Astrophysics of Galaxies
Binary-lens amplification of starlight: from magnification flares to quasi-periodic tracking of orbital evolution
Hanxi Wang, Bence Kocsis and Miguel Zumalacárregui
Supermassive black hole binaries (SMBHB) are expected at the center of
galaxies as a result of
galaxy mergers. The dynamics and
evolution of SMBHBs shed light on the
evolution and formation of
galaxies, the gravitational wave background and the nature of
gravity. Many methods have been proposed to identify sub-parsec SMBHBs via the detection of gravitational waves or the modulation of the emission from the surrounding gaseous environment. In a previous study, we proposed a new method of identifying SMBHBs in non-active galactic
nuclei via gravitational
lensing. The caustics, i.e. the source positions with a divergent magnification, exhibit a complex extended geometry which rotates with the binary period. Each caustic-crossing produces an extreme magnification by up to a factor of $10^{6}$. In this work, we generalize the previous study and describe the rich phenomenology of binary-lens amplification of starlight (BLAST). We explore the electromagnetic transients produced when accounting for the relative proper motion of the source, either a single or a binary
star, the eccentricity and precession of the SMBHB, and the relative inclination. Systems where a
star rapidly drifts across the caustic produce a single- or double-peaked
flare. In the opposite limit, a
star with no relative proper motion produces quasi-periodic lensed starlight (QPLS), i.e., repeated peaks that track the system's orbital
evolution. We determine the expected magnification and peak duration in different circumstances, and calculate the magnification curves and their
Fourier transforms. This study may help construct search pipelines to identify SMBHBs in electromagnetic time-domain surveys.
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Astrophysics of Galaxies · Cross-listed from astro-ph.HE
Can bosenovae deplete the galactic dark matter?
Samuel Gómez Gómez and Joshua Eby
No: neither through the bosenovae of gravitational atoms formed around
stars and compact objects, nor through those of
boson stars formed in the galactic dark-matter
halo. We assume that all the dark matter consists of ultralight
bosons with attractive self-interactions, which can be captured in the gravitational potential of astrophysical objects or condense into self-gravitating configurations. When these systems collapse in a bosenova, part of their mass is turned into relativistic radiation that escapes the
galaxy. We bound the mass that a single object can eject and sum it over realistic models of the Milky Way and of other types of
galaxies. For gravitational atoms, with realistic stellar populations and stellar
evolution, the
stars of the Milky Way deplete at most $\epsilon^{\rm GA}_\star\simeq3\times10^{-9}$ of its
halo, and the pump is equally negligible in other
galaxies. The central black hole, Sgr A$^*$, could reach $\epsilon^{\rm GA}\sim10^{-3}$, but only for a
boson mass disfavoured by ultrafaint dwarf
galaxies and beyond the validity of the perturbative treatment, where only a
geometric bound on the dark matter flux is available. For
boson stars feeding on the rest of the
halo, these would radiate at most $\sim3\times10^{-5}$ of the Milky-Way
halo and $0.1\%$ of a DF2-like one.
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Astrophysics of Galaxies
A Step-Like Transition Underlying the Life and Death of Galaxies
Zhicheng He, Enci Wang, Luis C. Ho et al. (+6 more)
How
galaxies stop forming
stars is a complex and central problem in astrophysics. Numerous physical mechanisms have been proposed, yet a simple, unified framework connecting these mechanisms remains lacking. Here, we derive a step-function quenching response from the fundamental principle of gas mass conservation, governed by the competition between gas-supply and gas-depletion timescales. This response also enables the gas-supply timescale to be inferred from the observed quenched fraction. Applying this method to approximately 350,000
galaxies, we find a characteristic gas-supply timescale of ~1 Gyr, reveal distinct inside-out and outside-in quenching signatures associated with supermassive black holes and dark matter
halos, respectively, and identify
galaxies with intermediate stellar surface mass densities as occupying a critical state for quenching and rejuvenation. Our work establishes a unified physical framework in which a simple step-function response captures how diverse physical processes regulate
galaxy quenching and the resumption of
star formation through their effects on the competition between gas-supply and gas-depletion timescales.
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All authors Zhicheng He, Enci Wang, Luis C. Ho, Yingjie Peng, Huiyuan Wang, Yong Shi, Tao Wang, Yongquan Xue, Tinggui Wang
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
A Parsec-Scale Transient High-Frequency-Peaked Radio Source in the Very Large Array Sky Survey Brightening and Fading over a Decadal Timescale
Yuyang Chen, B. M. Gaensler, Maria R. Drout et al. (+10 more)
A subset of active galactic
nuclei (AGN) manifests as compact
radio sources with peaked
radio spectra, commonly referred to as peaked-spectrum (PS) sources. Generally, PS sources are interpreted as young
radio jets, but the early
evolution of the jet is rarely observed and not fully understood. Here, we present VT J182357-234511 (VT J1823-2345), a
radio transient in the Very Large Array Sky Survey (VLASS) that resembles a PS source. Notable properties of VT J1823-2345 include: (i) brightening by a factor of 3 between 1996 and 2021 at 1.4 GHz, (ii) peaked spectra with high frequency peaks at $\nu_{\mathrm{p,obs}}\gtrsim6\,\mathrm{GHz}$, (iii) a peaked 3 GHz light curve that has been fading since 2023, (iv) a resolved Gaussian (major-axis) size of 0.4 mas in 2024, and (v) a linear polarization fraction $p_{\mathrm{L}}\simeq0.73\%$ at 8.8 GHz with an extreme Faraday rotation measure $\mathrm{RM_{\mathrm{obs}}} \sim +12,000\,\mathrm{rad}\,\mathrm{m}^{-2}$. On the sky, VT J1823-2345 coincides with a
supernova remnant and an F-type
star, but no background
galaxy is seen. Based on the multi-wavelength properties, we disfavor Galactic transients, explosive extragalactic transients, and blazar variability as plausible explanations. We argue that VT J1823-2345 is consistent with a "short-lived" parsec-scale PS source with a decades-old jet that does not grow into a large-scale
radio galaxy. From comparing the full VLASS light curves, we speculate that VT J1823-2345 is similar to many VLASS nuclear transients reported in the literature, which may represent an emerging class of transient
radio jets, perhaps related to episodic AGN activity or jetted tidal disruption events.
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All authors Yuyang Chen, B. M. Gaensler, Maria R. Drout, Dillon Z. Dong, Emmanuel Momjian, Tracy Clarke, Wendy Peters, Emil Polisensky, Ariel D. Amaral, Katie Auchettl, Ylva Götberg, Kovi Rose, Peter Senchyna
Astrophysics of Galaxies
The contact frontier in Galactic civilization networks: radial structure and the Galactic habitable zone
Kohji Tsumura
The probability of interstellar contact depends not only on the abundance of technological civilizations but also on their spatial connectivity. Treating civilizations as nodes linked whenever their separation is smaller than the distance a signal travels within a communicative lifetime, we determine the radial structure of Galactic civilization networks. An exponential stellar disc replaces the uniform disc of earlier work, and the fraction of
stars hosting civilizations may vary with radius as a Galactic Habitable Zone (GHZ). The isolation, contact and network transitions are frontiers several kiloparsecs wide, not boundaries: the contact frontier is set entirely by the disc scale length, and the network frontier, broadened by gradient percolation, stays near 1.5 scale lengths. The two frontiers overlap over a band containing the Sun, where both transitions proceed at once. Within this factorized GHZ model, the radius of peak civilization density depends only logarithmically on the strength of
supernova sterilization, and the wide range of published peak radii, from the Galactic centre to 12 kpc, is reproduced primarily by varying that one parameter. Under the present normalization, the location of the zone has only a modest effect on the local contact probability, whereas the modelled Galactic connectivity is minimized when the civilization-density peak lies near the solar Galactocentric radius, where current determinations place the peak.
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Astrophysics of Galaxies
IRAC-Excess Galaxies in the NIRSpec Wide Survey: physical properties of bright EELGs at $z\sim7$ and implications for Reionization
Katherine Ormerod, Renske Smit, Joris Witstok et al. (+4 more)
We present an analysis of 23 Spitzer/IRAC excess
galaxies at $5.66 < z < 7.64$, observed as part of the NIRSpec Wide GTO survey. With NIRSpec PRISM spectroscopy, we measure a median rest-frame [OIII]$+\rm{H}\beta$ EW $=1583$~Å, consistent with predictions from the pre-JWST selection and we identify $17/23$ $(\sim74\%)$ of our sample as extreme emission line
galaxies (EELGs), based on a selection of [OIII]$+\rm{H}\beta$ EW $\geq1000$~Å. The typical EELG is powered by
star-formation rather than active galactic
nuclei (AGN) based on their line widths, line ratios and absence of high-ionization lines, though we cannot exclude an AGN contribution in a few individual sources. We find that our luminous ($\langle M_\mathrm{UV}\rangle=-20.7$) EELG sample is characterised by sub-solar
metallicities $(7.38 < \rm 12 + \log(O/H) < 8.12)$, young stellar populations ($t_\star \sim 20$ Myr), and enhanced ionizing
photon production efficiencies, with median $\log_{10}(\xi_\mathrm{ion}/\mathrm{erg}^{-1}~\mathrm{Hz}) = 25.62$. We find that more UV luminous ($\sim L_\mathrm{UV, z=7}^\ast$) EELGs exhibit systematically lower O32 ratios than fainter ($\sim 0.1\times L_\mathrm{UV}^\ast$) EELGs at fixed [OIII]$+\rm{H}\beta$ EW, indicating less extreme radiation fields and/or lower gas densities than their fainter counterparts. Furthermore, bright EELGs exhibit low neutral hydrogen column densities, consistent with a scenario in which they have largely ionized their circumgalactic medium (CGM). Despite this, we find very low Lyman-$\alpha$ escape fractions ($<2$%), suggesting these systems reside in relatively small ($\lesssim 0.25$~pMpc) ionized regions of the intergalactic medium (IGM), possibly suggesting that bright
galaxies have a minor contribution to reionization.
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All authors Katherine Ormerod, Renske Smit, Joris Witstok, Anna de Graaff, Michael V. Maseda, Andrew J. Bunker, Chris Willott
Astrophysics of Galaxies
The ringing Large Magellanic Cloud: evidence for a recent dwarf-dwarf collision
Slater J. Oden, Bethany Garver, Joshua Povick et al. (+2 more)
Galaxy interactions are ubiquitous in the Universe and represent a primary pathway for
galaxy growth. Close passages of dwarf
galaxies can induce large-scale vertical oscillations in stellar disks, a phenomenon first identified in the Milky Way within the past decade. Here, we use recent red clump distance maps of the Large Magellanic Cloud (LMC) to show that its stellar periphery is vertically offset from the central disk plane by $\sim$1.2 kpc at radii of $\sim$8.5 kpc and exhibits an S-shaped warp reaching $\sim$3.6 kpc at $\sim$11.5 kpc. We compare these observations to an $N$-body simulation of the LMC-Small Magellanic Cloud (SMC) system, in which a direct collision between the Clouds excites vertical oscillations in the outer LMC disk with amplitudes of $\sim$1~kpc and a period of $\sim$600~Myr. The simulated disk best matches the observed vertical structure $\sim$260~Myr after the collision, although this timing depends on the adopted LMC model. At that time, the simulation reproduces the sign and radial onset of the observed offset and the orientation of the warp, but underpredicts the amplitude of the warp by a factor of $\sim$4-5. These results support a collision-driven origin for the large-scale vertical structure of the LMC disk and demonstrate that dwarf–dwarf interactions can reshape stellar disks on galactic scales.
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All authors Slater J. Oden, Bethany Garver, Joshua Povick, David L. Nidever, Victor P. Debattista
Astrophysics of Galaxies
Constrain the Size of Broad Line Region in NGC 1068 Using Sub-millimeter Excess
Qi Guo, Junzhi Wang, Lingrui Lin et al. (+3 more)
Constraining the size of broad-line region (BLR) close to the
accretion disk in active galactic
nuclei (AGNs) is key to understand the central engine and
evolution of AGN. We propose a new method to constrain the BLR size, based on millimeter to sub-millimeter spectral energy distribution (SED), from which a sub-millimeter excess may be found. Such excess can be used to determine the solid angle of the free-free emission region from BLR, as a region with high electron density and optically thick at sub-millimeter wavelength for free-free continuum. Millimeter to sub-millimeter SED analysis toward the central source S1 in a nearby type II AGN NGC 1068 was done, which gave an upper limit on the solid angle of BLR region as(4.94 +/- 0.61) *10^-6 arcsec^2, corresponding to a radius no more than 0.085 pc. Such a constraint on the BLR size is important for estimating the masses of central supermassive black holes in AGNs.
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All authors Qi Guo, Junzhi Wang, Lingrui Lin, Yuqiang Li, Zhi-yu Zhang, Fengyao Zhu
Astrophysics of Galaxies
Uncovering the origin of complex velocity distributions in edge-on disc galaxies
Sophie Townson, Marie Martig, Robert J. J. Grand et al. (+3 more)
Stellar line-of-sight velocity distributions are a powerful tool for studying
galaxy kinematics and formation history, with multiple-peaked LOSVDs often indicating the presence of complex kinematic components. We extract stellar LOSVDs across the disc of a simulated spiral
galaxy viewed edge-on, and study how often and why we see multiple-peaked LOSVDs. We find that the multiple-peaked LOSVDs are mainly found close to the midplane because they result from the presence of spiral arms. This is not because the spiral arms have significantly different kinematics to the disc, but because they correspond to over-densities. Variations in the number of arms present along a line-of-sight create variations in the number of peaks in LOSVDs. This can be used to quantify the strength of the spiral arms above the midplane, and how the thickness of spiral arms vary across the disc. We find that the commonly used fourth order Gauss-Hermite moment, $h_4$, is negative in the regions where there are multiple-peaked LOSVDs, and hence traces spiral arms. Finally, we discuss the observability of the multiple-peaked regions and their associated $h_4$ measurements with current integral field spectrographs. We find that the spectral resolution of MUSE might not be high enough to uncover multiple peaks in LOSVDs when they result from spiral arms, but should allow for identification of the regions of negative $h_4$. On the other hand, higher resolution spectrographs like KOALA and WEAVE may be able to recover multiple peaks in LOSVDs, representing a promising avenue for characterising spiral arms in edge-on disc
galaxies.
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All authors Sophie Townson, Marie Martig, Robert J. J. Grand, Prashin Jethwa, Jesús Falcón-Barroso, Timothy A. Davis
Astrophysics of Galaxies · Cross-listed from astro-ph.SR
Nova shells in 3D: I. A catalog of integral field spectroscopic observations
Janis B. Rodríguez-González, Edgar Santamaría, Martin A. Guerrero et al. (+1 more)
Classical novae eject material during thermonuclear eruptions on accreting white dwarfs, forming expanding shells whose structures and kinematics provide insights into the eruption mechanism and binary interaction. However, their intrinsic three-dimensional (3D) structures remain poorly constrained. We present the first 3D catalog of nova shells based on integral field spectroscopy, enabling us to investigate their structures beyond projection effects. We compiled observations of 19 nova shells obtained with MUSE at the VLT, complemented by new MEGARA observations at the GTC and WEAVE observations at the WHT. We constructed 3D visualizations of selected emission lines to explore the diversity of shell morphologies and kinematics. The shells reveal a wide variety of structures, including ellipsoidal or spherical shells, rings, bipolar features, and clumpy or irregular components, many of which are not apparent in 2D projections. Approximately 60% of the sample exhibits predominantly ellipsoidal or spherical shapes, while about 30% shows ring-like or bipolar structures. Several objects display strong line-dependent morphological differences, with [O III] or [N II] tracing distinct kinematic components from those seen in H${\alpha}$. Compared with imaging studies, integral field spectroscopy reveals a larger fraction of bipolar or toroidal shells. The differences between emission lines highlight the diverse excitation mechanisms and physical conditions within the ejecta. Finally, comparing expansion velocities in the plane of the sky and along the line of sight suggests low intrinsic aspect ratios, consistent with estimates from projected shell shapes.
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All authors Janis B. Rodríguez-González, Edgar Santamaría, Martin A. Guerrero, Jesús A. Toalá
Astrophysics of Galaxies
Galactic Morpholography: Linking present-day galaxy compactness to assembly history and relic formation in the COLIBRE simulations
Maximilian Zemsch, Claudia D.P. Lagos, Chiara Spiniello et al. (+11 more)
Compactness is widely used to identify candidate relic
galaxies, the largely untouched survivors of the first compact massive
galaxies. Yet relicness is an evolutionary rather than structural property. Using the COLIBRE cosmological hydrodynamical simulations, we test whether present-day structure traces
galaxy formation and assembly histories. Six complementary tracers (stellar age,
metallicity, [Mg/Fe], sSFR, velocity dispersion and ex-situ mass fraction) vary coherently across the stellar mass-size plane and independently identify a characteristic compactness scale of $\log_{10}(\Sigma_{1.5,\mathrm{crit}}/(\mathrm{M}_\odot\mathrm{kpc}^{-1.5}))=9.75\pm0.10$. We term this mapping between present-day structure and assembly history morpholography. Combining this threshold with the Degree of Relicness ($\mathrm{DoR}>0.6$), which quantifies early and rapid
star formation, we distinguish compact from ancient
galaxies and identify 267 relic candidates at their intersection. Ancient
galaxies span nearly the full ex-situ-fraction range, from predominantly in-situ formation to substantial merger-driven growth. Relic candidates are concentrated at stellar masses of $\approx 10^{10}$-$10^{11}$ solar masses, host black holes that lie $\approx 0.25$-$2.5$ dex above the median black-hole-stellar-mass relation, and are predominantly satellites (76%), preferentially in cluster environments. Only $\approx 3$% show evidence of strong tidal stripping, suggesting that environment primarily preserves rather than creates relic-like systems. Approximately one third (87/267) are direct descendants of the $z=2$ massive quiescent
galaxies identified in COLIBRE. Present-day structure thus retains a statistical fossil record of assembly history, supporting morpholography as a link between nearby
galaxies and the early Universe.
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All authors Maximilian Zemsch, Claudia D.P. Lagos, Chiara Spiniello, Michele Cappellari, Ángel Chandro-Gómez, Katy L. Proctor, Evgenii Chaikin, Johanna Hartke, Filip Huško, Sylvia Ploeckinger, Alexander J. Richings, Mahsa Sanati, Joop Schaye, James W. Trayford
Astrophysics of Galaxies
The physical and chemical structure of TMC-1. The spatial distribution and excitation conditions of carbon, oxygen, and sulfur bearing species: Depletion of CO and CS
J. Cernicharo, B. Tercero, N. Marcelino et al. (+3 more)
We present a detailed study of the physical and chemical structure of TMC-1 from the observed spatial distribution of HC3N, NNH+, CN, and their isotopologues, the O-bearing species C18O, C17O, CH3OH, CH3CHO, and H2CO, and the S-bearing species CS, HCS+, H2CS, and H2CCS. The well known filamentary structure of TMC-1 can be interpreted as a single cloud with a velocity gradient perpendicular to the filament, or less likely as due to the
alignment of three independent clouds in the line sight with velocities of 5.3-5.7, 5.7-5.9, and 5.9-6.3 km/s. The main contribution to the emission of all studied C-bearing species is found at 5.83 kms/s. We conclude that the three velocity components are dynamically connected and that C-bearing molecules show a different behavior of their abundances compared to O-bearing species, which have emission peaks at 5.7 and 6.25 km/s, and appear at different spatial locations than cyanopolyynes and CnH and CnN radicals. The detection of 13C18O, with exactly the same line profile than that of C18O and C17O, excludes the possibility that the decrease of their emission at 5.83 km/s, could be due to self absorption or absorption by a foreground cloud component. Hence, as indicated by the spatial distribution of C18O and C17O, CO is significantly depleted at the velocities and positions where the emission of the carbon chains and radicals is found. This suggests that the emission of O-bearing species is coming from the external layers of the carbon-rich filaments. A comparison between S-bearing species and other molecules indicates that CS, CCS, HCS+, and H2CS are significantly depleted in the zone of CO depletion. A clear increase of the deuteration of several molecular species is found in the zones where CO and CS are depleted.
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All authors J. Cernicharo, B. Tercero, N. Marcelino, G. Esplugues, G. Molpeceres, M. Agúndez
Astrophysics of Galaxies
The Role of Environment in Shaping the Assembly Timelines of Massive Quiescent Galaxies at Cosmic Noon
Tianmu Gao, J. Trevor Mendel, Letizia Bugiani et al. (+10 more)
JWST observations of massive quiescent
galaxies (MQGs) at $z\sim2$ have revealed diverse
star formation histories (SFHs). In this letter, we investigate whether these variations are linked to the environment in which MQGs reside, as quantified by the host dark matter
halo mass. We identify 12 MQGs from a representative sample of
galaxies at $1.6<z<3.5$ obtained by the Blue Jay survey, a JWST Cycle 1 program, and infer their SFHs via modelling of the deep NIRSpec medium-resolution spectra along with multi-band photometry. By correlating the formation and quenching epochs of individual MQGs with their respective host
halo masses from the 3D-HST survey, we find that after accounting for the
redshift range of the sample ($1.8<z<2.5$), MQGs in more massive
haloes formed at significantly earlier
cosmic epochs. Meanwhile, although these
galaxies also quenched earlier overall, the scatter in quenching epochs across similar
halo masses indicates that the quenching process likely involves other contributing factors and is not solely determined by
halo mass.
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All authors Tianmu Gao, J. Trevor Mendel, Letizia Bugiani, Minjung Park, Sirio Belli, Joel Leja, Claudia del P. Lagos, Amir H. Khoram, Rebecca L. Davies, Razieh Emami, Gabriel Maheson, Anita Zanella, Benjamin P. Collins
Astrophysics of Galaxies
Sleeping or Dead? Probing the Quenching Mechanism of JWST Dormant Galaxies at z > 3 with ALMA
Mengyuan Xiao, Songnan Qi, Pascal A. Oesch et al. (+16 more)
JWST has revealed a population of "dormant”
galaxies at z>3 with strong Balmer breaks and weak emission lines, whose
star formation appears to have declined only recently. Whether these
galaxies are undergoing a lasting transition toward quiescence or merely experiencing a temporary suppression of
star formation remains unclear. We investigate their molecular gas content using archival ALMA observations of [CII]158um and CO rotational transitions. Starting from all publicly available JWST/NIRSpec prism observations and using joint spectrophotometric fitting, we construct a parent sample at z>3 and log(Mstar/Msun)>9.5 in the ALMA-accessible COSMOS, UDS, and GOODS-South fields. Our final sample comprises 7 dormant
galaxies and 15 quiescent
galaxies with ALMA constraints on their molecular gas content (mostly 3 sigma upper limits). We find that dormant
galaxies exhibit systematically lower
star formation rates averaged over the past 10Myr (SFR10Myr) than over the past 100Myr (SFR100Myr), supporting a recent rapid decline in their
star formation. For the ~70% of the sample with sufficiently constraining ALMA observations, their molecular gas fractions lie at least ~0.3-2dex below those expected for main-sequence
galaxies. Moreover, the molecular gas fractions of dormant
galaxies show no systematic difference from those of quiescent
galaxies in our sample. This indicates that dormant
galaxies have already reached a gas-poor state shortly after quenching and favors a scenario in which the rapid shutdown of
star formation is associated with depletion or removal of the molecular gas reservoir, rather than primarily with suppressed
star formation efficiency while retaining a substantial molecular gas reservoir. Our results suggest that, if no substantial gas replenishment occurs in the future, dormant
galaxies are more consistent with becoming "dead” than with being temporarily "sleeping”.
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All authors Mengyuan Xiao, Songnan Qi, Pascal A. Oesch, Longji Bing, Miroslava Dessauges-Zavadsky, Andreas L. Faisst, Mahsa Sanati, Rashmi Gottumukkala, Gabriel Brammer, David Elbaz, Robert Feldmann, Yoshinobu Fudamoto, Lucas C. Kimmig, Benjamin Magnelli, Rui Marques-Chaves, Anurag Amol Sawarkar, Sune Toft, Francesco Valentino, Christina C. Williams
Astrophysics of Galaxies
PDRs4All XXIII. JWST-MIRI template spectra of PAHs in the Orion Bar obtained with blind signal separation
P. Amiot, O. Berné, J. Roux-Morin et al. (+12 more)
The aromatic infrared bands (AIBs) are observed in a wide variety of astrophysical sources, and now in unprecedented detail by the James Webb space
telescope (JWST). These bands are generally attributed to the emission from polycyclic aromatic hydrocarbon (PAHs). Our aim is to extract mid-infrared AIB template spectra from JWST observations of the Orion Bar photo-dissociation region that can be used to derive PAH properties from observations of other objects. We used the JWST MIRI-MRS observations from the PDRs4All program. We first isolated the AIBs from the data using a multi-component fitting approach. We then applied a non-negative
matrix factorization to the isolated AIB spectra and extracted two templates, named AIBirrad and AIBshield following previous work. The spatial distribution and spectral characteristics of these two spectra suggest that they originate from two chemical distinct populations. We interpret AIBirrad as emission originating from a PAH population strongly exposed to ultra-violet (UV) radiation and mainly composed of large, compact ionized PAHs. Conversely, AIBshield is interpreted as originating from a more shielded population of PAHs, which is less exposed to the UV by being more embedded in the cloud. This population consists of small, asymmetric and mainly neutral PAHs with bonded aliphatic side groups. These templates can serve to analyze PAH emission in a wide variety of objects observed with MIRI-MRS.
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All authors P. Amiot, O. Berné, J. Roux-Morin, I. Schroetter, C. Boersma, A. Fuente, J. R. Goicoechea, E. Habart, A. Maragkoudakis, T. Onaka, E. Peeters, M. Robberto, A.G.G.M Tielens, D. Van De Putte, S. Vicente
Astrophysics of Galaxies · Cross-listed from astro-ph.HE
Black Hole Binary Mergers in Galactic Nuclei: Combined Effects of Secular Dynamics and Stellar Flybys
Hao Wang, Bin Liu and Johan Samsing
Galactic
nuclei, with the central supermassive black holes (SMBHs) and surrounding dense
star clusters, serve as natural laboratories for studying gravitational dynamics in extreme gravitational environments. In this work, we model the long term
evolution of black hole binaries (BHBs) in these environments by incorporating the tidal influence of the central SMBH, the potential of the nuclear
star cluster, SMBH induced relativistic precession, and
stochastic perturbations from stellar flybys. Our numerical simulations show that the long term
evolution of BHBs is predominantly governed by the SMBH-driven ZLK mechanism. However, once stellar flybys are included, they can modify both the binary angular momentum and energy. The cumulative effect of repeated flyby encounters substantially reshapes the long term dynamical
evolution, eventually leading systems toward either merger or disruption. Based on a population synthesis study, we find that this combined secular and non-secular channel produces a merger rate of approximately $\mathcal{R}\simeq16\mathrm{Gpc^{-3}yr^{-1}}$, which is significantly higher than the rates predicted by dynamical channels that neglect stellar flybys. Furthermore, we predict that a non-negligible fraction of merging systems would retain detectable eccentricities at low frequencies around 5 Hz, thus providing a distinctive observational signature for next generation ground based GW detectors. Our results demonstrate that the
stochastic perturbations from the surrounding environment are essential for modeling BHB
evolution in galactic
nuclei, and that this channel may contribute a major fraction of observed mergers.
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Astrophysics of Galaxies · Cross-listed from astro-ph.CO
specwizard: A Public Python Framework for Creating Synthetic Absorption Spectra from Hydrodynamical Simulations
Andrés Arámburo-García, Tom Theuns, Joop Schaye et al. (+1 more)
We present specwizard, a publicly available modular Python package for generating synthetic absorption spectra from hydrodynamical simulations. The code combines atomic data from the National Institute of Standards and Technology database with ionisation fractions computed using the cloudy spectral synthesis code for multiple ionising backgrounds, enabling consistent modelling of bound–bound and bound–free absorption for resonant transitions of all ions. specwizard employs a column-density–conserving projection scheme, includes natural line broadening for the Lyman series, and offers optional treatments of instrumental resolution and noise for direct comparison with high-resolution
quasar spectra. As example applications of the code, we shoot sightlines through the eagle cosmological simulation to generate a z = 3.2 synthetic
quasar spectrum containing H i Lyman-series transitions, including damping wings and Lyman-limit absorption. Additionally, we compute metal-absorption lines probing the circumgalactic medium of simulated
galaxies, and investigate the correlated absorption of H i and Si iii. We demonstrate that specwizard applied to outputs from eagle accurately reproduces key observational diagnostics of the Lyman-alpha forest, including the
redshift evolution of the mean transmission, the transmission PDF and the transmission power spectrum. We take advantage of the fact that the eagle simulation also reproduces the measured
evolution of the temperature-density relation to infer the
evolution of the amplitude of the ionizing background, finding excellent agreement with recent theoretical models and measurements.
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All authors Andrés Arámburo-García, Tom Theuns, Joop Schaye, Alexey Boyarsky
Astrophysics of Galaxies
A heterogeneous set of unusual quasars selected from astrometry and broad-band photometry
C. Cheng, K. Valeckas, L. Christensen et al. (+7 more)
The aim of this study is to explore methods for how to identify new
quasars with different properties with regard to reddening,
redshift, the presence of broad absorption lines from outflows, or other rare properties affecting the broad-band colours. We use Gaia-based astrometric pre-selection to study only sources that have zero parallax and zero proper motion within errors. We subsequently match these sources with information from wide-area photometric surveys and build colour-colour diagrams. Based on these diagrams we select targets for follow-up spectroscopy. In the subsequent analysis we also apply observations from SPHEREx to firmly establish
redshifts. We secure spectroscopic observations for 24 sources. Of these, three are found to be
stars and the remaining 21 are classified as
quasars spanning a
redshift range from z=0.139 to z=3.732. The majority of the sources located away from the normal
quasar locus in colour-colour diagrams are found to be broad-absorption-line
quasars. A single source, the lowest
redshift source at z=0.139, is reminiscent of the so-called Little Red Dots found at high
redshifts with JWST. Using the simple procedure followed here it is possible to locate previously undiscovered
quasars with interesting properties, in particular Broad Absorption Line
quasars and
quasars with unusual extinction.
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All authors C. Cheng, K. Valeckas, L. Christensen, A. Henderson de la Fuente, L. Fuglsang, V. Vuolteennaho, Pyykkinen, R. H. Rasmussen, S. Bijavara Seshashayana, J. P. U. Fynbo
Astrophysics of Galaxies
Strong gravitational lensing with Euclid
Alessandro Sonnenfeld
Euclid data is going to lead to the discovery of approximately 10^5 new strong gravitational lenses, thereby increasing the number of known lenses by a factor of 30. Such an impressive jump has the potential to revolutionise the field of strong
lensing, by covering an ever-increasing range in the parameter space occupied by the lenses and lensed sources, and by uncovering rare and precious strong lens systems. The first quick data release of Euclid has already revealed hundreds of lenses, giving us a taste of what the final Euclid strong lens sample might look like. These lenses include a variety of objects acting as deflectors, from isolated
galaxies to clusters, from early-type
galaxies to edge-on disks. As many as four double-source plane lenses, in which one foreground object lenses two
galaxies at two different
redshifts, have already been discovered. As more data are acquired, it might become possible to detect the strong
lensing signature of dwarf
galaxy satellites, and to find lenses with an unusually large number of images. In this paper, we try to anticipate the kind of discoveries that these data will bring along.
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Astrophysics of Galaxies
Large dust grains escaping from a supernova remnant
Evgenii O. Vasiliev
Dust grains produced in the
supernova (SN) ejecta at early ages are partially destroyed in hot gas of the SN remnant. Large grains owing to their inertia can overtake the forward shock front of the remnant and move through the ambient interstellar medium. Using one-dimensional gas dynamics including the dust destruction we study the transport of dust grains inside the SN remnant and the ambient medium. Here we estimate the surviving and escaping mass fractions depending on the cut-off (maximum) size in a power-law distribution of grain sizes. We found that these fractions follow closely each other at late age of the SN remnant, i.e. almost all grains, which have survived in the remnant, leave it for the ambient interstellar medium. At the age of 30 kyr – the onset of the radiative phase with density $n\sim 1$ cm$^{-3}$ with solar
metallicity – the escaping/surviving mass fractions for the cut-off size of several microns reach about $0.7-0.8$. The major part of these grains have size larger than $1~\mu$m and initially located at distances $\gtrsim 0.2$ of the ejecta core radius. Later dust grains at velocity of several hundreds km/s escaping the remnant continue to be destroyed due to kinetic sputtering in the interstellar medium. Grains with sizes of several microns are destroyed marginally and therefore will survive in the interstellar gas. After decelerating of grains in the medium the surviving mass fraction of grains produced in the SN remnant, which evolves in an ambient gas with $n$ from 1 to 100 cm$^{-3}$, is from $\sim 0.5$ to $\sim 0.3$, respectively, for the cut-off grain size $a_{cut} = 10~\mu$m. A decrease of the cut-off size in the distribution results in lower surviving mass fraction.
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Astrophysics of Galaxies · Cross-listed from astro-ph.IM
Identifying Planetary Nebulae Candidates from IPHAS and VPHAS+ Surveys via YOLO Deep Learning Models
Titouan Sérandour, Anne-Laure Méalier, Bruno Colicchio et al. (+5 more)
We present a deep learning detection method capable of effectively identifying planetary nebulae (PNe) on IPHAS and VPHAS+ surveys. Our detection pipeline is based on the YOLO architecture and is adaptable to other
datasets. Using the HiPS system, we preprocess and augment the $r$, $i$, and $H{\alpha}$ bands to produce two red, green, and blue (RGB) image
datasets: (1) $640 \times 640$ px images at full resolution, and (2) $1 280 \times 1 280$ px images designed to capture extended objects up to $0.2$ deg. Images of $\sim 2600$ PNe are labelled using the HASH database. The loss function and evaluation metrics are adapted to the diffuse and low-contrast nature of PNe; a very low intersection over union (IoU) threshold ($1\%$) is used. A $k$-fold cross validation shows that the YOLOv12m model achieves an average precision of $0.979$ on the first
dataset. At a confidence threshold of $0.15$, it achieves a precision rate of $98.7\%$ and a recall rate of $97.4\%$. We deployed our system (on $1280 \times 1280$ images) on the full surveys' coverage ($\sim 3755$ deg$^2$), and present a preliminary analysis of the detection results. The system is robust against artifacts such as CCD corner defects and HiPS tile joints. Our convolutional-neural-network-based model achieved excellent results on the test set, comparable to-or exceeding-that of a recent Swin
Transformer approach. However, a challenge persists when applying deep learning models to extensive and densely populated Galactic fields: the development of an automated system that can effectively discriminate PNe from mimics that human experts are able to distinguish (e.g., H II regions). We outline possible improvements for future work.
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All authors Titouan Sérandour, Anne-Laure Méalier, Bruno Colicchio, Dominique Daniel, Philippe Gilberton, Philippe Oros, Thomas Boch, Djaffar Ould Abdeslam
Astrophysics of Galaxies
Microcaustics: Fast GPU-Accelerated Dynamical Microlensing of Time-Dependent Extended Sources
Joshua Fagin, Connor Stone, James Hung-Hsu Chan et al. (+7 more)
Gravitational microlensing probes unresolved
quasar accretion disc structure and compact objects in lens
galaxies and is an important systematic in strong-lens time-delay cosmography. Most analyses use static microlensing map simulations because evolving individual microlenses and caustics is computationally prohibitive. We present Microcaustics, a GPU-accelerated Python package built on PyTorch for dynamical microlensing of time-dependent extended sources in strong gravitational lenses. It combines a local-exact/far-field deflection solver, source-directed lens-plane scouting with temporal reuse, and biquadratic inverse polygon mapping (IPM). GPU batching and fused Triton rasterization accelerate the calculation, while binary caustic labels track source-centred crossings. Across three simulated quadruply lensed
quasar systems, our package generates a 10-year, 147-frame multiband light curve in an amortized median of 0.68 s (0.88 s with labels) on a consumer GPU with a median light-curve RMSE of 0.35 mmag, while recovering every reference source-centred caustic crossing. At comparable map accuracy, the batched throughput is 780 times higher than that of a recent CUDA IPM implementation and extrapolates to a speedup of millions relative to classic GPU-D. We demonstrate that our IPM converges as $N_{\rm ray}^{-0.84}$, approaching the idealized $N_{\rm ray}^{-1}$ convergence rate of piecewise-affine IPM and improving upon the $N_{\rm ray}^{-1/2}$ inverse ray-shooting rate. We also introduce a GPU-resident general relativistic and reverberating
quasar source model and demonstrate our method with an evolving
supernova source. These advances make fully dynamical stellar fields practical for
Bayesian and simulation-based inference.
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All authors Joshua Fagin, Connor Stone, James Hung-Hsu Chan, Sophia Miskiewicz, Henry Best, Paras Sharma, Matthew O'Dowd, Laurence Perreault-Levasseur, Yashar Hezaveh, Simon Birrer
Astrophysics of Galaxies
Barflow: Modeling Gas Kinematics of Bar-Driven Flows
Seungwon Baek, Woong-Tae Kim, Taehyun Kim et al. (+2 more)
We present self-consistent $N$-body/hydrodynamical simulations of isolated, Milky Way-like
galaxies with stellar and gaseous disks. By varying the initial gas fraction, we find that gas delays bar formation and, in the most gas-rich model, suppresses it by exciting higher-order spiral modes and promoting early central mass growth. Once a bar forms, continued gas inflow and gravitational torques weaken the bar and inhibit its secular slowdown, keeping bars in the gas-bearing models shorter and predominantly in the fast-bar regime, while the gas-free bar evolves into the slow-bar regime.
Stars and gas respond differently to the same barred potential. While the mean stellar velocity field is well described by a smooth bisymmetric pattern, the cold and warm gas follow elongated, $x_1$-like streamlines with sharp shock-induced velocity transitions, producing sawtooth-like radial and archlike tangential velocity profiles. Despite these strong noncircular motions, their azimuthally averaged tangential velocities closely follow the circular velocity over most of the disk. By contrast, the hot gas is dominated by stellar feedback and thermal pressure and is largely decoupled from the ordered bar-driven flow. To describe these bar-driven gas flows, we introduce the barflow model, a phenomenological description of non-sinusoidal gas streaming motions with a radially varying shock-front phase. Mock line-of-sight velocity-fitting experiments show that the barflow model recovers the intrinsic rotation curve, bar-driven velocity perturbations, and radial gas transport more accurately than the conventional bisymmetric model.
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All authors Seungwon Baek, Woong-Tae Kim, Taehyun Kim, Dajeong Jang, SungWon Kwak
Astrophysics of Galaxies
Simulations of Dust Content and Attenuation in $z=5-15$ Galaxies
Dhruv T. Zimmerman, Jed McKinney, Desika Narayanan et al. (+10 more)
Correctly modeling the dust attenuation law in
galaxies is essential to properly inferring their growth and physical properties. With the rapid discovery of $z>6$
galaxies by JWST and lack of constraints on the properties of dust at these
redshifts, we must turn to theoretical models to predict the properties of dust at these
redshifts. In this paper, we develop a theoretical foundation for the nature of high-
redshift attenuation laws. We analyze $107$ cosmological zoom-in simulations of
galaxies run with the SMUGGLE
galaxy formation model. SMUGGLE includes an explicitly modeled multiphase interstellar medium and a state-of-the-art dust model with a self-consistently evolving dust grain size distribution. We forward model these simulations with the radiative transfer package POWDERDAY to produce synthetic spectra and attenuation curves for a set of $z=5-15$, $M_*\sim10^{6.5}-10^{10}\; \mathrm{M}_{\odot}$
galaxies. We find evidence for flatter attenuation curves than the commonly used locally-calibrated literature attenuation laws assumed when modeling high-
redshift galaxies. The vast majority of our attenuation curves also lack the 2175 Angstrom absorption feature. Our attenuation laws do not evolve strongly over $z=15-5$, which we attribute to relatively constant fractions of small grains up to $z=4$ in our simulations. We present a set of simulation-informed priors on dust attenuation law parameterization that could be implemented in SED fitting codes. There is an anti-correlation between
galaxy mass and attenuation curve slope and positive correlation between
galaxy mass and $A_V$, which we attribute to dust growth becoming efficient in our massive
galaxies with $\log{M_*/\mathrm{M}_{\odot}}\gtrsim9$ and with ISM conditions above a critical
metallicity threshold.
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All authors Dhruv T. Zimmerman, Jed McKinney, Desika Narayanan, Caitlin M. Casey, John Chisholm, Alex M. Garcia, Michelle C. Jecmen, Jessica Kelley-Derzon, Federico Marinacci, Julian B. Muñoz, Laura V. Sales, Ethan Savitch, Paul Torrey
Astrophysics of Galaxies
Large-scale Environmental Dependence of AGN Activity Revealed by JWST Pa$\alpha$ Emitters
Danyang Jiang, Linhua Jiang, Shuqi Fu et al. (+7 more)
The role of the large-scale environment in regulating AGN activity remains an open question. We investigate the Mpc-scale environments of 70 AGNs at $z=1.1$-$1.5$ using a highly complete sample of 3,419 Pa$\alpha$ emitters with accurate spectroscopic
redshifts from JWST slitless spectroscopic survey. This
dataset allows us to robustly trace the environments and quantify the environmental dependence of AGN properties. We measure the eighth-nearest-neighbor surface density of Pa$\alpha$ emitters around each AGN, probing $\sim$1.5 pMpc scale environments. We find that this environmental density exhibits a weak positive correlation with
radio luminosity.
Radio-bright AGNs tend to reside in statistically denser environments than their
radio-faint counterparts. The environmental density also has a positive correlation with the Eddington ratio and a weak negative correlation with the central black hole mass, implying more efficient black hole
accretion in dense environments. We construct Pa$\alpha$ luminosity functions (LFs) in AGN environments and find that they are systematically elevated relative to the field Pa$\alpha$ LF. In addition, their faint-end slopes are shallower, suggesting accelerated
galaxy growth and enhanced quenching of
star formation. As Pa$\alpha$ emitters trace gas-rich,
star-forming
galaxies, our results support a scenario in which the large-scale cold gas promotes AGN activity at
cosmic noon.
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All authors Danyang Jiang, Linhua Jiang, Shuqi Fu, Zijian Zhang, Jie Chen, Chenxi Bao, Yihe Wang, Junya Arita, Darshan Kakkad, Jan-Torge Schindler
Astrophysics of Galaxies
Hot Molecular Hydrogen in Galaxies at Redshift ~ 0.2-1.5 Revealed by JWST
Jie Chen, Linhua Jiang, Shuqi Fu et al. (+5 more)
Molecular hydrogen (H$_2$) is the fundamental component of the molecular gas reservoir that fuels
star formation and black hole growth. While prominent hot H$_2$ emission ($\gtrsim 1000$ K) has been explored in nearby
galaxies, its excitation mechanisms at higher
redshifts remain poorly constrained. We present a systematic study of hot molecular gas traced via ro-vibrational H$_2$ emitters at z~0.2-1.5 using JWST slitless spectroscopy. Exploiting JWST's great sensitivity to near-infrared H$_2$ ro-vibrational transitions such as H$_2$ 1-0 S(1), we build a sample of 144 H$_2$-luminous
galaxies and characterize their multi-wavelength properties. About 96.5% and 80% of these
galaxies are detected in the
radio and far-infrared (FIR) bands, respectively, and their hot H$_2$ emission strongly correlates with the
radio and FIR radiation. Based on
radio excess, X-ray emission, and optical diagnostics, 62 sources (43%) exhibit significant AGN activity. The H$_2$ line luminosities of the sample show a sublinear dependence on
radio luminosity, while the relation between the H$_2$ luminosities and total infrared luminosities is approximately linear after excluding the
radio-excess sources. These scaling relations suggest that
star formation provides a baseline contribution to hot H$_2$ excitation, while
radio-excess sources require an additional contribution from AGN-related processes such as jet- or wind-driven shocks. These results reveal a multi-channel excitation scenario and shed new light on the interplay between
star formation, AGN activity, and the interstellar medium during
galaxy evolution.
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All authors Jie Chen, Linhua Jiang, Shuqi Fu, Zijian Zhang, Danyang Jiang, Jing Wang, Ran Wang, Darshan Kakkad