Astrophysics of Galaxies (astro-ph.GA)

Abstract: NGC\,7793, NGC\,300, M33 and NGC\,2403 are four nearby undisturbed and bulgeless low-mass spiral galaxies with similar morphology and stellar mass. They are ideal laboratories to study disc formation scenarios and stellar mass growth histories. We construct a simple chemical evolution model by assuming that discs grow gradually with continuous metal-free gas infall and metal-enriched gas outflow. By means of the classical $\chi^{2}$ methodology, applied to the model predictions, the best combination of free parameters capable of reproducing the corresponding present-day observations is determined, i.e. the radial dependence of the infall timescale $\tau=0.1r/{R_{\rm d}}+3.4\,{\rm Gyr}$ ($R_{\rm d}$ is the disc scale-length) and the gas outflow efficiency $b_{\rm out}=0.2$. The model results are in excellent agreement with the general predictions of the inside-out growth scenario for the evolution of spiral galaxies. About 80\% of the stellar mass of NGC\,7793 is assembled within the last 8\,Gyr and 40\% within the last 4\,Gyr. By comparing the best-fitting model results of the three other galaxies we obtain similar results, 72\% (NGC\,300), 66\% (NGC\,2403) and 79\% (M33) stellar mass were assembled within the past $\sim\rm 8\,Gyr$ (i.e. $z\,=\,1$). These four disc galaxies simultaneously increase their sizes and stellar masses as time goes by and they grow in size at $\sim\,0.30$ times the rate at which they grow in mass. The scale-lengths of these four discs are now 20\% -- 25\% larger than at $z\,=\,1$. Our best-fitting model predicted the stellar mass-metallicity relation and the metallicity gradients, constrained by the observed metallicities from HII-regions emission line analysis, agree well with the observations measured from individual massive red and blue supergiant stars and population synthesis of SDSS galaxies.

Abstract: The formation of galaxy clusters is a complicated process that probably involves the accretion of galaxies in groups, as observed in nearby clusters, such as Virgo and Fornax. The members of the groups undergo "preprocessing" prior to cluster infall, which affects their stellar populations and morphology. In this paper I present an extreme example of such an accretion event selected from the IllustrisTNG100 simulation. The group, composed of three full-sized disky galaxies and a number of smaller satellites, is accreted early, with the first pericenter around the cluster at redshift z=1.3. Before the infall, the three galaxies interact strongly in pairs within the group, which produces tidally induced bars in the two more massive ones. The interactions also lead to mass exchange and trigger some star formation activity resulting in temporary rejuvenation of their stellar populations. After infall, they all undergo seven pericenter passages around the cluster, experiencing strong mass loss in the dark matter and gas components, as well as reddening of the stellar populations. Their tidally induced bars are, however, preserved and even enhanced probably due to the loss of gas via ram-pressure stripping in the intracluster medium. The study demonstrates that group accretion can happen very early in cluster formation and proposes another scenario for the formation of tidally induced bars.

Abstract: The reactions of ground state atomic carbon, C(3P), are likely to be important in astrochemistry due to the high abundance levels of these atoms in the dense interstellar medium. Here we present a study of the gas-phase reaction between C(3P) and acetone, CH3COCH3. Experimentally, rate constants were measured for this process over the 50 to 296 K range using a continuous-flow supersonic reactor, while secondary measurements of H(2S) atom formation were also performed over the 75 to 296 K range to elucidate the preferred product channels. C(3P) atoms were generated by In-situ pulsed photolysis of carbon tetrabromide, while both C(3P) and H(2S) atoms were detected by pulsed laser induced fluorescence. Theoretically, quantum chemical calculations were performed to obtain the various complexes, adducts and transition states involved in the C(3P) + CH3COCH3 reaction over the 3A'' potential energy surface, allowing us to better understand the reaction pathways and help to interpret the experimental results. The derived rate constants are large, (2-3) x 10-10 cm3 s-1 , displaying only weak temperature variations; a result that is consistent with the barrierless nature of the reaction. As this reaction is not present in current astrochemical networks, its influence on simulated interstellar acetone abundances is tested using a gas-grain dense interstellar cloud model. For interstellar modelling purposes, the use of a temperature independent value for the rate constant, k(C+CH3COCH3 )= 2.2 x 10-10 cm3 s-1, is recommended. The C(3P) + CH3COCH3 reaction decreases gas-phase CH3COCH3 abundances by as much as two orders of magnitude at early and intermediate cloud ages.

Abstract: In this paper we present the first-ever $L$- and $M$-band interferometric observations of Circinus, building upon a recent $N$-band analysis. We used these observations to reconstruct images and fit Gaussian models to the $L$ and $M$ bands. Our findings reveal a thin edge-on disk whose width is marginally resolved and is the spectral continuation of the disk imaged in the $N$ band to shorter wavelengths. Additionally, we find a point-like source in the $L$ and $M$ bands that, based on the $LMN$-band spectral energy distribution fit, corresponds to the $N$-band point source. We also demonstrate that there is no trace of direct sightlines to hot dust surfaces in the circumnuclear dust structure of Circinus. By assuming the dust is present, we find that obscuration of A$_{\rm V} \gtrsim 250$ mag is necessary to reproduce the measured fluxes. Hence, the imaged disk could play the role of the obscuring "torus" in the unified scheme of active galactic nuclei. Furthermore, we explored the parameter space of the disk + hyperbolic cone radiative transfer models and identify a simple modification at the base of the cone. Adding a cluster of clumps just above the disk and inside the base of the hyperbolic cone provides a much better match to the observed temperature distribution in the central aperture. This aligns well with the radiation-driven fountain models that have recently emerged. Only the unique combination of sensitivity and spatial resolution of the VLTI allows such models to be scrutinized and constrained in detail. We plan to test the applicability of this detailed dust structure to other MATISSE-observed active galactic nuclei in the future.

Abstract: Gravitational microlensing is a powerful method for discovering Isolated Stellar-Mass Black Holes(ISMBHs). These objects make long-duration microlensing events. To characterize these lensing objects by fully resolving the microlensing degeneracy, measurements of parallax and astrometric deflections are necessary. Microlensing events due to ISMBHs have considerable astrometric deflections, but small parallax amplitudes as $\pi_{\rm E} \propto 1/\sqrt{M_{\rm l}}$, where $M_{\rm l}$ is the lens mass. We numerically investigate the possibility of inferring parallax amplitude from astrometric deflection in microlensing events due to ISMBHs. The parallax amplitude in astrometric deflections is proportional to the relative parallax $\pi_{\rm{rel}}$, which means (i) does not strongly depend on $M_{\rm l}$, and (ii) increases in microlensing observations toward the Magellanic Clouds(MCs). We assume these events are potentially detected in upcoming microlensing surveys-(1): the \wfirst\ observations of the Galactic bulge (GB), and (2): the LSST observations of the Large MC(LMC)-, and the Extremely Large Telescope (ELT) follows up them with one data point every ten days. We evaluate the probability of inferring parallax amplitude from these observations by calculating the Fisher/Covariance matrices. For GB, the efficiencies for discerning parallax amplitudes with a relative error $<4\%$ through astrometric, and photometric observations are $3.8\%$, and $29.1\%$, respectively. For observations toward the LMC, these efficiencies are $41.1\%$, and $23.0\%$, respectively. Measuring parallax amplitude through astrometric deflections is plausible in the GB events with the lens distance $\lesssim 2.7$kpc, and in the LMC halo-lensing. The ELT telescope by monitoring long-duration microlensing events can detect astrometric deflections, and their parallax-induced deviations.

Abstract: We present the survey design and initial results of the ALMA Cycle~9 program of DUALZ, which aims to establish a joint ALMA and JWST public legacy field targeting the massive galaxy cluster Abell 2744. DUALZ features a contiguous $4'\times6'$ ALMA 30-GHz-wide mosaic in Band 6, covering areas of $\mu>2$ down to a sensitivity of $\sigma=32.7$~$\mu$Jy. Through a blind search, we identified 69 dust continuum sources at S/N $\gtrsim5.0$ with median redshift and intrinsic 1.2-mm flux of $z=2.30$ and $S_{\rm 1.2mm}^{\rm int}=0.24$~mJy. Of these, 27 have been spectroscopically confirmed, leveraged by the latest NIRSpec observations, while photometric redshift estimates are constrained by the comprehensive \hst, NIRCam, and ALMA data for the remaining sources. With priors, we further identify a \cii158~$\mu$m line emitter at $z=6.3254\pm0.0004$, confirmed by the latest NIRSpec spectroscopy. The NIRCam counterparts of the 1.2-mm continuum exhibit undisturbed morphologies, denoted either by disk or spheroid, implying the triggers for the faint mm emission are less catastrophic than mergers. We have identified 8 \hst-dark galaxies (F150W$>$27~mag, F150W$-$F444W$>$2.3) and 2 JWST-dark (F444W$>$30~mag) galaxy candidates among the ALMA continuum sources. The former includes face-on disk galaxies, hinting that substantial dust obscuration does not always result from inclination. We also detect a marginal dust emission from an X-ray-detected galaxy at $z_{\rm spec}=10.07$, suggesting an active co-evolution of the central black hole and its host. We assess the infrared luminosity function up to $z\sim10$ and find it consistent with predictions from galaxy formation models. To foster diverse scientific outcomes from the community, we publicly release reduced ALMA mosaic maps, cubes, and the source catalog (URL: https://jwst-uncover.github.io/DR2.html\#DUALZ).

Abstract: The circum-galactic medium (CGM) can feasibly be mapped by multiwavelength surveys covering broad swaths of the sky. With multiple large datasets becoming available in the near future, we develop a likelihood-free Deep Learning technique using convolutional neural networks (CNNs) to infer broad-scale physical properties of a galaxy's CGM and its halo mass for the first time. Using CAMELS (Cosmology and Astrophysics with MachinE Learning Simulations) data, including IllustrisTNG, SIMBA, and Astrid models, we train CNNs on Soft X-ray and 21-cm (HI) radio 2D maps to trace hot and cool gas, respectively, around galaxies, groups, and clusters. Our CNNs offer the unique ability to train and test on ''multifield'' datasets comprised of both HI and X-ray maps, providing complementary information about physical CGM properties and improved inferences. Applying eRASS:4 survey limits shows that X-ray is not powerful enough to infer individual halos with masses $\log(M_{\rm{halo}}/M_{\odot}) < 12.5$. The multifield improves the inference for all halo masses. Generally, the CNN trained and tested on Astrid (SIMBA) can most (least) accurately infer CGM properties. Cross-simulation analysis -- training on one galaxy formation model and testing on another -- highlights the challenges of developing CNNs trained on a single model to marginalize over astrophysical uncertainties and perform robust inferences on real data. The next crucial step in improving the resulting inferences on physical CGM properties hinges on our ability to interpret these deep-learning models.

Abstract: The mass-metallicity relation (MZR) represents one of the most important scaling relations in the context of galaxy evolution, comprising a positive correlation between stellar mass and metallicity (Z). The fundamental metallicity relation (FMR) introduces a new parameter, the star formation rate (SFR), in the dependence. While several studies found that Z is anti-correlated with the SFR at fixed mass, the validity of this statement has been questioned extensively and no widely-accepted consensus has been reached yet. With this work, we investigate the FMR in nine nearby, spatially-resolved, dwarf galaxies, using gas diagnostics on integral-field spectroscopic data of the Multi Unit Spectroscopic Explorer (MUSE), pushing such investigations to lower galaxy masses and higher resolutions. We find that both the MZR and FMR exhibit different behaviours within different star forming regions of the galaxies. We find that the SFR surface density - metallicity anti-correlation is tighter in the low-mass galaxies of our sample. For all the galaxies considered, we find a SFR surface density - stellar mass surface density correlation. We propose that the main reason behind these findings is connected to the accretion mechanisms of the gas fuelling star formation -- low-mass, metal-poor galaxies accrete pristine gas from the intergalactic medium, while in more massive and metal-enriched systems the gas responsible for star formation is recycled from previous star forming episodes.