arXiv subjects

F. Combes

Publications and source records attributed to F. Combes.

At least 19 recordsLinked to original sources

arXiv2026

Metal-poor molecular clouds in dwarf galaxies at parsec-scale resolution

Understanding how stars form at low metallicity is challenging because carbon monoxide (CO) emission, which usually probes the molecular gas reservoir, is faint, and tends to be concentrated in parsec-scale clumps. To overcome this difficulty, in order to study the molecular clouds in metal-poor environments, we have acquired CO(2-1) ALMA maps at 3-4 pc resolution of four nearby dwarf galaxies with nebular (O/H) metallicities ranging from roughly 1/9 Z_sun to 1/3 Z_sun. Significant CO signal in the cubes has been identified through two masks, a ``strict'', high-confidence, mask and a ``broad'' one for better completeness. The former traces the cores of the clouds, while the latter includes fainter emission in the vicinity of the cores. Through a cloud-finding algorithm applied to the two sets of masked cubes, we have identified more than 200 molecular clouds across the sample, with roughly 50 in NGC3109, at 1/9 Z_sun, the lowest metallicity parsec-scale cloud population yet observed. The best-fit size-linewidth relations for the resolved clouds are similar among all galaxies, with a slope like the Milky Way (MW), but with lower velocity dispersion at a given cloud size. For a fixed CO-to-H_2 MW conversion factor, the cloud virial ratios tend to be large, and show a weak increasing trend with increasing cloud size, and decreasing apparent surface densities and metallicity. We find evidence for faint but significant CO emission outside CO-bright cores, spanning similar velocities to those observed in the cores. We attribute this to effective shielding by gas and dust, despite the low metallicities of our sample, since the CO tends to be cospatial with dust as traced by far-infrared emission.

astro-ph.GA↗

arXiv2026

A MUSE Study of Stellar and Ionized-Gas Kinematics in Central Group Galaxies

Understanding gas accretion and feedback in low-mass galaxy groups bridges the gap between isolated ellipticals and cluster-dominant galaxies. We present new Multi Unit Spectroscopic Explorer (MUSE) observations of 17 nearby brightest group galaxies (BGGs), revealing diverse origins for their gas reservoirs. Warm ionized gas, traced by Halpha and [N II], is detected in 77% (13/17) of the sample, with morphologies including rotating disks with or without tails and diffuse emission, rings, and filaments. Unlike brightest cluster galaxies, most BGGs host regularly rotating stars, whereas their gas displays diverse kinematics. Nearly half of the rotating gas disks are aligned with the stars, consistent with internal recycling. However, tails, diffuse emission, or rings in three aligned systems may retain signatures of past accretion or interactions. The remaining disks, ring-like structures, and most filamentary systems are misaligned, supporting gas acquisition through mergers, interactions, or halo cooling. Compact disks are consistent with centrally concentrated, low-angular-momentum gas, possibly linked to residual cooling. Most filamentary systems lie near the precipitation threshold (tcool/teddy ~ 1-2) and preferentially occupy the turbulence-dominated region of the k-plot, supporting condensation consistent with chaotic cold accretion. All galaxies with detected X-ray halos, including those without warm gas, exhibit low central entropies (<30 keV cm^2) and short central cooling times (<3 Gyr). These conditions alone cannot predict multiphase gas, suggesting that AGN- or interaction-driven perturbations and turbulence-induced thermal instabilities help regulate condensation. No single mechanism dominates: BGGs are transitional systems in which internal recycling, environmental accretion, and cooling-driven condensation coexist, linking isolated ellipticals to cluster-dominant galaxies.

astro-ph.GA↗

arXiv2026

A ${}^{13}$CO Detection in a Massive Molecular Gas Flow in Abell 1795's Central Galaxy

We present new ALMA ${}^{13}$CO(2-1) observations of the central galaxy in the cool-core cluster Abell 1795, targeting the origin of extended molecular filaments. The filaments extend for 5--7 kpc and are closely drawn up around large radio bubbles inflated by jets from the central active galactic nucleus (AGN). Smooth velocity gradients along their lengths are consistent with entrained flows lifted by the expanding bubbles. Here we detect the northern molecular filament in the low-opacity molecular tracer ${}^{13}$CO(2-1), which can provide a more reliable measure of the molecular gas mass and conditions than ${}^{12}$CO. The velocity structure in ${}^{13}$CO(2-1) is consistent with that of the ${}^{12}$CO(2-1) emission. Using a range of plausible excitation temperatures and covering fractions, we thereby determine a filament molecular gas mass of (0.1--2) $\times \ 10^9 \ \text{M}_\odot$, or down to an order of magnitude below previous estimates. This implies a CO-to-H$_2$ conversion factor of $α_\text{CO} =$ 0.4--5 $\ \text{M}_\odot $ (K km s$^{-1}$ pc$^2)^{-1}$ in the filament, or $\sim$ 0.1--1 times the standard assumption of the Milky Way value. Direct entrainment by the N radio bubble is now plausible, as it can provide sufficient mechanical energy and buoyant support for the molecular gas flow. Similarly, measured X-ray cooling rates are also now consistent with in-situ condensation of uplifted, low-entropy hot gas. Both formation mechanisms require multiple generations of bubbles at higher filament masses.

astro-ph.GA↗

arXiv2026

AGN Feeding and Feedback: Resolving the Torus

Active Galactic Nuclei (AGN) play a key role in galaxy evolution by regulating star formation within their host galaxies. It is therefore crucial to understand how the central supermassive black holes (SMBH) are fueled by material from the galactic disk, and how AGN feedback impacts the surrounding gas. Most information so far comes from very nearby active galaxies (z < 0.008; D < 35 Mpc), providing the best spatial resolution and revealing randomly oriented dusty molecular tori that fuel SMBHs. A facility such as ALMA2040, offering significantly higher sensitivity and better angular resolution than current ALMA, would enable progress in two fundamental areas that remain beyond the capabilities of all existing and planned observatories: (i) probing the dynamics of the material feeding the AGN down to the accretion disk in nearby galaxies; and (ii) spatially resolving the tori and circum-nuclear regions of more energetic and cosmologically significant AGN, such as local quasars (z ~ 0.1 and Lbol > 10^45 erg/s).

astro-ph.IM↗

arXiv2026

Virgo Filaments VII: MeerKAT HI-imaging of the VirgoIII filament

We present MeerKAT HI observations of galaxies in the nearby Virgo III filament. At a median distance of $\sim30$ Mpc, the filament extends over $\approx16$ Mpc across $\sim56$ deg$^2$. Our survey comprises 15 targeted MeerKAT pointings centred on HI deficient galaxies. Multi-resolution HI imaging at 8-90 arcsec with an rms of $\sim0.3$ mJy beam$^{-1}$ reaches column densities of $\sim4\times10^{20}$ to $\sim4\times10^{18}$ atoms cm$^{-2}$. This probes HI in galaxy discs at $\sim1.2$ kpc resolution and their outskirts at $\sim13.5$ kpc. We detect HI emission from 80 sources within the 500-3000 km/s range; most are optically detected galaxies, while 10 per cent lack confirmed counterparts. We also identify three HI clouds without optical counterparts near an interacting system, possibly displaced during the interaction. Galaxies in the filament lie below the field HI gas-fraction scaling relations at fixed stellar mass. Crucially, $\sim40$ per cent of galaxies not selected for HI deficiency fall more than $1σ$ below these relations, with an even greater fraction lying under the mean relation itself, indicating that the low HI gas fractions are widespread in the filament rather than confined to the pre-selected deficient population. Quantifying HI morphologies using an asymmetry parameter, we find a wide range of disturbances without a clear trend with projected distance to the filament spine or local density, suggesting a combination of local interactions and the filament itself. This paper presents the survey description, catalogue, and HI atlas enabling investigations of gas removal mechanisms in Virgo III galaxies.

astro-ph.GA↗

arXiv2026

Young star clusters in the extended UV disk of M83

The process of star formation in a low-metallicity environment and whether it differs from star formation in the solar neighbourhood is an open topic. Recently, CO clumps were identified within the extended ultraviolet (XUV) disk of M83 despite the low metallicity and distance from the galaxy center which allows a search for any recent star formation in the clumps. We aim to probe whether active star formation is occurring within the CO clumps in the XUV disk, and to assess its implications for star formation in such environments. We analyse deep Subaru Suprime-Cam Halpha, Hyper Suprime-Cam g, r, & i, and Gemini/FLAMINGOS 2 J and Ks band imaging to search for evidence of star formation within the ALMA-identified CO clumps. We identify sources within the CO clump contours, and we evaluate the probability that these sources are associated with the CO clumps rather than being chance alignments. Based on their magnitudes and adopting single-age stellar population models, we estimate their masses. Four of the clumps have an associated near-infrared counterpart. Based on their magnitude, color, and the general source density in the field, two of these could be chance alignments. One counterpart is associated with the most massive clump in the sample, while another is an unresolved cluster near-infrared source with an estimated age of 5 Myr and a mass of 2000 Msun. The other, an extended complex, is consistent with an age of 6Myr and a mass of 700Msun. The near-infrared photometry is sensitive to young clusters with masses down to a few hundred of Msun for a fully sampled IMF. Star formation is ongoing in a few of the CO clumps, and despite their location on the outskirts of M83, favourable conditions for star formation persist in at least a few clusters. One of the detected sources appears to be interacting with an adjacent molecular clump, which could trigger further star formation.

astro-ph.GA↗

arXiv2026

HI 21-cm absorption in low- and high-excitation radio-loud AGNs at $z<0.5$ from MALS

We present results from a search of cold neutral gas associated with radio-loud active galactic nuclei (AGNs) at $z < 0.5$ using HI 21-cm absorption measurements from the MeerKAT Absorption Line Survey (MALS). Cross-matching the MALS 1006 MHz and SDSS DR18 catalogs yields 1908 radio sources at $z < 0.5$. Of these, 613 are classified as AGNs using BPT diagnostics and radio luminosity criteria. We further classify 426 AGNs into 327 low-excitation radio galaxies (LERGs) and 99 high-excitation radio galaxies (HERGs). We observe a significant ($>3σ$) difference in $k$-corrected $g-r$ color, consistent with LERGs residing in older galaxies with quenched star formation. We searched a radio-bright subsample of 79 LERGs and 20 HERGs ($S_{\mathrm{1.4\,GHz}} > 4$ mJy) for associated HI 21-cm absorption. This spans six decades in radio luminosity ($\log L_{\mathrm{1.4\,GHz}}$ (WHz$^{-1}$) $\sim 21.1-27.0$), probing an order of magnitude fainter than previous targeted HI surveys. We report five new detections (4 LERGs, 1 HERG) at $0.29 < z < 0.47$. The overall detection rate of $3^{+3}_{-2}$% (at a $3σ$ threshold of 10.0 kms$^{-1}$) is consistent with sensitivity-matched low-$z$ ($<0.2$) samples, suggesting no significant redshift evolution out to $z \sim 0.5$ or dependence on radio luminosity. Evaluating velocity offset, asymmetry, and width reveals three systems with entirely redshifted absorption and two with predominantly blueshifted absorption. HI profiles in LERGs show diverse asymmetries and velocity offsets exceeding 350 kms$^{-1}$, indicating disturbed cold-gas kinematics likely driven by lobe expansion or jet activity.

astro-ph.GA↗

arXiv2026

The GECKOS survey: Resolving the molecular and ionised gas in the galactic outflow of ESO~484-036

We present a spatially resolved, multiphase study of the outflow in the edge-on starburst galaxy ESO~484-036 from the GECKOS survey, combining VLT/MUSE H$α$ and ALMA CO(1$-$0) observations to analyse the atomic ionised and cold molecular gas. Both show extraplanar emission consistent with a conical outflow. Ionised gas is enclosed by molecular gas, which is detected up to 2.5 kpc from the disc. Molecular gas dominates near the disc, except at the nuclear base, while ionised gas extends beyond 3 kpc. The deprojected outflow velocities are $\lesssim400\ \rm km\ s^{-1}$ in both phases and are consistent with ballistic motion, with some gas possibly falling back onto the disc. We find that the mass outflow rates are in the range of $\dot M_{\rm ion}\sim1-5\ \rm M_\odot\ \rm yr^{-1}$ and $\dot M_{\rm mol}\sim13-54\ \rm M_\odot\ \rm yr^{-1}$, giving mass loading factors of $η_{M\rm, ion}\sim 0.1-0.6$ and $η_{M\rm, mol}\sim 1.5-6.2$. These ranges reflect velocity and geometric uncertainties. Despite the short depletion time ($τ_{\rm dep} = 16-48\rm\ Myr$), the outflow may regulate rather than permanently quench the gas reservoir. Energy loading ($η_E\leq0.16$) and momentum loading ($η_p\lesssim1$) support a purely starburst-driven outflow. Comparing ESO~484-036 with a literature sample, we find a systematic 1~dex shift in mass-loading relations when molecular gas is included. This produces a $\sim3.5$~dex discrepancy with cosmological simulations in $η_{M\rm, mol}/η_{M\rm, ion}$, implying that current models strongly underpredict cold gas production and the role of short-range recycling flows in starburst galaxies.

astro-ph.GA↗

arXiv2026

Virgo Filaments VI: H$α$ clumps in the filaments around the Virgo galaxy cluster

It is still not clear which environmental processes operate in filaments. Given the ubiquity of filaments and their importance in feeding clusters, a proper understanding of these mechanisms is crucial to a more complete picture of galaxy evolution. To investigate them, we need large galaxy samples with spatially resolved information. As part of this effort, we analyse resolved H$α$ maps of 685 galaxies inside and outside the filaments around the Virgo cluster in addition to extensive measurements of integrated physical properties. We create a pipeline to decompose the H$α$ images into individual clumps that trace star forming regions. We find that the number and average size of clumps in a galaxy are well-defined functions of distance and angular resolution. In particular, the power-law relation between the number of clumps and the distance of a galaxy is consistent with a fractal structure of star forming regions. We formulate an algorithm to compare filament and non-filament galaxies after removing observational differences. Although we do not have any conclusive evidence for a difference in clump size distributions between filament and non-filament galaxies, we do find that filament galaxies have slightly more peripheral clumps than their non-filament counterparts.

astro-ph.GA↗

arXiv2026

The Galaxy Activity, Torus, and Outflow Survey (GATOS): N. Unveiling physical processes in local active galaxies. Unsupervised hierarchical clustering of JWST MIRI/MRS observations

With the rise of the integral field spectroscopy, we are currently dealing with large amounts of spatially resolved data, whose analysis has become challenging, especially when observing complex objects such as nearby galaxies. We aim to develop a method to automatically separate different physical regions within the central parts (1"~160 pc, on average) of galaxies. This can allow us to better understand the systems, and provide an initial characterisation of the main ionisation sources affecting its evolution. We have developed an unsupervised hierarchical clustering algorithm to analyse data cubes based on spectral similarity. It clusters together spaxels with similar spectra, which is useful to disentangle between different physical processes. We have applied this method to a sample of 15 nearby (distances <100 Mpc) galaxies, 7 from the Galaxy Activity, Torus, and Outflow Survey (GATOS) and 8 archival sources, all observed with the medium resolution spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) on board of the JWST. From the clusters, we computed their median spectrum and measured the line and continuum properties. We used these measurements to train random forest models and create several empirical mid-IR diagnostic diagrams for the MRS channel 3 wavelength range, including among others the bright [Ne II], [Ne III], and [Ne V] lines, several H2 transitions, and PAH features. The clustering technique allows to differentiate emission coming from an AGN, the disc, and star forming regions in galaxies, and other composite regions, potentially ionised by several sources simultaneously. This is supported by the results from the empirical diagnostic diagrams, that are indeed able to separate physically distinct regions. This innovative method serves as a tool to identify regions of interest in any data cube prior to an in-depth analysis of the sources. [abridged]

astro-ph.GA↗

arXiv2026

YOLO-CIANNA: Galaxy detection with deep learning in radio data: II. Winning the SKA SDC2 using a generalized 3D-YOLO network

As the scientific exploitation of the Square Kilometre Array (SKA) approaches, there is a need for new advanced data analysis and visualization tools capable of processing large high-dimensional datasets. In this study, we aim to generalize the YOLO-CIANNA deep learning source detection and characterization method for 3D hyperspectral HI emission cubes. We present the adaptations we made to the regression-based detection formalism and the construction of an end-to-end 3D convolutional neural network (CNN) backbone. We then describe a processing pipeline for applying the method to simulated 3D HI cubes from the SKA Observatory Science Data Challenge 2 (SDC2) dataset. The YOLO-CIANNA method was originally developed and used by the MINERVA team that won the official SDC2 competition. Despite the public release of the full SDC2 dataset, no published result has yet surpassed MINERVA's top score. In this paper, we present an updated version of our method that improves our challenge score by 9.5%. The resulting catalog exhibits a high detection purity of 92.3%, best-in-class characterization accuracy, and contains 45% more confirmed sources than concurrent classical detection tools. The method is also computationally efficient, processing the full ~1TB SDC2 data cube in 30 min on a single GPU. These state-of-the-art results highlight the effectiveness of 3D CNN-based detectors for processing large hyperspectral data cubes and represent a promising step toward applying YOLO-CIANNA to observational data from SKA and its precursors.

astro-ph.GA↗

arXiv2026

Projection Effects in Barred Galaxies Causing Wrong Interpretation of Radial Flows

Galaxy disks in rotation are sometimes the site of radial flows, especially in their gas component. It is important to estimate the outflows, due to AGN or supernovae feedback, or inflows due to bar gravity torques. However, these radial flows may be confused with non-circular motions, which are quite frequent in the center of galaxy disks. We use a simulated giant, barred spiral galaxy from the GalMer database to study the non-circular motions induced by the bar. Our goal is to identify the spurious radial flows that kinematics modeling algorithms can detect, assuming circular orbits for the gas. Using mock data of a strongly barred galaxy, we quantify the radial velocities computed by the 3D-Barolo algorithm for different disk inclinations and several bar orientations in the plane of the sky: along the major and minor kinematic axes and at 45° from them. Our results show that projection effects cause kinematics modeling algorithms to confuse the radial component of velocity due to elliptical orbits with significant radial flows with mean values up to 92 km.s$^{-1}$, within the bar region. The computed rotation curve is also wrongly estimated inside the bar region, by as much as 150 km.s$^{-1}$ for the highest inclination.

astro-ph.GA↗

arXiv2026

The GECKOS Survey: Extraplanar ionised gas in star-forming galaxies from eDIG to galaxy-scale winds

We map the extraplanar gas, with $\sim$50-200 pc resolution, in nine star-forming galaxies using Multi-Unit Spectroscopic Explorer (MUSE) observations from the GECKOS VLT Large Program targeting edge-on galaxies with similar stellar mass as the Milky Way. The narrow range in stellar mass ($\pm0.35$ dex) of the GECKOS sample makes it ideal for studying trends with star formation rate (SFR). We find strong extraplanar emission reaching $\sim$2-8 kpc from the disk midplane in all targets with $\rm{SFR}\geq$1 M$_{\odot}$ yr$^{-1}$. Targets with SFR$\,\geq\,$5 M$_{\odot}$ yr$^{-1}$ have brighter, more extended H$α$ emission compared to lower SFR targets. In high-SFR systems, the gas velocity dispersion ($σ_{\rm Hα}$) shows a biconical morphology, consistent with the expectation of outflows. This agrees with previous works suggesting high velocity dispersion in a biconical shape is a good means to identify outflows. We find mixed results using line diagnostics ([OIII]$_{5007}$/H$β$ - [NII]/H$α$ and $σ_{\rm Hα}$ - [SII]/H$α$) to spatially resolve ionisation mechanisms across the extraplanar gas. The highest [NII]/H$α$ are the extraplanar gas of the highest SFR systems, yet main-sequence galaxies have the highest [OIII]/H$β$. While the morphology of [NII]/H$α$ may be useful to identify outflows, the absolute value of the line ratio alone may not distinguish strong outflows from extraplanar gas of main-sequence galaxies. The ubiquitous extraplanar emission can be interpreted as the result of feedback, in the form of large-scale winds for starbursts or smaller-scale galactic fountains for main-sequence galaxies. Moreover, shock-heating may ionise gas at the interface of the disk and the circumgalactic medium, independent of the source of the gas.

astro-ph.GA↗

arXiv2025

A sub-ppm upper limit on the cosmological variations of the fine structure constant alpha

Absorption spectroscopy toward high-redshift quasars provides strong constraints on the putative variation of fundamental constants of physics on cosmological time scales. The submillimeter ground-state transitions of methylidyne (CH) and water (H2O), both molecules widespread and coeval in the interstellar medium, provide a sensitive test for variations of alpha, the fine structure constant, and mu, the proton-to-electron mass ratio, taking advantage of the unmatched spectral resolution and frequency reliability of radio techniques. We used ALMA simultaneous observations of the two species to constrain any velocity offset between their absorption profiles toward the radio-bright lensed quasars PKS1830-211 (z_abs=0.88582) and B0218+357 (z_abs=0.68466). Our observational setup minimizes instrumental errors and known sources of systematics, such as time variability of the absorption profile and frequency-dependent morphology of the background quasar. The excellent correlation between CH and H2O opacities, the large number of individual narrow velocity components, and the number of independent spectra obtained due to the intrinsic time variability of the absorption profiles ensure that even the chemical segregation bias is minimized. We obtained bulk velocity shifts delta_v = -0.048 pm 0.028 km/s and -0.13 pm 0.14 km/s (1 sigma confidence level) between CH and H2O in the direction of PKS1830-211(NE) and B0218+357(SW), respectively. These values convert into the 3sigma upper limits |Delta_alpha/alpha| < 0.55 ppm and 1.5 ppm, respectively, taking into account the independent upper limits on |Delta_mu/mu| previously obtained for these systems. These constraints on |Delta_alpha/alpha|, at look-back times of about half the present age of the Universe, are two to four times deeper than previous constraints on any other single high-z system.

astro-ph.CO↗

arXiv2025

High resolution mapping of molecular tori with ALMA

Recent high resolution mapping of the circum-nuclear regions of Active Galactic Nuclei (AGN) has revealed the existence of geometrically thin nuclear disks, in general randomly oriented with respect to their galaxy hosts. These molecular tori have typical radii of 10~pc, and contain a few 10$^7$ M$_\odot$ of H$_2$, with H$_2$ column densities between 10$^{23}$ and 10$^{25}$ cm$^{-2}$. We mapped two of the most massive of these molecular tori with higher resolution, in order to unveil their morphology and kinematics, their possible warp and clumpiness, and derive their stability and life-time. We used the highest resolution possible with ALMA (16~km baseline) in Band 7, taking into account for mapping CO(3-2) and HCO$^+$(4-3) the compromise between sensitivity and resolution. New features are discovered at the high resolution, obtained with a beam of 0.015\arcsec, equivalent to $\sim$ 1~pc scale, at their $\sim$ 15~Mpc distance. The molecular torus in NGC~613 appears like a ring, depleted in molecular gas near the center. The depletion region is displaced by 3~pc toward the NW from the AGN position, meaning some $m=1$ asymmetry in the torus. The molecular torus in NGC~1672 has a different position angle from previous lower-resolution observations, and is edge-on, revealing a geometrically very thin torus (axis ratio 6.5 to 10), with a clear warp. This confirms that the classical model of a simple geometrically thick dusty torus is challenged by high resolution observations. The nuclear disks appear clumpy, and slightly lopsided. The molecular outflow in NGC~613 is now resolved out. Well inside the sphere of influence of the black holes (BH), we are now able to determine more accurately their mass, for those Seyfert spiral galaxies, in a region of the M-sigma relation where the scatter is maximum.

astro-ph.GA↗

arXiv2025

The GECKOS Survey: Resolved, multiphase observations of mass-loading and gas density in the galactic wind of NGC 4666

We present a multiphase, resolved study of the galactic wind extending from the nearby starburst galaxy NGC 4666. For this we use VLT/MUSE observations from the GECKOS program and HI data from the WALLABY survey. We identify both ionised and HI gas in a biconical structure extending to at least $z\sim$8 kpc from the galaxy disk, with increasing velocity offsets above the midplane in both phases, consistent with a multiphase wind. The measured electron density, using [SII], differs significantly from standard expectations of galactic winds. We find electron density declines from the galaxy centre to $\sim2$ kpc, then rises again, remaining high ($\sim100-300$ cm$^{-3}$) out to $\sim$5 kpc. We find that HI dominates the mass loading. The total HI mass outflow rate (above $z~>2$ kpc) is between $5-13~M_{\odot}~\rm yr^{-1}$, accounting for uncertainties from disk-blurring and group interactions. The total ionised mass outflow rate (traced by H$α$) is between $0.5~M_{\odot}~\rm yr^{-1}$ and $5~M_{\odot}~\rm yr^{-1}$, depending on $n_e(z)$ assumptions. From ALMA/ACA observations, we place an upper-limit on CO flux in the outflow which correlates to $\lesssim2.9~M_{\odot}~\rm yr^{-1}$. We also show that the entire outflow is not limited to the bicone, but a secondary starburst at the edge generates a more widespread outflow, which should be included in simulations. The cool gas in NGC 4666 wind has insufficient velocity to escape the halo of a galaxy of its mass, especially because most of the mass is present in the slower atomic phase. This strong biconical wind contributes to gas cycling around the galaxy.

astro-ph.GA↗

arXiv2025

Origin of gas in the Magellanic Bridge: MeerKAT detection of HI 21-cm absorption

HI 21-cm absorption lines are investigated to determine the origin of the neutral atomic hydrogen (HI) of the Magellanic Bridge (MB). Using the MeerKat Absorption Line Survey (MALS) data we report the detection of an HI absorption line at a peak signal-to-noise ratio of 10 caused by MB gas against the radio source J033242.97-724904.5. In combination with earlier data obtained with the Australia Telescope Compact Array (ATCA) our new detected HI line permits the exploration of the MB atomic hydrogen gas across 4-6 kpc. The radial velocity profiles from the ATCA data and new data from MALS are analysed. Apart from the excitation conditions, the radial velocity structure of the HI gas seen in emission and absorption is investigated. Eventually the gas-to-dust ratio is quantified to identify the origin of the MB gas being either from the SMC (Small Magellanic Cloud) or the LMC (Large Magellanic Cloud). The HI absorption lines towards lines of sight separated by several kpc consistently coincide with the densest and perhaps coolest gas at the lower radial-velocity limit of the corresponding HI emission profiles. The gas-to-dust ratio is found to be consistent with an origin of the MB gas from the LMC. The large scale velocity distribution as seen from the HI absorption features favors the LMC-SMC direct collision scenario over the close fly-by scenario, as also currently found by numerical simulations.

astro-ph.GA↗

arXiv2025

Scaling relations at the central regions of nearby galaxies

Scaling relations between galactic parameters represent key pieces of evidence for investigating the processes of galaxy formation and evolution. In most studies, these relations have been obtained for large portions of the galaxies (i.e., on kpc scales), but it is also important to evaluate these relations in smaller scales. In this work, we used optical data cubes of a subsample of nearby galaxies of the DIVING 3D survey. These allowed us to analyze the scaling relations involving stellar velocity dispersion, stellar population age, and stellar population metallicity at the nuclear and circumnuclear regions of galaxies. We detected correlations between the stellar velocity dispersion and the age, metallicity, and total stellar mass. These correlations are independent of galaxy inclinations, considering all morphological types, nuclear activity, and the presence or absence of galactic bars. We detected, for the first time, a correlation between the stellar velocity dispersion and stellar metallicity in the nuclear regions of galaxies. It is found to be qualitatively consistent with the well-known stellar mass-metallicity relation. We also noted that barred galaxies tend to show younger and less metal-rich stellar populations than unbarred galaxies in the central regions, which may be a consequence of the bar triggering star formation in the nuclear regions of these objects. Some active galactic nuclei (AGNs) in our sample are positioned above the observed correlation between stellar velocity dispersion and stellar population age, suggesting that their nuclear stellar populations are younger than expected. This may be a consequence of positive AGN feedback, triggering star formation. Conversely, starburst galaxies do not show nuclear stellar populations at ages over one billion years.

astro-ph.GA↗