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Physics Astrophysics Astrophysics of Galaxies

astro-ph.GA Watch Astrophysics of Galaxies

Wednesday 7 October

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

On the origin of the short-period Blue Straggler Stars in Collinder 261: a binary evolution approach

M. Echeveste, M. J. Rain, G. Carraro et al. (+3 more)

Building on the recent publication of a fresh catalog of blue straggler stars in Galactic open clusters using Gaia DR3, we conduct a study focusing on the blue straggler stars with short-period photometric variability found in the open cluster Collinder 261: nine eclipsing or ellipsoidal binaries and five SX Phe pulsator candidates. Our investigation delves into the potential of mass transfer in binary systems to account for the presence and properties of these stars. We first measure their photometric periods and classify the variables into eclipsing/ellipsoidal binaries, SX Phe pulsator candidates, and instrumental aliases or blends. Subsequently, we perform a set of simulations based on comprehensive calculations of the structure of both stars within the binary system, as well as their orbital evolution and mass transfer rates. To compare with observations, we solved the atmospheric structure of each stellar component and computed filter-weighted integrated fluxes in the Gaia DR3 passbands, obtaining a combined evolutionary sequence that accounts for the unresolved flux of both stars as seen photometrically. Our investigation includes the study of several parameters, such as the initial mass of both stars, the initial orbital period, and the efficiency of mass transfer. The aim is to identify potential progenitor candidates matching color-magnitude diagram observations at the same age as that determined for Collinder 261. We find that binary evolution serves as a viable mechanism for producing these eclipsing blue stragglers and that the efficiency of mass transfer plays a key role in accurately matching the fainter objects.
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All authors M. Echeveste, M. J. Rain, G. Carraro, O. G. Benvenuto, J. A. Panei, M. A. De Vito

Astrophysics of Galaxies

Star Formation in the Low Surface Brightness Galaxies: a Comparison with the Outer Regions of Normal Galaxies

Anatoly Zasov, Natalia Zaitseva and Anna Saburova

Low surface brightness galaxies (LSB-galaxies) and the outer regions of disks of "normal" surface brightness galaxies (HSB-galaxies) are compared in terms of the radial distributions of star formation rates and efficiencies, as well as the Toomre stability parameter $Q_T$, using data from several samples of galaxies with high $HI$ content. It is shown that the dependences of the star formation rate $SFR$ on the $HI$ surface density and the star formation efficiency $SFE$ on the disk optical brightness $\mu_g$ for LSB- and HSB-galaxies have a similar character, suggesting similarity in the conditions that determine the star formation rate in low gas density regions. The considered dependences persist out to distances corresponding to brightnesses of 26-27 mag/arcsec$^2$, where the expected volume density of the equilibrium gas layer should be very low. It is suggested that the disk density at large distances from the center may be significantly underestimated.
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Astrophysics of Galaxies

Registering Gaia positions on VLBI images: constraining opacity-driven core shift in B 1038+528 / B 1038+529

M. H. Xu and Y. Y. Kovalev

Because of the complex and time-variable radio structure of active galactic nuclei (AGNs), absolute astrometric positions cannot generally be registered unambiguously with specific features in VLBI images. We aim to register Gaia optical centroids on VLBI images with about 0.1 mas accuracy and to locate the optical emission relative to the radio core in the quasar pair B 1038+528 and B 1038+529, in which the opacity-driven core shift was first discovered. We combine the relative position of the pair from phase-referenced VLBI at four epochs between 1981 and 1995, their Gaia optical positions, and the nearly orthogonal radio-jet directions. Assuming that each Gaia–core displacement lies along the local jet axis, we register the Gaia centroids relative to the radio cores with about 0.1 mas accuracy without using absolute VLBI positions. The Gaia centroids lie upstream of the 8.4-GHz radio cores, by 293 {\pm} 93 {\mu}as in B 1038+529 and 169 {\pm} 96 {\mu}as in B 1038+528. The latter agrees with the 260 {\mu}as 8.4-GHz core shift implied by the 2.3–8.4 GHz shift measured for this quasar four decades ago. The absolute astrometric position of B 1038+528 with VLBI lies about 0.6 mas downstream of the core, and its geodetic position time series drifts along the jet by more than 1 mas, showing that the 0.8–1.6 mas Gaia–VLBI offsets of the pair are dominated by source structure rather than by core shift. Gaia positions can be registered on VLBI images with an accuracy set by the astrometry uncertainties. If the Gaia centroids mark the jet base, the measured separations are absolute 8.4-GHz core shifts, corresponding to projected distances of about 1.2 pc and about 2.5 pc from the jet base; a contribution from an optical jet emission would make them lower limits. The method is applicable to AGNs with Gaia detection and phase-referenced VLBI astrometry.
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Astrophysics of Galaxies

SAGE26 Paper I: Modelling the baryon cycle from cosmic dawn to the present day

Michael Bradley, Darren J. Croton, Robert Adriel Mostoghiu Paun et al. (+2 more)

We present SAGE26, a comprehensive update to the Semi-Analytic Galaxy Evolution (SAGE) model. SAGE26 integrates five observationally motivated improvements: (1) distinct circumgalactic medium and hot-halo gas physics, (2) molecular hydrogen for star formation, (3) velocity- and redshift-dependent supernova feedback, (4) bulge radii tracking through time, and (5) feedback-free burst galaxies. Each improvement works to regulate galaxy formation from cosmic dawn to the present. Most significantly, the addition of feedback-free burst galaxies provides a pathway to produce high-redshift massive galaxies at the abundances observed by the James Webb Space Telescope. Furthermore, the new circumgalactic medium framework improves the treatment of baryons by distinguishing between free-fall-limited inflow in low-mass haloes and hydrostatic cooling in massive groups and clusters using a characteristic halo shock mass. SAGE26 reproduces key observational constraints across cosmic time, including the stellar mass function and cosmic star formation rate density, while retaining the computational efficiency and flexibility of its predecessor. The code and data products are open-source and publicly available.
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All authors Michael Bradley, Darren J. Croton, Robert Adriel Mostoghiu Paun, Dhruba Dutta Chowdhury, Jayde Willingham

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

Light curve spectral energy distribution fitting of 13 carbon-rich Mira variables stars in the Small Magellanic Cloud

A. Liberatori, M. Trabucchi, D. Hatzidimitriou et al. (+8 more)

Carbon-rich Mira variables are highly dynamic stars characterized by large-amplitude radial pulsations and intense mass-loss. Standard spectral energy distribution (SED) fitting often relies on time-averaged observations, which flatten intrinsic variability and yield only approximate stellar and circumstellar parameters. To overcome these limitations, we dynamically trace the physical parameters of 13 carbon-rich Miras in the Small Magellanic Cloud (SMC) throughout their pulsation cycles. Combining time-series photometry from $Gaia$, WISE, VMC, 2MASS, and OGLE, we reconstruct simultaneous multi-band light curves. We extract independent SEDs at 14 distinct phases and model them using the ATHENA-C grid. This phase-resolved approach traces cyclic variations in effective temperature ($T_{\rm eff}$), optical depth ($\tau_{0.55}$), and bolometric luminosity. We find peak-to-peak $T_{\rm eff}$ variations ranging from $\sim 100$ K to $>1000$ K. A strong anti-correlation between $\tau_{0.55}$ and bolometric luminosity indicates the dust condensation zone is pushed outward at maximum brightness, rendering the circumstellar environment optically thinner. We also recover the classical Period-Luminosity relation and derive radial expansion velocities and radius variation amplitudes, which are consistent with independent measurements. Phase-resolved fitting reveals the true dynamic ranges of these parameters, which static fits fail to capture. Although limited by grid sampling and gaps where converged hydrostatic models are unavailable, explicitly accounting for time-dependent behavior provides a much more physically realistic picture of the interplay between stellar pulsation and dust formation. This highlights the critical need for time-resolved methodologies when studying large-amplitude variables.
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All authors A. Liberatori, M. Trabucchi, D. Hatzidimitriou, M.A.T. Groenewegen, A. Bressan, G. Pastorelli, L. Girardi, K. Shepherd, B. Aringer, A. Udalski, A. Nunnari

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

ASTRAL: A Framework for Optimal Placement and Emulation of Stellar Evolution Models

Trevor Gravely, Marko Ristić and Brandon Barker

Generating dense grids of detailed stellar evolution simulations is computationally prohibitive, as resolving progressively complex nucleosynthesis chains and dynamical timescales incurs a rapidly increasing computational cost that scales with dimensionality and resolution. Existing simulation grids are sparse, heterogeneous, and often cover disparate regions of parameter space, limiting (direct) systematic comparison and broader generalization to downstream science analyses. We present ASTRAL (Active Simulation Tuning and Regression for Astrophysical Libraries), a publicly available framework for optimal placement and emulation of stellar evolution models. The ASTRAL framework builds surrogate models that provide a continuous representation of the parameter space which is populated by sparse simulation grids. Furthermore, ASTRAL interpolates across the simulation parameter space (e.g. zero-age-main-sequence mass) to predict stellar properties of stars with associated uncertainty estimates for systems not explicitly simulated. We show that ASTRAL significantly outperforms uniform placement in constructing emulation-ready model libraries that capture both global and local variability in the output features. We showcase the performance of our framework in the context of a simple, one-dimensional MESA model. Finally, we examine how our methodology can inform downstream applications by analyzing our emulator's predictive confidence when applied to supernova simulations. We emphasize that, while developed for stellar evolution, the ASTRAL framework is directly extensible to other simulation-driven domains where model evaluations are expensive and parameter spaces are high-dimensional.
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Astrophysics of Galaxies

Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) V. Tracing cavity walls and shocked knots with nonthermally desorbed CH$_3$OH in BHR71-IRS1

H.-S. Yun, J.-E. Lee, J. K. Jørgensen et al. (+16 more)

Complex organic molecules are detected in both cold molecular clouds and the warm inner regions of protostars. Whether they are eventually inherited by protostars and planets or whether their chemistry is reset by in situ reactions remains unclear. Understanding the desorption mechanisms of these molecules is essential for tracing their chemical evolution. As part of the ALMA Large Program Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS), we investigate the CH$_3$OH emission that extends beyond the hot corino of BHR71-IRS1. We identified extended CH$_3$OH emission around BHR71-IRS1. We assessed characteristic emission structures by applying a principal component analysis. The physical properties of their line-emitting gas were derived under the local thermodynamic equilibrium (LTE) assumption through both rotational diagram and spectral modeling analyses. In total, 26 extended CH$_3$OH lines have been detected. These emission lines are distributed across (1) X-shaped cavity walls, (2) northern and southern shocked knots, and (3) eastern and southeastern components. The cavity walls exhibit excitation temperatures of $\sim$ 25~K and column densities of $\sim$ 10$^{14}$~cm$^{-2}$, while the knots show relatively higher excitation temperatures (70$-$120~K) and column densities ($10^{14}-10^{16}$~cm$^{-2}$). The physical properties of eastern and southeastern components are not well constrained under LTE conditions. Plausible desorption mechanisms are evaluated by comparing the physical parameters with model predictions. The low excitation temperatures and narrow line widths in the cavity walls favor a reactive desorption scenario driven by far-ultraviolet irradiation from IRS1. In contrast, the knots with higher excitation temperatures and column densities support the dust sputtering scenario induced by C-type shocks.
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All authors H.-S. Yun, J.-E. Lee, J. K. Jørgensen, A. Coutens, A. L. Plunkett, M. N. Drozdovskaya, A. Belloche, J.-H. Jeong, P. Nazari, Y.-L. Yang, M. L. R. van 't Hoff, S. Maret, F. Cruz-Sáenz de Miera, D. Harsono, C.-H. Kim, Á. Kóspál, M. Lützen, S. Spezzano, S. Zeng

Tuesday 6 October

Astrophysics of Galaxies

(Monty Python and the) HoliGRALE: A Hybrid GRALE Lens Inversion Methodology Diagnostically Evaluated with Synthetic and Real Data

Derek Perera, Jori Liesenborgs, John H. Miller Jr et al. (+4 more)

We present HoliGRALE (Hybrid, only light included, GRAvitational LEnsing), a hybrid lens modeling extension of the freeform method GRALE. HoliGRALE incorporates physically motivated parametric components within the freeform genetic algorithm GRALE. Using three synthetic clusters from IllustrisTNG, each of varying complexity, we evaluate its performance according to its accuracy in reconstructing the density distribution, image positions, magnifications, and time delays. We find that HoliGRALE generally outperforms GRALE on all fronts, and shows greater accuracy in regions containing a high image number density. We estimate the error budget in projected density to be $<5\%$ for simple, few component clusters, and $\sim5-10\%$ for complex, multi-component clusters in the regions constrained by observed images. We then use HoliGRALE to model three lenses: RX J2129.7$+$0005, MACS J0138.0$-$2155, and Abell S1063. In each case, HoliGRALE is able to accurately reconstruct observed magnifications and time delays. In its predictions, HoliGRALE is found to be more precise than GRALE. We particularly highlight the predicted time delay for the next arriving image of SN Requiem to be $4346.61^{+490.27}_{-818.36}$ days ($\approx$ April 2026 – October 2029), consistent with previous work, albeit with less precision. In Abell S1063, we report the reconstruction of a main dark matter halo core radius of $89.9\pm33.2$ kpc, in excellent agreement with past work and useful in testing theories of dark matter. Our results emphasize the expected error budget of HoliGRALE, which should be mentioned and scrutinized in future applications of HoliGRALE for other lens systems.
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All authors Derek Perera, Jori Liesenborgs, John H. Miller Jr, Ashley Francis, Liliya L. R. Williams, Birendra Dhanasingham, Jose M. Diego

Astrophysics of Galaxies

Euclid Quick Data Release (Q1). Exploring the complexity of quenching processes across time, environment, and mass through recently quenched galaxies

Euclid Collaboration: Z. Mao, L. Pozzetti, A. Enia et al. (+307 more)

Recently quenched galaxies (RQGs) provide insights into galaxy quenching. We present a photometric and spectroscopic analysis of RQGs using the first Euclid Quick Data Release (Q1). Using rest-frame UVJ colours, we classify star-forming (SFGs), quiescent (QGs), and recently quenched galaxies at 0.2<z<3.0, separating RQGs into fast- and slow-quenching types (fRQGs and sRQGs) following model evolutionary tracks. The relative fractions of RQGs and their quenching efficiencies both decrease with cosmic time. At early epochs, fast quenching is more efficient in massive galaxies, whereas it becomes efficient only at low masses at later epochs. Slow quenching becomes more efficient at z<1.5, progressing from high to intermediate masses with cosmic time. Most RQGs at z<0.5 reside in low-density environments, while they also exist in high-density environments at z>0.5, suggesting earlier quenching in dense regions. RQGs show intermediate properties between SFGs and QGs in stellar mass, star-formation rate, specific star-formation rate, Sersic index, and radius. Most RQGs exhibit regular morphologies, excluding merger as a primary mechanism. We find that fRQGs retain disc-like morphologies, whereas sRQGs are more concentrated, suggesting different stages of morphological transformation. Our analysis suggests that multiple mechanisms drive quenching. Stacked spectra of galaxies with spectroscopic redshifts confirm old, passive populations in QGs, while sRQG spectrum shows weak Ha emission, indicating residual star-formation activity or AGN contribution. The recently-quenched nature of RQGs is confirmed by strong Balmer absorption lines in stack DESI spectra. The stacked Euclid QG spectrum agrees with previous templates and stellar population models older than 5Gyr at z<1. These results demonstrate Euclid's potential for studying galaxy quenching, to be further enhanced by future releases.[Abrg.]
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All authors Euclid Collaboration: Z. Mao, L. Pozzetti, A. Enia, S. Quai, W. G. Hartley, M. Bolzonella, F. Gentile, G. De Lucia, M. Moresco, N. Borghi, C. Saulder, C. Nipoti, M. Talia, P. Corcho-Caballero, L. Gabarra, Abdurro'uf, L. Wang, L. Bisigello, E. Daddi, M. Siudek, C. D'Eugenio, G. Zamorani, F. Calura, H. Fu, R. Ragusa, F. Shankar, M. Hirschmann, O. Cucciati, T. Kodama, S. Belli, L. Spinoglio, J. R. Weaver, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, F. J. Castander, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, A. Da Silva, H. Degaudenzi, C. Dolding, H. Dole, F. Dubath, X. Dupac, M. Farina, R. Farinelli, S. Ferriol, P. Fosalba, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. Gwyn, S. V. H. Haugan, S. Hemmati, J. Hoar, W. Holmes, A. Hornstrup, M. Huertas-Company, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, V. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, M. Magliocchetti, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, N. Mauri, S. Maurogordato, E. Medinaceli, S. Mei, M. Meneghetti, E. Merlin, G. Meylan, P. Monaco, A. Mora, C. Moretti, L. Moscardini, R. Nakajima, C. Neissner, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, A. Pezzotta, S. Pires, G. Polenta, M. Poncet, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, I. Risso, E. Romelli, M. Roncarelli, H. J. A. Rottgering, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, M. Scodeggio, A. Secroun, G. Seidel, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, L. Stanco, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei, F. M. Zerbi, I. A. Zinchenko, E. Zucca, V. Allevato, M. Ballardini, E. Bozzo, C. Burigana, A. Cappi, T. Castro, J. A. Escartin Vigo, R. Maoli, J. Martín-Fleitas, R. B. Metcalf, A. A. Nucita, M. Pöntinen, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, L. Bazzanini, D. Bertacca, M. Bethermin, F. Beutler, L. Blot, H. Böhringer, M. Bonici, S. Borgani, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, F. Cogato, T. E. Collett, T. Contini, A. R. Cooray, S. Davini, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, P.-A. Duc, V. Duret, M. Y. Elkhashab, Y. Fang, A. Finoguenov, F. Fontanot, A. Franco, K. Ganga, T. Gasparetto, R. Gavazzi, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, C. Hernández-Monteagudo, H. Hildebrandt, J. Hjorth, L. K. Hunt, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, S. J. Liu, X. Lopez Lopez, A. Loureiro, G. Maggio, E. A. Magnier, C. Mancini, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Miluzio, G. Morgante, K. Naidoo, A. Navarro-Alsina, S. Nesseris, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, G. W. Pratt, M. Radovich, G. Rodighiero, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, C. Scarlata, A. Schneider, M. Schultheis, D. Sciotti, E. Sellentin, L. C. Smith, J. G. Sorce, K. Tanidis, F. Tarsitano, G. Testera, R. Teyssier, A. Troja, A. Venhola, D. Vergani, G. Verza, S. Vinciguerra, N. A. Walton, A. H. Wright

Astrophysics of Galaxies · Cross-listed from physics.comp-ph

Convergence of Roberts flow dynamos in Eulerian and Lagrangian codes

Nikyta Shchutskyi, Axel Brandenburg and Matthieu Schaller

Standard benchmark tests for numerical magnetohydrodynamics codes focus on one- and two-dimensional problems that ignore the possibility of dynamos, i.e., an exponential instability converting kinetic energy into magnetic energy. They also tend to ignore magnetic helicity conservation that can have dramatic effects in periodic domains. The existence of magnetic diffusion is crucial for dynamos, as was exemplified by the impossibility of finding dynamo solutions when using Euler potentials, which is a perfectly valid approach in the absence of magnetic diffusion. The Roberts flows~I, II, III, and IV are two-dimensional flows that support three-dimensional dynamos, all of which are also large-scale dynamos in the sense that their planar averages are of significant strengths, even though flow~II is pointwise non-helical. Here we demonstrate the numerical convergence properties of solutions obtained using discretisation schemes of second, sixth, and tenth order in the mesh width in the Pencil Code, compare the results with the SPH-based SWIFT code, and present a list of averaged quantities that facilitate their use in characterising the solutions as benchmarks. In addition, we present a procedure to obtain two-dimensional time-independent magnetic field visualisation for all Roberts flows, and perform per-pixel comparison between the Pencil and SWIFT codes. The rich combination of features makes Roberts flows an excellent dynamo benchmark for the direct numerical simulations of magnetohydrodynamics equations.
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Astrophysics of Galaxies

CHemical Evolution in MassIve star-forming COres (CHEMICO). II. Molecular ions, electron fraction, and cosmic-ray ionisation rate

F. Fontani, E. Roueff, V.M. Rivilla et al. (+5 more)

Molecular ions are crucial in initiating and regulating the formation of molecules in the interstellar medium, and are expected to be sensitive tracers of evolution in star-forming regions. Within the framework of the project `CHemical Evolution of MassIve star-forming COres' (CHEMICO), we investigate the temporal evolution of molecular ions towards three high-mass star-forming cores that represent three sequential evolutionary stages. CHEMICO is based on an unbiased spectral line survey of the bandwidth at 3, 2, and 1.2~mm carried out with the 30m telescope of the Insitut de Radioastronomie millimétrique. We detect 19 molecular ions, including isotopologues. From a local thermodynamic equilibrium analysis, we derive the following main results: (i) Overall, the physical parameters of sulphur-bearing ions are the most sensitive to evolution, whereas those of nitrogen-bearing ions are the least; (ii) The molecular abundances that exhibit the most pronounced temporal variations are those of SO+, DCO+, and N2D+; (iii) A simple analytic approach tailored for warm gas conditions provides cosmic-ray ionisation rates of H2 several orders of magnitude above the canonical values measured in the interstellar medium and with a marked increase with evolution; (iv) The abundance ratio of protonated-to-neutral species increases with the proton affinity of the neutral regardless of the evolutionary stage of the source, indicating that proton-transfer appears to proceed similarly in both cold and warm interstellar environments. Molecular ions exhibit distinct evolutionary trends in high-mass star-forming regions, with sulphur-bearing species and the abundances of N2D+, DCO+, and SO+ emerging as particularly sensitive tracers of evolution. Measured electron fractions and cosmic-ray ionisation rates are in line with an internal production of cosmic-rays that becomes increasingly efficient with time.
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All authors F. Fontani, E. Roueff, V.M. Rivilla, Á. López-Gallifa, L. Bizzocchi, L. Colzi, H. Martín-Caballero, P. Caselli

Astrophysics of Galaxies

Early onset of the hot circumgalactic medium around Milky Way galaxies

Víctor Rufo-Pastor, Oscar Agertz, Santi Roca-Fábrega et al. (+6 more)

Hot coronae are key regulators in Milky Way (MW)-type galaxy formation and are thought to emerge once a galaxy's dark matter halo crosses a critical mass threshold, $M_{\mathrm{vir}}\sim10^{12} {\mathrm{M}}_\odot$, so that accretion shocks can heat infalling gas to virial temperatures, $T_{\mathrm{vir}}$. Here we investigate the roles of stellar feedback and accretion shocks in establishing the circumgalactic medium (CGM) around MW-mass galaxies using the VINTERGATAN cosmological simulation suite. We find that stellar feedback drives the early formation of a hot CGM, with $T_{\mathrm{CGM}}\sim T_{\mathrm{vir}}$. By contrast, in feedback-free simulations, accretion shocks alone do not produce a CGM with comparably high average temperatures at early epochs ($z>2$), independent of gas metallicity. We show that CGM virialisation (defined when halo-gas cooling time exceeds the free-fall time) begins with the emergence of a hot corona ($T>10^5$ K) that can appear as early as $z\approx3$ at virial radius, $R_{\mathrm{vir}}$, when feedback is included. This is much earlier than predicted by accretion-shock theory or feedback-free models ($z\lesssim1$). While accretion shocks alone produce an inside-out virialisation pattern, feedback can alter this behaviour, driving a rapid transition ($\lesssim0.5$ Gyr) that is either outside-in or nearly simultaneous throughout the halo. Finally, these early-forming coronae are largely stable from formation through to the present day, but can appear to evolve simply because the definition of $R_{\mathrm{vir}}$ grows with time. This 'CGM pseudo-evolution' is analogous to the pseudo-evolution of dark matter haloes and should be taken into account when interpreting the evolution of hot coronae.
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All authors Víctor Rufo-Pastor, Oscar Agertz, Santi Roca-Fábrega, Martin P. Rey, Joss Bland-Hawthorn, Justin I. Read, Thor Tepper-García, Corentin Cadiou, Anatole Storck

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

Re-calibrated analytic stellar evolution formulae for the main sequence: Extension to massive stars and variations in $[\alpha/\mathrm{Fe}]$

Conor M Byrne, Elizabeth R Stanway and Jan J Eldridge

Analytic formulae are an efficient way to approximate the evolution of a star of a given mass and chemical composition, and are widely used in the literature to compute large grids of evolutionary models for stellar population synthesis. Such formulae rely on calibration to detailed stellar evolution models, and existing versions are based on a sparse, limited grid in comparison to modern simulations. By calibrating against the latest generation of single-star evolution models calculated within the Binary Population and Spectral Synthesis (\bpass) framework, we revise and extend pre-existing equations to include the evolution of massive ($M\gtrsim50\,$\msun) stars and changes in chemical abundances in the form of variations in \afe. We introduce additional terms which allow for a better approximation of the main-sequence lifetimes, and the luminosities and radii at the beginning and end of the main sequence. These revised equations describe the main-sequence age, zero-age and terminal-age radius and luminosity with mean errors of less than 10 per cent or 0.05 dex, for all except the terminal age radius, which shows RMS errors of 20 per cent and 0.1 dex. For \afe\ enriched stellar populations, we advise using a matched-iron value for metallicity in the equations, consistent with the expectation that iron is the dominant opacity source affecting the evolution of main-sequence stars.
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2610.08930 · 6 Oct · Accepted for publication in MNRAS. 18 pages, 13 figures, 1 table, plus appendices (12 pages, 7 tables 12 figures) Python functions to evaluate the equations are available at https://warwick.ac.uk/fac/sci/physics/research/astro/people/conorbyrne/byrne26_equations.py and a Fortran version is available at https://warwick.ac.uk/fac/sci/physics/research/astro/people/conorbyrne/byrne26_equations.f90

Abstract PDF $EVO ×6$STAR ×5$MTLC ×1

Astrophysics of Galaxies

Modeling the nanohertz gravitational wave background with the t-process: Improved frequentist analysis of gravitational-wave power

B. E. Moreschi, K. A. Gersbach, G. Shaifullah et al. (+2 more)

Pulsar timing array (PTA) collaborations have recently reported evidence for a gravitational wave background (GWB) signal in the nanohertz band, which most likely originates from the incoherent superposition of GWs emitted by a population of supermassive black hole binaries (SMBHBs). Since the number of binaries emitting in each frequency bin is finite, and since individual loud sources can dominate the GWB, the power spectral density (PSD) of the background is expected to deviate significantly from the smooth power law that describes an idealized population. PTA searches usually describe the PSD either with a power law or with a free spectrum model, which fits the PSD in each frequency bin as a free parameter. In this paper, we explore the t-process as a third model; it assumes a power law as the underlying spectrum but leaves each frequency bin free to deviate from it. We compare the performance of these three models on simulated datasets, injecting $100$ realizations of a realistic SMBHB population, to evaluate how well each model recovers a complex PSD. Using Bayesian and frequentist tools, we find that the t-process model gives the most precise PSD results, with uncertainties $43\%$ and $26\%$ narrower than those obtained with the power law and the free spectrum, respectively, while the improvement in accuracy is smaller. Moreover, using the t-process model, we compute isotropic and anisotropic signal-to-noise ratios with median gains of about $46\%$ over the power law and $65\%$ over the free spectrum in the first nine frequency bins. The t-process also returns lower anisotropy p-values and among the frequency bins with $p<0.01$, it allows to localize the loudest binary within the angular resolution of the sky maps in $14.3\%$ of the cases, compared to the $10\%$ for the power law and the $6.2\%$ for the free spectrum.
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All authors B. E. Moreschi, K. A. Gersbach, G. Shaifullah, S. R. Taylor, A. Sesana

Astrophysics of Galaxies

KDG 162: A Nearby Isolated Star-forming Dwarf Galaxy

Gagandeep S. Anand, Igor D. Karachentsev, Meredith J. Durbin et al. (+6 more)

The nearby dwarf galaxy KDG 162 (also known as KK 153) has recently attracted attention as a potentially gas-rich, isolated, and low-mass dwarf galaxy. However, many of these characterizations depend on the true distance to KDG 162. Here we present new Hubble Space Telescope (HST) imaging that resolves individual stars down to 3 magnitudes below the tip of the red giant branch. Using this HST imaging, we determine a distance to KDG 162 of D = 3.48 $\pm$ 0.12 Mpc, somewhat higher than previous determinations. We find KDG 162 to be relatively isolated and lying at the edge of first infall onto the M81 group. We use its stellar content to measure its recent star formation history and find that only a modest amount of star formation can be attributed to within the last $\sim$500 Myr. The present-day stellar mass outweighs the H I mass by a factor of 2$\times$. The properties of KDG 162 add to an increasingly detailed picture of nearby and isolated low-mass galaxies. In the future, deeper observations would allow for reaching more age-sensitive populations, enabling the recovery of its star-formation history back to ancient times.
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All authors Gagandeep S. Anand, Igor D. Karachentsev, Meredith J. Durbin, R. Brent Tully, Rachael Beaton, Andrew Dolphin, Serafim S. Kaisin, Lidia N. Makarova, Edward J. Shaya

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

Extreme Stellar Death and Galaxy Feedback at z = 2: A Rest-frame Ultraviolet Characterization of the Strongly Lensed Superluminous Supernova 2025wny

Willem B. Hoogendam, David O. Jones, Christopher J. Storfer et al. (+26 more)

We present photometric and spectroscopic follow-up observations of the strongly-lensed H-poor superluminous supernova (SLSN) 2025wny at $z = 2.0155$. We use integral-field Keck-II/KCWI spectroscopy to obtain rest-frame ultraviolet spectra spanning $11$ to $61$ days after maximum light. We use Pan-STARRS photometry to constrain the brightest image's magnification, finding $\mu_A=19.4\pm1.6$, a factor of $\sim$2-4 higher than mass-modeling estimates. We fit the Pan-STARRS photometry with a magnetar energy-injection model including $^{56}$Ni decay using the Modular Open Source Fitter for Transients (MOSFiT); the model can reproduce the near-maximum light curve with parameters typical of local universe SLSNe-I, including a magnetar spin period $P_{\rm spin}=4.1^{+0.7}_{-1.0}\,\mathrm{ms}$ and magnetic field $B_{\perp}=2.4^{+1.1}_{-0.8}\times10^{14}\,\mathrm{G}$; however, the late-time plateau suggests an additional power source. Spectroscopically, iron-group element line blanketing is virtually absent in the rest-frame UV spectra, and the absorption features match previously identified SLSN-I features from abundance tomography. Based on narrow ISM line metallicity estimates, SN 2025wny exploded in a sub-solar-metallicity galaxy. From host-galaxy lines in our rest-frame UV-to-optical spectrum we estimate high-velocity outflows of $\sim$575 km s$^{-1}$ and an exceptionally high Ly$\alpha$ escape fraction of $f_{esc}^{Ly\alpha}=0.23\pm0.03$. SN 2025wny matches lower-redshift SLSNe reasonably well. Upcoming surveys like LSST and Roman will discover additional high-redshift SLSNe, further testing whether SLSNe-I explosions remain consistent at the population level in the early universe.
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All authors Willem B. Hoogendam, David O. Jones, Christopher J. Storfer, Luca Izzo, Kyle W. Davis, Miranda Y. Kong, Katie Auchettl, Aadya Agrawal, David R. Aguilera-Dena, Kenneth C. Chambers, Siyuan Chen, Thomas de Boer, Ryan J. Foley, Matthew Grayling, Jason T. Hinkle, Jens Hjorth, Mark E. Huber, Chien-Cheng Lin, Thomas B. Lowe, Eugene A. Magnier, Kaisey S. Mandel, C. Tanner Murphey, Gautham Narayan, Gregory S. H. Paek, Kishore C. Patra, Haille M. L. Perkins, Armin Rest, Benjamin J. Shappee, Richard J. Wainscoat

Astrophysics of Galaxies

Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) – IV. Methyl cyanide isotopologues toward BHR71-IRS1

P. Nazari, A. Coutens, J. K. Jørgensen et al. (+16 more)

Methyl cyanide is one of the most abundant nitrogen-bearing complex organic molecules observed in the gas phase around low- and high-mass protostars. However, very few observations exist with a broad enough frequency coverage and sufficiently high sensitivity to systematically characterize its minor isotopologues toward such regions. We add to this number by analyzing data toward BHR71-IRS1 taken as part of the Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) Large Program over a ~33 GHz frequency range. We studied as many isotopologues of methyl cyanide as possible toward BHR71-IRS1. We found the column densities and excitation temperatures via spectral fitting and assuming local thermodynamic equilibrium. We then compared the derived column density ratios with those toward IRAS 16293-2422 A and B, V883 Ori, G31.41+0.31, and Sgr B2(N2b). We detect CH3CN, CH3CN $v_8$=1, 13-CH3CN, CH3-13-CN, CH3C-15-N, CH2DCN, and CHD2CN. The column density ratio of 13-CH3CN/CH3-13-CN is around unity, in agreement with previous observations. The CH2DCN/CH3CN ratios are similar for all the low-mass objects but are ~1 order of magnitude higher than those toward Sgr B2(N2b). This could be due to a warmer pre-stellar phase or a different formation timescale of Sgr B2(N2b). The D/H ratios found from methyl cyanide isotopologues agree well with those of methanol toward BHR71-IRS1, likely pointing to the formation and deuteration of methyl cyanide in a similar star-formation phase as methanol (i.e., the pre-stellar phase). We find an increase in the methyl cyanide D/H ratios with the number of deuterium atoms, which suggests that the deuterated isotopologues may form later in the pre-stellar phase. Future COMPASS studies will increase the sample size of low-mass systems with methyl cyanide analysis and potentially examine some of the trends observed here statistically.
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All authors P. Nazari, A. Coutens, J. K. Jørgensen, A. Belloche, A. L. Plunkett, S. Maret, D. Harsono, M. N. Drozdovskaya, J.-E. Lee, F. Cruz-Sáenz de Miera, J. Ferrer Asensio, M. L. R. van 't Hoff, J.-H. Jeong, Á Kóspál, B. A. McGuire, S. Spezzano, Y.-L. Yang, H.-S. Yun, S. Zeng

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

Halo Mass Function Constraints on Early Galaxy and AGN Populations in the JWST Era

Elan Yogeswaren and Robert Schaefer

The discovery by the James Webb Space Telescope (JWST) of massive galaxies and luminous active galactic nuclei (AGN) at high redshift provides an increasingly sensitive test of the connection between cosmological structure formation and the astrophysical processes that make dark matter halos observable. We develop a framework connecting the linear matter power spectrum to the mass variance, peak height, halo mass function (HMF), cumulative halo abundance, and observable galaxy and AGN populations. We use the Sheth-Tormen (ST) HMF as the baseline and compare it with an illustrative Bolshoi-Klypin-calibrated modification (KST) to quantify the sensitivity of predictions to the calibration of the HMF against cosmological N-body simulations. We apply the framework to three complementary tests: the baryonic and stellar mass reservoir available to massive galaxies, the abundance of halos capable of hosting luminous AGN, and the rest frame ultraviolet luminosity function of high redshift galaxies. Because the most massive systems occupy the rare, high peak tail of the halo distribution, modest changes in inferred host mass, baryonic conversion efficiency, black-hole occupation or duty cycle, and HMF calibration can produce large changes in predicted abundances. The ST-KST comparison shows that uncertainty in the high redshift halo population can materially affect the inferred host supply, particularly toward large z (10). Comparison with representative JWST massive galaxy, AGN, and UV luminosity function measurements demonstrates that matching the properties of an individual source is not sufficient for population consistency; the corresponding host halos must also exist in adequate numbers. Current observations provide increasingly stringent quantitative stress tests of both cosmological halo abundances and the baryonic and black hole physics at cosmic dawn.
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Astrophysics of Galaxies

Galaxy merger-driven signatures in massive black hole pair hosts across cosmic time

Pranav Satheesh, Aklant K. Bhowmick and Laura Blecha

Galaxy mergers can drive gas toward galactic nuclei, enhancing both star formation and black hole accretion in post-merger galaxies. Here we use the IllustrisTNG-50 simulation and two boxes from the BRAHMA simulation suite, all of which adopt different black hole formation models, to characterize merger-associated signatures in candidate massive black hole (MBH)-pair hosts. In all three simulations, we select post-merger galaxies whose progenitors both host MBHs and quantify their enhancements in star formation and black hole accretion relative to matched non-merging controls. In TNG50, we find substantial merger-triggered enhancements in both specific star formation rate (sSFR) and specific black hole accretion rate (sBHAR) at $0 \leq z < 3.3$, reaching $\sim 1.4\times$ and $\sim 1.5-1.7\times$ the controls, respectively. The BRAHMA runs employ more physically motivated seed formation models, seeding BHs in lower-mass galaxies and at higher redshifts than TNG50. In BRAHMA, merger-driven enhancements in sSFR and gas fractions are comparable to those in TNG50 at $z \lesssim 3.3$ and persist to the highest redshifts probed by BRAHMA ($z \sim 6$). Despite this, BRAHMA shows no significant merger-driven enhancement in sBHAR across its entire redshift range. In a similar vein, TNG50 pair hosts show an enhanced AGN fraction relative to matched controls, whereas BRAHMA shows only a weak excess among the most rapidly accreting MBHs.
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Astrophysics of Galaxies · Cross-listed from astro-ph.EP

Reflex instabilities II: The reflex motion of the central object drives at least seven instabilities in accretion discs

Nathan Magnan, Michel Tagger, Clément Baruteau et al. (+3 more)

This series of papers studies the stability of accretion discs to the reflex motion of the central object under the gravitational pull of the disc itself. In this second paper, we use linear analysis to reproduce or discover seven distinct instabilities. We outline their defining characteristics and propose a classification. Of the four instabilities that had already been discovered, three are artificial: one does not survive the transition to modern surface density profiles such as power-laws, one is due to the location of the domain's boundaries, and one is due to the use of damping layers near the domain's boundaries. Only the SLING instability of Adams et al. (1989) and the three new 'cavity' instabilities seem capable of affecting accretion discs. All four can be described to a high degree of precision by WKB methods. They may drive eccentricity growth, affect planet migration, create spiral and crescent substructures in the absence of any planet, and boost accretion onto the central object. The issue is that the three artificial instabilities are extremely hard to avoid in simulations, and would bias the same observables. This suggests that our community may not have the tools to model the reflex motion of the central object yet.
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All authors Nathan Magnan, Michel Tagger, Clément Baruteau, Aurélien Crida, Jean-François Gonzalez, Héloïse Méheut

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

Reflex instabilities I: Boundaries makes grid-based disc simulations frame-dependent

Nathan Magnan, Michel Tagger, Clément Baruteau et al. (+3 more)

If the mass distribution within an accretion disc is asymmetric, it will exert a gravitational pull on its central object. The central object must then move away from the origin of the reference frame, resulting in atypical gravitational pulls on the disc. The goal of the present series of papers is to investigate the stability of this feedback loop. In this first paper, we report a surprising finding: the choice of reference frame affects the number and nature of the waves and instabilities contained in the analytical equations. To show this, we use a simple example: the modes discovered by Sanchez et al. (2025, Appendix A.3). We provide the first analytical description of those modes, we explain their physical mechanism, and propose to call them 'bracket modes' because they arise from the bracket side of an integration by parts. We show that the same disc can be stable in the stellocentric reference frame but unstable in the barycentric reference frame. This is because the boundaries of the simulation domain are frame-dependent. To avoid this, one must model the entire disc all the way from the central cavity to the outer edge. But this is prohibitively expensive, and some discs do not have a central cavity anyway. Our results suggest that extreme caution is required when interpreting simulations of asymmetric discs, and that our community may not have the tools to model the reflex motion of the central object yet.
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All authors Nathan Magnan, Michel Tagger, Clément Baruteau, Aurélien Crida, Jean-François Gonzalez, Héloïse Méheut

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

The impact of feedback and cosmology on Cosmic Infrared Background cross-correlations

Sara Maleubre, David Alonso, Reggie Dunsdon et al. (+3 more)

We study the evolution and clustering properties of the star formation rate density (SFR) $\rho_{\rm SFR}$ in the FLAMINGO suite of hydrodynamical simulations, with the aim of exploring the possibility of constraining AGN and stellar feedback prescription, as well as the effect of cosmology, using cross-correlations between the Cosmic Infrared Background (CIB) and other tracers of the large-scale structure. Specifically, we consider tomographic measurements of the bias-weighted SFR-density $\langle b\rho_{\rm SFR}\rangle$, as well as cross-correlations between the CIB and cosmic shear as a probe of the $\rho_{\rm SFR}$-matter correlation. Most of the FLAMINGO models calibrated against the $z=0$ galaxy stellar mass function (SMF) yield similar predictions for the distribution and clustering of star-forming systems, and thus it is difficult to derive clean conclusions regarding the impact of AGN feedback or cosmology on CIB statistics. However, we show that current measurements of $\langle b\rho_{\rm SFR}\rangle$, as well as CIB-shear cross-correlations clearly disfavour models with strong stellar feedback, as well as simulations with strong kinetic (jet-driven) AGN feedback, even under the fiducial SMF calibration. This study demonstrates the potential of CIB cross-correlations to study aspects of the physics of star and galaxy formation in a cosmological setting.
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All authors Sara Maleubre, David Alonso, Reggie Dunsdon, Adrien La Posta, Amy Wayland, Joop Schaye

Astrophysics of Galaxies

The $\mathrm{[O\ III]}\lambda5007$ Equivalent Width as an Ionization-Parameter Diagnostic Across Cosmic Time

Dian P. Triani and Lisa J. Kewley

Nebular emission lines and stellar continua probe the conditions of $\mathrm{H\ II}$ regions. The optical emission line $\mathrm{[O\ III]}\lambda 5007$ is important because it is observable across a wide redshift range, enabling studies of interstellar medium (ISM) conditions across cosmic time. We investigate the equivalent width of $\mathrm{[O\ III]}\lambda 5007$ (EWO3) as an ionization-parameter diagnostic, providing an alternative to the $\mathrm{[O\ III]} \lambda 5007 / \mathrm{[O\ II]} \lambda 3727$ (O32) ratio, which requires broad wavelength coverage and dust corrections that may not be available at high redshift. We employ the MAPPINGS photoionization code with input spectra from BPASS, comparing single-star and binary-inclusive stellar populations. We find that binary-inclusive populations sustain harder ionizing spectra and strong $\mathrm{[O\ III]}\lambda 5007$ emission to later ages than single-star populations. EWO3 is highly sensitive to the ionization parameter and exhibits systematic dependencies on metallicity, gas pressure, and stellar population age. While these dependencies broadly follow those of O32, EWO3 is less sensitive to gas pressure in the low-metallicity, high-ionization regime, making EWO3 well suited for studies of metal-poor and high-redshift galaxies. Comparing the models with observations, we find that local galaxies are reproduced by lower-pressure models, whereas intermediate- and high-redshift galaxies require higher gas pressures, indicating evolving ISM conditions across cosmic time. We present metallicity- and pressure-dependent calibrations of EWO3 as an ionization-parameter diagnostic. When validated against ionization parameters derived from O32, the $\log(P/k)=6$ calibration provides the best agreement for local galaxies, while the $\log(P/k)=7$ calibration best reproduces intermediate- and high-redshift galaxies.
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Astrophysics of Galaxies · Cross-listed from astro-ph.CO

ApPolLO: Apertif counterparts of Polarised LOFAR sources

A. Berger, B. Adebahr, H. Dénes et al. (+1 more)

Knowledge of the structure and evolution of cosmic magnetic fields is indispensable to understand how primordial magnetic fields were generated and amplified during the lifetime of the Universe. Polarisation studies over significant redshift ranges are an important tool in understanding cosmic magnetic fields. We aim to understand the structure and evolution of cosmic magnetic fields, utilising the polarised spectra and depolarisation characteristics of (background) radio sources. Using radio polarisation data at two different frequencies from the LOFAR Rotation Measure (RM) grid catalogue at 144\,MHz and new Apertif data at 1.4\,GHz, we investigate the source statistics of a common sample of polarised sources, deriving the depolarisation ratio between these two frequencies. We utilise this to disentangle depolarising effects local to the source from those along the line of sight. We compile a catalogue of 598 polarised radio components, most of which are located in low-density environments. Fractional polarisation decrease for both wavelengths with redshift. We attributed the main depolarisation at 1.4\,GHz to effects occurring close to the sources, while the depolarisation measured at 144\,MHz is most likely generated by cosmic filaments along the line-of-sight. We were able to get a first redshift dependent upper limit estimate of the RM dispersion in cosmic web filaments.
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All authors A. Berger, B. Adebahr, H. Dénes, R.-J. Dettmar

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

X-ray spectral scaling of black hole mass in quasi-periodic eruptive source RX J1301.9+2747

Lev Titarchuk, Elena Seifina, Vadim Arefiev et al. (+2 more)

We present a spectral and timing analysis of X-ray emission from the actively accreting supermassive black hole (SMBH) in RX~J1301.9+2747 with prominent quasi-periodic eruptions (QPEs) using ASCA, ROSAT, XMM-Newton, and NICER observations. NICER detected renewed QPE activity from this source in 2024. We examined in detail the X-ray spectrum formation in this source during QPE outbursts applying the first-principal model, Bulk Motion Comptonization. We find an increase of the photon index $\Gamma$ with a mass accretion rate $\dot M$, the index saturation at $\Gamma_{sat}=2.7\pm 0.1$ at high $\dot M$ value during outburst peaks. Based on the derived $\Gamma-\dot M$ correlation, we apply the scaling technique for the first time to measure the black hole mass in RX~J1301.9+2747. The SMBH mass in this source was estimated to be between $4\times 10^5$ M$_ {\odot}$ and $7\times 10^6$ M$_ {\odot}$ for the inclination range from 0$^{\circ}$ to 70$^{\circ}$, which is adopted as a plausible range based on the AGN unified model assumption, applying HLX–1~ESO 243–49, OJ~287, and 1H~0707–495 as reference scaling sources. We also estimate a BH mass in RX~J1301.9+2747 applying a timing analysis, in which the Compton cloud size to be $\sim 10^{11}$ cm, estimated from the quasi-periodic oscillation frequency, $\nu\sim 10^{-4}$ Hz, indicates SMBH mass in RX~J1301.9+2747 is of order of $10^6$ M$_{\odot}$. Overall, the BH mass obtained by the scaling method in this source is consistent with previous measurements using other methods.
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All authors Lev Titarchuk, Elena Seifina, Vadim Arefiev, Diana Makhinya, Alexei Le

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

Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) II. Approach to data reduction and products for line-rich broadband (sub)millimeter spectra

Adele L. Plunkett, Sébastien Maret, Daniel Harsono et al. (+26 more)

Studying the chemical composition of the warm gas surrounding embedded solar-type protostars is one of the areas for which the Atacama Large Millimeter/submillimeter Array (ALMA) is particularly well suited. Recently, the ALMA Large Program “Complex Organic Molecules in Protostars with ALMA Spectral Surveys” (COMPASS) carried out an observing campaign of a sample of 11 protostellar regions to investigate the chemical impact of their environments and evolutionary stages. The aim of this paper is to provide the observational and procedural information necessary for the community to understand the analysis presented in forthcoming scientific papers by the COMPASS collaboration, and to enable archival research using the data products provided by our team and the ALMA Science Archive. This paper describes the technical setup of the observations, and it outlines the data-processing pipeline and primary data products from this initiative. The Common Astronomy Software Applications (CASA) was used for initial calibration following the standard ALMA Pipeline, and then IMAGER was used for self-calibration and imaging. We describe post-processing done with Python to achieve favorable continuum subtraction, correct for the primary beam response, and extract spectra. We discuss our strategy for mitigating data challenges, including those related to data volume and continuum subtraction for spectral line analysis. The incorporation of IMAGER in our workflow was advantageous in terms of the computing efficiency which allowed us to benchmark several imaging parameters and techniques; we also demonstrate that the imaging outcomes using IMAGER or CASA are scientifically comparable. Numerous data products are generated for the program, including image cubes for the 36 spectral windows targeting each source, extracted spectra, and continuum images.
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All authors Adele L. Plunkett, Sébastien Maret, Daniel Harsono, Jes K. Jørgensen, Audrey Coutens, Maria N. Drozdovskaya, Jeong-Eun Lee, Arnaud Belloche, Fernando Cruz-Sáenz de Miera, Merel L. R. van 't Hoff, Jae-Hong Jeong, Chul-Hwan Kim, Ágnes Kóspál, Martine Lützen, Brett A. McGuire, Pooneh Nazari, Silvia Spezzano, Zoie Telkamp, Yao-Lun Yang, Hyeong-Sik Yun, Audrey Andreu, Jennifer Bergner, Judit Ferrer Asensio, Niels F. W. Ligterink, Yuxin Lin, Sheng-Yuan Liu, Pierre Marchand, Mihika Rao, Shaoshan Zeng

Astrophysics of Galaxies

Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) VI. Discovery of a class I methanol maser transition and its association with acetaldehyde

Jae-Hong Jeong, Jeong-Eun Lee, Jes K. Jørgensen et al. (+16 more)

CH3OH masers that are collisionally pumped, referred to as `class I', commonly trace shock interfaces in star-forming regions, but their incidence in low-mass protostars remains poorly quantified. We use data from the COMPASS ALMA Large Program to establish the occurrence, spatial origin, and excitation of a newly detected class I CH3OH maser at 302.9 GHz towards low-mass protostars and to test whether its pumping environments exhibit signatures of shock-driven complex chemistry. COMPASS provides unbiased line surveys of 11 sources between 279.0 and 311.7 GHz at typical angular resolutions of 0.3"-0.5". Rotation diagram analysis of departures from LTE in the 302.9 GHz CH3OH excitation robustly reveals masing in seven of 11 sources, with peak brightness temperatures from a few to ~10^3 K. The brightest detection is towards HOPS 108 and is likely associated with the powerful outflow from the nearby intermediate-mass protostar HOPS 370. Excluding this case, the maser is detected in six of ten low-mass protostars (60%). All six are Class 0 sources interacting with dense ambient material, whereas the non-detections comprise three Class I sources and one isolated Class 0 core, indicating a preference for early evolutionary stages and gas-rich environments for outflow-ambient medium interactions. The maser emission is spatially coincident with thermal CH3OH along outflow cavity walls and bow shocks, but is more compact and knot-like. Among the surveyed COMs, only CH3CHO closely traces the shocked morphology of the 302.9 GHz maser, and only around HOPS 108. These results show that class I CH3OH masers in low-mass protostellar systems are more prevalent than previously recognised and preferentially occur in younger, more embedded sources. More sensitive CH3CHO observations are needed to test whether a similar relationship with shock-driven chemistry also applies in the low-mass regime.
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All authors Jae-Hong Jeong, Jeong-Eun Lee, Jes K. Jørgensen, Audrey Coutens, Maria N. Drozdovskaya, Adele L. Plunkett, Arnaud Belloche, Sébastien Maret, Hyeong-Sik Yun, Fernando Cruz-Sáenz de Miera, Daniel Harsono, Merel L. R. van 't Hoff, Chul-Hwan Kim, Ágnes Kóspál, Brett A. McGuire, Pooneh Nazari, Silvia Spezzano, Yao-Lun Yang, Shaoshan Zeng

Astrophysics of Galaxies

Early galactic heavy element production - a phenomenological approach

B. Wehmeyer, D. Blaschke, F.K. Röpke et al. (+1 more)

The high abundances of heavy elements in early, extremely metal-poor stars is still an unsolved issue in Galactic Chemical Evolution (GCE). Standard approaches, such as mergers of neutron stars, have several difficulties, and several non-merger production channels are under discussion. Here, we suggest that pre-enriched inflow might explain the heavy elements seen in low metallicity stars in the Galaxy. To characterize the conditions of the origin of such a pre-enriched infall, we apply a heavy-element freeze-out approach. We characterize the initial distribution by Lagrange parameters which are nonequilibrium generalizations of temperature and chemical potentials. We then speculate about the origin of such a pre-enriched infall: The required nonequilibrium conditions might be found in cosmological fluctuations in the early Universe, and might be connected to the formation of primordial black holes.
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All authors B. Wehmeyer, D. Blaschke, F.K. Röpke, G. Röpke

Astrophysics of Galaxies

Chaotic accretion can (still) explain early supermassive black hole growth

Kastytis Zubovas and Matas Tartėnas

The origin of supermassive black holes (SMBHs) is still debated, with hypotheses ranging from massive seeds to super-Eddington growth to chaotic accretion. Recent discoveries of very high redshift SMBHs constrain their possible origin and growth scenarios. We investigate whether the chaotic accretion scenario can explain the most extreme high-redshift SMBH masses. We predicted the exponential growth timescale of black holes accreting chaotically in a slowly-spinning dark matter halo, in which uncorrelated gas inflows maintain a low spin and hence a low radiative efficiency. We compared this prediction against the growth timescales and seed masses implied by a compilation of all known SMBH mass estimates at $z>7$ and against the feeding and feedback conditions expected in such haloes. We found that in the period $7.6 < z < 10.6$, the most massive SMBHs likely grew very efficiently, with an exponential growth timescale $\tau \sim 32$~Myr, which is consistent with chaotic accretion predictions provided that growth was almost continuous. All high-redshift SMBHs with virial mass estimates could have grown from seeds with $M_{\rm seed} \lesssim 100 \, \msun$. We describe the evolution of the mass reservoir feeding such a black hole, suggesting that wind-driven feedback eventually removes most of the gas and changes the growth mode of black holes at $z \sim 7.5$. We make several predictions regarding the spins, host-galaxy correlations, and observable counterparts of high-redshift SMBHs that distinguish our model from its alternatives. These predictions will be testable in the near future. Chaotic accretion from stellar-mass seeds remains a viable origin for the earliest known SMBHs, without invoking massive seeds or super-Eddington growth.
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Astrophysics of Galaxies

Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS): I. Overview of the ALMA Large Program

J. K. Jørgensen, A. Coutens, M. N. Drozdovskaya et al. (+27 more)

It remains a fundamental research question in astrochemistry to characterize the inventory of complex organic molecules formed during the early stages of star formation, which may affect the eventual chemical composition of protoplanetary disks and potentially planets. The Atacama Large Millimeter/submillimeter Array (ALMA) provides the angular resolution and sensitivity to zoom in on the hot (T > 100 K) gas surrounding embedded solar-type protostars and chart their molecular inventories with high accuracy. The ALMA Large Program Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) aims to provide comprehensive inventories of the molecular content of a sample of protostellar sources to understand the chemical impact of their environments and evolutionary stages. COMPASS is an unbiased spectral survey of 11 line-rich Class 0 and I protostellar sources in the spectral range from 279.0 to 311.7 GHz at 0.15-0.5" angular resolution with ALMA, corresponding to the inner ~100 au (radius) around the targeted sources. This paper provides an overview of the COMPASS program and the adopted strategy in terms of observational setups and targeted sources. We also present a qualitative comparison of the spatial distributions of selected molecules and the relative strengths of the line fluxes of selected complex organics. The qualitative comparisons suggest that chemical differences between sources may be present, for example, between the abundances of groups of oxygen- and nitrogen-bearing species, but also that such variations occur at levels smaller than an order of magnitude. Quantitative comparisons of abundances at these levels require the large bandwidth of the survey, as well as a careful analysis of the excitation and strengths of the several thousands of lines detected toward each source in the survey, as will be explored in forthcoming papers.
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All authors J. K. Jørgensen, A. Coutens, M. N. Drozdovskaya, J.-E. Lee, A. L. Plunkett, S. Maret, A. Belloche, D. Harsono, Z. Telkamp, F. Cruz-Sáenz de Miera, M. L. R. van 't Hoff, Á Kóspál, M. Rao, J. Bergner, J.-H. Jeong, S. Spezzano, B. A. McGuire, P. Nazari, Y.-L. Yang, H.-S. Yun, A. Andreu, J. Ferrer Asensio, C.-H. Kim, N. F. W. Ligterink, Y. Lin, S.-Y. Liu, M. Lützen, P. Marchand, C. Xue, S. Zeng