerras et al. (+25 more)

Molecular hydrogen (H2), the most abundant molecule in the interstellar medium, is a handy tool to study Photodissociation Regions. The JWST, with its high spatial resolution, sensitivity, and wavelength coverage, provides unique access to the detection and spatial morphology of the H2 rotational and rovibrational lines. Our goal is to analyze H2 line emission detected with JWST in several PDRs (the Orion Bar, NGC7023, and the Horsehead Nebula) to constrain the physical structure of dissociation front, and compare the impact of the ultraviolet field and the gas density across different regions. The analysis of H2 spatial morphology reveals similar filamentary structures across all regions. Spatial shifts between H2 lines (0.5") are observed and linked to differences in excitation mechanisms (thermalized vs FUV-pumped lines) and the temperature gradient. Despite differences in incident irradiation conditions, analysis of H2 rotational excitation yields high gas temperatures that are similar across the three PDRs. This is expected for a certain regime of excited PDRs (such as Orion and NGC7023), where the G0 at the DFs and the density are similar. However, it is surprising for less excited PDRs like the Horsehead Nebula. OPRs in the rotational and rovibrational levels differ across the three PDRs. We also used H2 rovibrational lines and the 0-0 S(3) line to estimate the visual extinction across the field of view, yielding markedly different results that constrain both the geometry and the grain composition. Due to the complex 3D geometry, H2 emission is observed throughout the FOV and is dominated by the thin UV illuminated layer, making H2 an unreliable tracer of gas temperature in deeper and coolers molecular layers of the PDR. Therefore, H2 emission is not sufficient to trace the possible temperature and density gradient across PDRs and must therefore be associated with other tracers.
Read the full abstract

All authors M. Zannese, A. Sidhu, A. Guerras, M. Pound, M. Wolfire, A. G. G. M. Tielens, E. Peeters, E. Habart, A. Abergel, M. Baes, O. Berné, C. Boersma, E. Bron, J. Cami, R. Chown, E. Dartois, P. Dell'Ova, J. R. Goicoechea, K. D. Gordon, P. Guillard, O. Kannavou, K. Misselt, N. Monnier, A. Noriega-Crespo, T. Onaka, D. Van de Putte, L. Verstraete, A. N. Witt

Astrophysics of Galaxies · Cross-listed from astro-ph.IM

MATISSE-py: a high-level Python interface for efficient, automated VLTI/MATISSE data reduction

A. Soulain, A. Matter, P. Berio et al. (+4 more)

The Multi AperTure mid-Infrared SpectroScopic Experiment (MATISSE) at the Very Large Telescope Interferometer (VLTI) delivers rich mid-infrared interferometric datasets that are reduced through a robust, multi-stage ESO pipeline. In its native form, however, the reduction relies on command-line calls to esorex, hand-edited set-of-files (SOF) and configuration files, and manual iterations that are difficult to automate, reproduce, or integrate into modern Python workflows. We present MATISSE-py, a modular Python interface that wraps the official ESO esorex recipes behind a single, user-friendly matisse command. It automates discovery, reduction, calibration, and inspection of the data, and ships as a tested, open-source package built on industry-standard practices. Beyond convenience, MATISSE-py introduces science-grade improvements developed over seven years of MATISSE operations: visibility- and photometry-factor (V-factor and P-factor) corrections derived from the GRAVITY fringe tracker to mitigate residual visibility losses, per-baseline data filtering, beam-commuting-device (BCD) "magic-number" corrections, and an absolute spectrophotometric flux calibration using state-of-the-art reference spectra. On faint targets observed under degraded conditions, the V-factor correction recovers up to a few percent of lost visibility and reduces the statistical uncertainties by nearly 20%, while yielding calibrator diameters that are consistent across BCD modes. MATISSE-py thus consolidates the consortium's expertise into a maintainable package and shortens the reduction-to-science loop for the community.
Read the full abstract

All authors A. Soulain, A. Matter, P. Berio, F. Millour, B. Lopez, R. Petrov, S. Lagarde

Astrophysics of Galaxies

ATLASGAL: The HCN-IR Star Formation Relation for the Milky Way

I. I. Grozdanova, J. S. Urquhart, W.-J. Kim et al. (+8 more)

We examine the relation between star formation and dense gas, traced by HCN(1-0), using a sample of 343 Galactic clumps spanning the full range of evolutionary stages representative of high-mass and cluster formation, including quiescent, protostellar, young stellar object (YSO), and HII regions. Earlier Galactic studies, based primarily on luminous HII regions, reported a linear correlation between infrared (IR) and HCN luminosities, consistent with extragalactic surveys, and interpreted it as a universal star formation law. Our larger evolutionary sample yields a significantly steeper slope of $1.80\pm0.08$, inconsistent with extragalactic trends. However, we find that each of the star-forming evolutionary stages individually has a shallower slope ($\sim$1.2) than that of the full sample, with quiescent clumps showing no correlation. We estimate the Milky Way's total IR and HCN luminosities from dense clumps by integrating the bolometric luminosities and clump masses of Hi-GAL sources. Both fall significantly below extragalactic values, demonstrating that clumps alone cannot account for the IR-HCN relation. Only $\sim$5-25 per cent of Galactic HCN luminosity arises from dense clumps, implying that most extragalactic HCN traces gas that is not involved in star formation. Additionally, dense clumps contribute only $\sim$2-3 per cent of the Milky Way's IR luminosity, which is dominated instead by extended HII regions and PDRs tracing longer star formation timescales. As a result, the observed linear relation in nearby galaxies reflects a nearly constant star formation efficiency averaged over large areas and long timescales, rather than a direct link between SFR and dense gas mass.
Read the full abstract

All authors I. I. Grozdanova, J. S. Urquhart, W.-J. Kim, F. Wyrowski, T. Csengeri, A. Karska, A. Giannetti, D. Colombo, D. Eden, M. A. Thompson, T. J. T. Moore

Astrophysics of Galaxies · Cross-listed from astro-ph.SR

The NEMESIS general YSO catalogue - I. Supervised classification with deep learning methods

G. Marton, M. Madarász, J. Roquette et al. (+4 more)

In modern large-scale surveys, young stellar objects (YSOs) are mostly identified by the infrared excess in their spectral energy distributions (SEDs). To this end, YSO identification and classification were mostly based on certain colours, resulting in wavelength-specific methods. Using all available data allows us to construct a uniformly classified YSO catalogue by applying the same identification method to heterogeneous samples, reducing systematic differences and enabling more consistent studies of YSO populations and star formation. Our goal is to develop a method that takes advantage of the heterogeneous data available in the VizieR database and to provide a tool that can be used to identify YSOs with high accuracy. We also aim to create the largest homogeneous catalogue of YSOs. We use the CDS VizieR and NASA/IPAC IRSA to collect data for a large number of objects of various types. The data collected included SEDs, light curves, and direct imaging and were used to build different image representations. These were used to teach deep learning algorithms to differentiate between YSOs and all other types of sources. Architectures from the PyTorch library and custom-built convolutional neural networks were applied to create an ensemble of binary classifiers specialised at identifying YSOs. The resulting method is able to automatically identify YSO candidates with an accuracy higher than 90% while contamination is identified with an accuracy higher than 99%. We applied our classifier to numerous YSO catalogues to confirm the youth of the stars and to create the largest catalogue of homogeneously identified potential YSOs ever – the NEMESIS General YSO catalogue contains 274\,408 unique, high reliability YSOs. Their positions on the colour-magnitude diagrams, and their distribution relative to the local Galactic structures, were also used to test their young nature.
Read the full abstract

All authors G. Marton, M. Madarász, J. Roquette, M. Audard, I. Gezer, D. Hernandez, O. Dionatos

Astrophysics of Galaxies · Cross-listed from astro-ph.CO

Probing the cosmic web with fast radio bursts: II. Scintillation

Sharon Lapiner, Nir Mandelker, Paz Beniamini et al. (+1 more)

We consider the formation of multiphase gas in cosmic web objects (CWOs) through cooling and fragmentation within the shock-heated medium of cosmic sheets and filaments, and the circumgalactic medium (CGM) of haloes. This leads to dense, cool ($\sim10^{4}\,\mathrm{K}$), small-scale cloudlets in pressure equilibrium with their surroundings. Such ionized overdensities can affect the propagation of radio waves emitted by fast radio bursts (FRBs), allowing us to probe the small-scale structure in CWOs by examining their impact on the scintillation pattern of the observed FRB flux. While we find that the probability of encountering a high-temperature filament or sheet with cold cloudlets is rather small and usually confined to high redshifts, the expected high rates of FRBs may still permit detection through scintillation along rare sightlines. We suggest scintillation from the Milky Way (MW) interstellar medium as a promising probe: CWO plasma screens can suppress it, placing constraints on their cold-gas properties. Filaments and sheets can suppress MW scintillation from sources at $z_\mathrm{S}\gtrsim2$ and $3$, respectively, while cold and turbulent cloudlets in the CGM can be probed by sources at redshifts as low as $z_\mathrm{S}\sim0.5$, constraining remarkably low volume-filling fractions, $f_\mathrm{v}$ (e.g. $f_\mathrm{v}\gtrsim10^{-5}$ for $z_\mathrm{S}\gtrsim2$). To provide testable predictions, we estimate the fraction of FRBs expected to encounter CWOs that may suppress MW scintillation below a given frequency, and express this as a function of the average extragalactic dispersion measure. Future FRB samples could map these constraints onto bounds on the existence and properties of cloudlets in CWOs, such as their density, size, $f_\mathrm{v}$, and turbulence.
Read the full abstract

All authors Sharon Lapiner, Nir Mandelker, Paz Beniamini, S. Peng Oh

Astrophysics of Galaxies

Simulating tidal disruption events in nuclear star clusters

Philip Cho, Kai Wu, Francesco Flammini Dotti et al. (+5 more)

Context. Nuclear star clusters (NSCs) and supermassive black holes (SMBHs) often coexist at the centers of galaxies, engaging in complex dynamical interactions that influence SMBH growth. Stars that approach the SMBH too closely are tidally disrupted, and a fraction of their debris is accreted onto the black hole. Such events may contribute to SMBH growth in gas-deficient galaxies. Aims. Our work aims to improve the theoretical framework for understanding the mass accretion of stellar debris following tidal disruption events (TDEs) through numerical simulations. We perform direct N-body simulations of an NSC with a central SMBH embedded in a fully self-consistent dynamical model to test a new TDE accretion prescription in a set of pilot simulations. Methods. The previous TDE prescription used a fixed accretion radius and assumed that the entire stellar mass was accreted after disruption. In the new partial-mass accretion model, the mass added to the SMBH depends on the orbital eccentricity and penetration factor of the disrupted star. Results. We find that most TDEs involving main-sequence stars are marginally eccentric or marginally hyperbolic and contribute approximately half of the stellar mass to SMBH growth, consistent with recent hydrodynamical simulations. In all simulated models, the TDE-driven mass accretion rate exhibits an early peak followed by a rapid decline. Models with higher initial SMBH masses exhibit a faster decline in the accretion rate, consistent with more rapid loss-cone depletion and inefficient replenishment
Read the full abstract

All authors Philip Cho, Kai Wu, Francesco Flammini Dotti, Taras Panamarev, Shuo Li, Shiyan Zhong, Klaus Reuter, Rainer Spurzem

Astrophysics of Galaxies

AKARI near-infrared spectroscopy of circumstellar hydrocarbon dust associated with young stellar objects

Yuki Kuroda, Hidehiro Kaneda, Natsuko Izumi et al. (+2 more)

We investigate the processing of the circumstellar polycyclic aromatic hydrocarbons (PAHs) associated with young stellar objects (YSOs) through their stellar activities. We analyze the AKARI near-infrared (2.6$-$4.4 $\mu$m) long-slit spectral data of 10 YSOs, focusing on the aromatic feature at a wavelength of 3.3 $\mu$m and the aliphatic features at 3.4$-$3.6 $\mu$m. The spectral fitting results show large variations from target to target in the flux ratio of the aliphatic to aromatic features, the shape of the aliphatic feature profile, and the central wavelength of the aromatic feature. In particular, HD 97048 and Elias 1 show strong aliphatic features at wavelengths longer than 3.5 $\mu$m, which is consistent with the hydrogenated nanodiamond features reported in previous studies. We find that the properties of the hydrocarbon dust vary under the influence of the YSO activity, where the degree of dust processing is likely to be related to the age of the YSO and the amount of the circumstellar dust. In addition, correlation is observed between the variations of the H$_2$O and CO$_2$ ice features and the aliphatic feature profiles, suggesting connection between the formation of CO$_2$ ice and the processing of aliphatic hydrocarbons. Finally, we find a significant correlation between the variations in the central wavelength of the aromatic feature and the shape of the aliphatic feature profile. These findings may be consistent with a tentative scenario in which circumstellar PAHs are converted to nanodiamonds through irradiation by high-energy particles produced by YSO activity.
Read the full abstract

All authors Yuki Kuroda, Hidehiro Kaneda, Natsuko Izumi, Takuma Kokusho, Shinki Oyabu

Astrophysics of Galaxies · Cross-listed from astro-ph.SR

Near-infrared spectra of chemically peculiar stars and applications to kilonova spectra

Nanae Domoto, Masaomi Tanaka, Wako Aoki et al. (+11 more)

Kilonova spectra provide information on rapid neutron-capture nucleosynthesis in neutron star mergers. However, it remains challenging to identify individual elements in kilonova spectra, primarily due to incomplete atomic data for heavy elements at near-infrared wavelengths. Recent work demonstrated that spectra of chemically peculiar stars offer excellent laboratory for studying kilonova spectra. In this paper, to expand our understanding of strong transitions of heavy elements at near-infrared wavelengths, we present high-resolution near-infrared spectra of 14 chemically peculiar stars covering a range of effective temperatures, surface gravities, and abundance patterns, obtained with Subaru/IRD. The Sr II, Ce III, and Gd III lines, previously suggested to be among the strongest transitions, are detected in the spectra of most of our targets, confirming their intrinsic importance. In addition, Eu II and Nd III lines are detected in several stars. By comparing observed equivalent widths and abundance ratios, we show that under a highly heavy-element-enriched abundance pattern, Eu II and Nd III lines may contribute to kilonova spectral features comparably to Sr II. Importantly, we find no unidentified lines systematically stronger than these transitions despite the larger stellar sample. These results further support the primary importance of the Sr II and Ce III transitions and provide new insights into the potential contribution of Eu II and Nd III.
Read the full abstract

All authors Nanae Domoto, Masaomi Tanaka, Wako Aoki, Salma Rahmouni, Tomoyuki Kudo, Hiroki Harakawa, Teruyuki Hirano, Takayuki Kotani, Takashi Kurokawa, Masayuki Kuzuhara, Jun Nishikawa, Takuma Serizawa, Motohide Tamura, Akitoshi Ueda

Astrophysics of Galaxies

KBSS-InCLOSE II: First Detailed Insights on the Inner CGM of Low-Mass $z\sim2.3$ Galaxies

Evan Haze Nunez-Cravin, Charles C. Steidel, Gwen C. Rudie et al. (+7 more)

We present results from an extension to the Keck Baryonic Structure Survey (KBSS) that focuses on the Inner Circumgalactic Medium (CGM) of QSO Line Of Sight Emitting galaxies at z$\sim$2.3 (InCLOSE). We analyze two low-mass galaxies $\log{(\rm{M_*} / \rm{M_\odot})} \leq 9$ that are within small a projected distance of a QSO $D_{\rm tran} \leq 50~{\rm kpc}$ ($D_{\rm tran} /R_{\rm vir} \leq 0.75$). One galaxy is detected as a bright Lyman- Emitter with Keck/KCWI (confirmed with follow-up Keck/MOSFIRE spectra), and the other as a serendipitous line emitter with Keck/MOSFIRE. Both galaxies have nebular and morphological properties consistent with those of typical low-mass z$\sim$2.3 star-forming galaxies. Analysis of their CGM absorption as seen with Keck/HIRES spectra of the background QSOs shows no detections of low-ionization metal absorption (low-ions; e.g., Si II), ubiquitous detections of intermediate- (e.g., C IV) and high-ions (O VI), kinematically complex absorption ($\geq$7 components per galaxy halo) spread over $|\Delta v|\pm 150~{\rm km~s^{-1}}$, and no unambiguously unbound gas is detected in either galaxy halo. We analyze the thermal properties of a subset of CGM components, finding that the majority (6/10) have temperatures consistent with heating from the metagalactic UV background ($\log{(T/\rm{K})_{\mathrm{med}}}=4.0$) while the remainder possess short-lived, intermediate temperature gas that would require additional heating or rapid replenishment ($4.6 \leq \log{(T/\rm{K})} \leq 5.1$), the internal energy of these absorbers are dominated by thermal broadening, their internal (turbulent) velocities are all subsonic, while their motions through the halo are likely supersonic. These results hint that the z2.3 CGM changes with stellar mass in terms of kinematic complexity and unbound gas fraction, while thermal properties remain similar.
Read the full abstract

All authors Evan Haze Nunez-Cravin, Charles C. Steidel, Gwen C. Rudie, Evan N. Kirby, Charis M. Hall, Nikolaus Z. Prusinski, Zhuyun Zhuang, Yuanze Ding, Alice E. Shapley, Ryan F. Trainor

Astrophysics of Galaxies · Cross-listed from astro-ph.EP

On the Compositions of Interstellar Objects

Matthew J. Hopkins, Michele T. Bannister, Bertram Bitsch et al. (+2 more)

As physical samples of distant planetary systems, the compositions of interstellar objects (ISOs) should correlate with the properties of their diverse parent stars. We combine a chemical partition model with a sample of stellar elemental abundances from APOGEE DR17 to predict the abundances of commonly-observed cometary volatiles in ISOs. We find that the compositions of ISOs vary significantly between different stars. In particular, we predict a strong correlation between an ISO's ammonia abundance and its parent star's metallicity: high-metallicity stars will create ISOs rich in ammonia. This suggests the production rates of NH$_3$'s photolytic daughter products are an ideal observational tracer for the origins of ISOs. We infer that 2I/Borisov formed around a star of near-solar metallicity ($-0.4\lesssim[\mathrm{Fe}/\mathrm{H}]\lesssim0.3$), and corroborate the velocity- and isotope-based inferences that 3I/ATLAS formed around a lower-metallicity star ($-0.8\lesssim[\mathrm{Fe}/\mathrm{H}]\lesssim0.0$). The production rates of 2I and 3I imply both only contain hypervolatiles such as CO and N$_2$ that are trapped in other less-volatile ices, similar to typical Solar System comets. Despite this, we argue that true hypervolatile-ice-rich ISOs may exist; they would exhibit high CO and N$_2$ production rate ratios, possibly similar to those of C/2016 R2 (PanSTARRS). Our predictions provide context for future ISO discoveries, opening a path to link the properties of their origin systems to observable production rates.
Read the full abstract

All authors Matthew J. Hopkins, Michele T. Bannister, Bertram Bitsch, Chris Lintott, John C. Forbes

Astrophysics of Galaxies · Cross-listed from astro-ph.SR

A Sample of Long-Period Binaries with Dormant Compact-Object Candidates from LAMOST DR13 MRS and Gaia DR3

Junxing Zhou and Wei-Min Gu

Identifying dormant compact objects in non-interacting binaries is crucial for constraining the hidden population of stellar remnants. We present a systematic search for long-period compact-object candidates by combining Gaia DR3 astrometry with multi-epoch LAMOST DR13 medium-resolution spectroscopy. Starting from sources with elevated RUWE values, we required at least five LAMOST spectroscopic epochs and peak-to-peak RV variations exceeding 20 km/s. After RV extraction, orbital fitting, and subsequent screening, we obtained Bayesian Keplerian orbital solutions for 19 long-period single-lined binary candidates, with periods spanning approximately 30-1500 days. Multi-wavelength spectral energy distribution fitting was used to constrain the visible stars and evaluate the expected luminosities of unseen companions under a main-sequence assumption. Two systems are identified as the highest-priority compact-object candidates in our sample, each with a minimum companion mass exceeding 1 solar mass. Their spectra and optical-to-infrared photometry show no detectable secondary-light contribution, although such a contribution would be expected if the unseen companions were normal main-sequence stars. These systems therefore represent the strongest compact-object candidates in our sample, although further observations are required to distinguish massive white dwarfs or neutron stars from faint stellar companions or unresolved hierarchical systems. We also identify five intermediate-priority and 12 lower-priority systems for follow-up spectroscopy, ultraviolet imaging, and future astrometric constraints.
Read the full abstract

Astrophysics of Galaxies

A Cyanopolyyne-rich but COM-poor Massive Protostar: The First Hot Carbon Chain Chemistry Source G28.28-0.36

Kotomi Taniguchi, Masao Saito, Prasanta Gorai et al. (+6 more)

We present molecular emission line data from the massive young stellar object (MYSO) G28.28-0.36 (G28.28) obtained with the Atacama Large Millimeter/submillimeter Array Band 3. Cyanopolyynes (HC$_3$N and HC$_5$N) and three complex organic molecules (COMs; CH$_3$OH, CH$_3$CN, and CH$_3$CHO) are detected from the MYSO G28.28. In addition, strong emission regions of cyanopolyynes are identified between G28.28 and a nearby ultracompact H II region. The HC$_5$N emission is coincident with the dust continuum peak, where an excitation temperature of 100 K is derived from CH$_3$CN. These results suggest that the Hot Carbon Chain Chemistry (HCCC) mechanism produces cyanopolyynes in the hot region around G28.28. We find that G28.28 exhibits a unique chemical feature: cyanopolyynes are abundant, but COMs are deficient, unlike the other MYSOs studied previously. These results imply that G28.28 is a counterpart of the Warm Carbon Chain Chemistry (WCCC) low-mass source L1527. G28.28 is the first HCCC source identified so far.
Read the full abstract

All authors Kotomi Taniguchi, Masao Saito, Prasanta Gorai, Olli Sipilä, Kazuhito Dobashi, Paola Caselli, Tirupati Kumara Sridharan, Tomomi Shimoikura, Jonathan C. Tan