Search

Understanding faint dwarf galaxies is fundamental to the development of a robust theory of galaxy formation on small scales. Since the discovery of a population of ultra diffuse galaxies (UDGs) rich in globular clusters (GCs) in Coma, an increasing number of studies on low surface brightness dwarf galaxies (LSBds) have been published in recent years. The most massive LSBds have been observed predominantly in groups and clusters, with properties displaying dependence on the environment. In this work, we use deep DECam imaging to systematically identify LSBds and their GC populations around the low-density environment of NGC 3115. We carefully analyse the structure and morphology of 24 candidates, 18 of which are reported for the first time. Most candidates exhibit red colours suggesting a connection between their colour and distance to NGC 3115. We followed up with Gemini GMOS imaging 9 LSBds to properly identify their GC populations. We derive lower limits for the number of GCs associated with each galaxy. Our analysis reveals that they occur around of the same loci of Fornax LSB dwarf GC systems. The relationship between the number of GCs and total mass provides a tool in which, by counting the GCs in these galaxies, we estimate an upper limit for the total mass of these LSB dwarfs, obtaining the mean value of |$\sim 3.3\times 10^{10}$|  M |$_{\odot }$|⁠. Our results align with expectations for dwarf-sized galaxies, particularly regarding the distribution and specific frequency of their GC systems. [ABSTRACT FROM AUTHOR]

We study 51 jellyfish galaxy candidates in the Fornax, Antlia, and Hydra clusters. These candidates are identified using the JClass scheme based on the visual classification of wide-field, twelve-band optical images obtained from the Southern Photometric Local Universe Survey. A comprehensive astrophysical analysis of the jellyfish (JClass > 0), non-jellyfish (JClass = 0), and independently organized control samples is undertaken. We develop a semi-automated pipeline using self-supervised learning and similarity search to detect jellyfish galaxies. The proposed framework is designed to assist visual classifiers by providing more reliable JClasses for galaxies. We find that jellyfish candidates exhibit a lower Gini coefficient, higher entropy, and a lower 2D Sérsic index as the jellyfish features in these galaxies become more pronounced. Jellyfish candidates show elevated star formation rates (including contributions from the main body and tails) by |$\sim$| 1.75 dex, suggesting a significant increase in the SFR caused by the ram-pressure stripping phenomenon. Galaxies in the Antlia and Fornax clusters preferentially fall towards the cluster's centre, whereas only a mild preference is observed for Hydra galaxies. Our self-supervised pipeline, applied in visually challenging cases, offers two main advantages: it reduces human visual biases and scales effectively for large data sets. This versatile framework promises substantial enhancements in morphology studies for future galaxy image surveys. [ABSTRACT FROM AUTHOR]

Relic galaxies are massive, compact, and quiescent objects observed in the local Universe that have not experienced any significant interaction episodes or merger events since about z  = 2, remaining relatively unaltered since their formation. On the other hand, massive and compact early-type galaxies (cETGs) in the local Universe appear to show similar properties to Relic galaxies, despite having substantial accretion history. Relic galaxies, with frozen history, can provide important clues about the intrinsic processes related to the evolutionary pathways of ETGs and the role that mergers play in their evolution. Using the high-resolution cosmological simulation TNG50-1 from IllustrisTNG project, we investigate the assembly history of a sample of massive, compact, old, and quiescent subhaloes split by satellite accretion fraction. We compare the evolutionary pathways at three cosmic epochs: z  = 2, z  = 1.5, and z  = 0, using the orbital decomposition numerical method to investigate the stellar dynamics of each galactic kinematical component and their environmental correlations. Our results point to a steady pathway across time that is not strongly dependent on the mergers or the environment. Relics and cETGs do not show a clear preference for high- or low-density environments within the volume explored at z  = 0, as they are found in both scenarios. However, the progenitors of Relic galaxies have consistently resided in high-density environments since z  = 2, while cETGs were shifted to such environments at a later stage. The merger history can be recovered from the stellar kinematics imprints in the local Universe. Relics and cETGs show consistently dynamical similarities at z  = 2 and differences at z  = 0 to disc, bulge, and hot inner stellar halo. In the current scenario, the mergers that drive the growth of cETGs do not give rise to a new and distinct evolutionary pathway when compared to Relics. [ABSTRACT FROM AUTHOR]

We present a spatially resolved stellar population analysis of 61 jellyfish galaxies and 47 control galaxies observed with ESO/MUSE attempting to understand the general trends of the stellar populations as a function of the stripping intensity and mass. This is the public sample from the GASP programme, with 0.01 < z < 0.15 and 8.9 < log (M ⋆/M⊙) < 12.0. We apply the spectral population synthesis code fado to fit self-consistently both the stellar and nebular contributions to the spectra of the sources. We present 2D morphological maps for mean stellar ages, metallicities, gas-phase oxygen abundances, and star formation rates for the galaxies with Integrated Nested Laplace Approximation (inla), which is efficient in reconstructing spatial data of extended sources. We find that 'extreme stripping' and 'stripping' galaxies are typically younger than the other types. Regarding stellar and nebular metallicities, the 'stripping' and 'control passive' galaxies are the most metal-poor. Based on the phase space for jellyfish cluster members we find trends in ages, metallicities, and abundances with different regions of the diagram. We also compute radial profiles for the same quantities. We find that both the stripping and the stellar masses seem to influence the profiles, and we see differences between various groups and distinct mass bins. The radial profiles for different mass bins present relations already shown in the literature for undisturbed galaxies, i.e. profiles of ages and metallicities tend to increase with mass. However, beyond ∼0.75 effective radius, the ages of the most massive galaxies become similar to or lower than the ages of the lower mass ones. [ABSTRACT FROM AUTHOR]

Globular clusters (GCs) are proxies of the formation assemblies of their host galaxies. However, few studies exist targeting GC systems of spiral galaxies up to several effective radii. Through 12-band Javalambre Photometric Local Universe Survey (J-PLUS) imaging, we study the point sources around the M 81/M 82/NGC 3077 triplet in search of new GC candidates. We develop a tailored classification scheme to search for GC candidates based on their similarity to known GCs via a principal component analysis projection. Our method accounts for missing data and photometric errors. We report 642 new GC candidates in a region of 3.5 deg2 around the triplet, ranked according to their Gaia astrometric proper motions when available. We find tantalizing evidence for an overdensity of GC candidate sources forming a bridge connecting M 81 and M 82. Finally, the spatial distribution of the GC candidates (g − i) colours is consistent with halo/intra-cluster GCs, i.e. it gets bluer as they get further from the closest galaxy in the field. We further employ a regression-tree-based model to estimate the metallicity distribution of the GC candidates based on their J-PLUS bands. The metallicity distribution of the sample candidates is broad and displays a bump towards the metal-rich end. Our list increases the population of GC candidates around the triplet by threefold, stresses the usefulness of multiband surveys in finding these objects, and provides a testbed for further studies analysing their spatial distribution around nearby (spirals) galaxies. [ABSTRACT FROM AUTHOR]

Relic galaxies are massive compact quiescent galaxies that formed at high-redshift and remained almost unchanged since then. In this work, we search for analogues to relic galaxies in the TNG50 cosmological simulations to understand relic formation and test the ability of TNG50 to reproduce such rare objects. Using stellar mass, age, radius, quiescence, and stellar assembly criteria, we find five subhaloes in TNG50 that could be potential relic analogues. We compare their properties with other constraints imposed by a sample of 13 observed relic galaxies. We find one analogue in TNG50 that simultaneously satisfies most of the available observational constraints, such as metallicity and morphology. It also shows similarities to the confirmed relic NGC 1277, regarding environment and dark matter fraction. By taking into account a degree of relicness, a second relic analogue may also be considered. However, the central parts of the brightness and density profiles of the analogues are less steep than that of real relic galaxies, possibly due to limited numerical resolution. We identify two formation pathways of relic analogues in TNG50 depending on their environment: they either have their remaining gas stripped during the infall into a cluster at z ≲ 1.2 or consume it before z > 1.5. They are then deprived of significant star formation, leaving their stellar populations almost unaltered during the last 9 Gyr. We also find that the analogue progenitors at z ∼ 4 inhabit more massive haloes than progenitors of quiescent galaxies with similar stellar mass at z ∼ 0. [ABSTRACT FROM AUTHOR]

We analyse the globular cluster (GC) systems of a sample of 15 massive, compact early-type galaxies (ETGs), 13 of which have already been identified as good relic galaxy candidates on the basis of their compact morphologies, old stellar populations and stellar kinematics. These relic galaxy candidates are likely the nearby counterparts of high-redshift red nugget galaxies. Using F814W (≈ I) and F160W (≈ H) data from the WFC3 camara onboard the Hubble Space Telescope , we determine the total number, luminosity function, specific frequency, colour, and spatial distribution of the GC systems (GCSs). We find lower specific frequencies (SN < 2.5 with a median of SN = 1) than ETGs of comparable mass. This is consistent with a scenario of rapid, early dissipative formation, with relatively low levels of accretion of low-mass, high- SN satellites. The GC half-number radii are compact, but follow the relations found in normal ETGs. We identify an anticorrelation between the specific angular momentum (λ R) of the host galaxy and the (I − H) colour distribution width of their GCSs. Assuming that λ R provides a measure of the degree of dissipation in massive ETGs, we suggest that the (I − H) colour distribution width can be used as a proxy for the degree of complexity of the accretion histories in these systems. [ABSTRACT FROM AUTHOR]

We explore the morphometric properties of a group of 73 ram-pressure stripping candidates in the A901/A902 multicluster system, at z ∼ 0.165, to characterize the morphologies and structural evolution of jellyfish galaxies. By employing a quantitative measurement of morphometric indicators with the algorithm morfometryka on Hubble Space Telescope (F 606 W) images of the galaxies, we present a novel morphology-based method for determining trail vectors. We study the surface brightness profiles and curvature of the candidates and compare the results obtained with two analysis packages, morfometryka and iraf/ellipse on retrieving information of the irregular structures present in the galaxies. Our morphometric analysis shows that the ram-pressure stripping candidates have peculiar concave regions in their surface brightness profiles. Therefore, these profiles are less concentrated (lower Sérsic indices) than other star-forming galaxies that do not show morphological features of ram-pressure stripping. In combination with morphometric trail vectors, this feature could both help identify galaxies undergoing ram-pressure stripping and reveal spatial variations in the star formation rate. [ABSTRACT FROM AUTHOR]

This work employs high-quality Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) F606W and F814W photometry to correct for the differential reddening affecting the colour–magnitude diagram (CMD) of the poorly studied globular cluster (GC) Palomar 2. Differential reddening is taken into account by assuming that morphological differences among CMDs extracted across the field of view of Palomar 2 correspond essentially to shifts (quantified in terms of δ E (B − V)) along the reddening vector due to a non-uniform dust distribution. The average reddening difference over all partial CMDs is |$\overline{{\delta E(B-V)}}=0.24\pm 0.08$|⁠ , with the highest reaching δ E (B − V) = 0.52. The corrected CMD displays well-defined and relatively narrow evolutionary sequences, especially for the evolved stars, i.e. the red giant, horizontal, and asymptotic giant branches (RGB, HB, and AGB, respectively). The average width of the upper main sequence and RGB profiles of the corrected CMD corresponds to 56 per cent of the original one. Parameters measured on this CMD show that Palomar 2 is ≈13.25 Gyr old, has the mass |$M\sim 1.4\times 10^5\, \rm {\mathrm{ M}_\odot}$| stored in stars, is affected by the foreground E (B − V) ≈ 0.93, is located at d⊙ ≈ 26 kpc from the Sun, and is characterized by the global metallicity Z /Z⊙ ≈ 0.03, which corresponds to the range −1.9 ≤ [Fe/H] ≤ −1.6 (for 0.0 ≤ [α/Fe] ≤ +0.4), quite consistent with other outer halo GCs. Additional parameters are the absolute magnitude MV  ≈ −7.8, and the core and half-light radii r C ≈ 2.6 pc and R HL ≈ 4.7 pc, respectively. [ABSTRACT FROM AUTHOR]

We present the results of a systematic search and characterization of galaxies with morphological signatures of ram pressure stripping, known as jellyfish galaxies, in the multicluster system A901/2, at z ∼ 0.165, as part of the OMEGA survey. By visually inspecting Advanced Camera for Surveys/ Hubble Space Telescope F606W images looking for morphological signatures of ram pressure stripping events in H α-emitting galaxies, we identify a total of 70 jellyfish candidates. Of these, 53 are clearly star-forming galaxies and five are highly probable active galactic nucleus (AGN) hosts, the classification of the remaining galaxies is more uncertain. They have late-type and irregular morphologies, and most of them are part of the blue cloud with only. four being previously classified as dusty reds. The AGN activity is not prominent in the sample and, of the few cases of galaxies hosting AGN, such activity does not seem to be correlated to the gas-stripping phenomenon. Our jellyfish galaxy candidates do not have a preferential pattern of motion within the multicluster system, although the most compelling cases appear to inhabit the inner regions of the most massive sub-cluster centres. The specific star formation rate of these galaxies indicates that their star formation activity is enhanced, in contrast with what is observed for the rest of the star-forming galaxy population in the system. Half of the sample is forming stars at a higher rate than the main sequence for field galaxies, and this behaviour is more evident for the most compelling candidates. For some galaxies, the spatially resolved H α emission appears to be as disturbed and extended as their continuum counterparts. Our findings point towards a scenario where the ram pressure stripping is triggering a period of intense and extended star formation throughout the galaxy while it is also disturbing the morphology. This is the largest sample of jellyfish galaxy candidates found in a single system suggesting that cluster mergers might be the ideal environment for studying ram pressure stripping effects. [ABSTRACT FROM AUTHOR]

Globular clusters (GCs) can be considered discrete, long-lived, dynamical tracers that retain crucial information about the assembly history of their parent galaxy. In this paper, we present a new catalogue of GC velocities and colours for the lenticular galaxy NGC 1023, we study their kinematics and spatial distribution, in comparison with the underlying stellar kinematics and surface brightness profile, and we test a new method for studying GC properties. Specifically, we decompose the galaxy light into its spheroid (assumed to represent the bulge+halo components) and disc components and use it to assign to each GC a probability of belonging to one of the two components. Then we model the galaxy kinematics, assuming a disc and spheroidal component, using planetary nebulae and integrated stellar light. We use this kinematic model and the probability previously obtained from the photometry to recalculate for each GC its likelihood of being associated with the disc, the spheroid, or neither. We find that the reddest GCs are likely to be associated with the disc, as found for faint fuzzies in this same galaxy, suggesting that the disc of this S0 galaxy originated at z ∍ 2. The majority of blue GCs are found likely to be associated with the spheroidal (hot) component. The method also allows us to identify objects that are unlikely to be in equilibrium with the system. In NGC 1023 some of the rejected GCs form a substructure in phase space that is connected with NGC 1023 companion galaxy. [ABSTRACT FROM AUTHOR]

General Relativity (GR) has been successfully tested mainly at Solar system scales; however, galaxy-scale tests have become popular in the last few decades. In this work, we investigate the ηPPN parameter, which is commonly defined by the ratio of two scalar potentials that appears in the cosmological linearly perturbed metric. Under the assumption of GR and a vanish anisotropic stress tensor, ηPPN = 1. Using ALMA, HST , and VLT/MUSE data, we combine mass measurements, using gravitational lensing and galactic dynamics, for the SDP.81 lens galaxy (z = 0.299) to constrain ηPPN. By using a flexible and self-consistent mass profile, our fiducial model takes into account the contribution of the stellar mass and a dark matter halo to reconstruct the lensed galaxy and the spatially resolved stellar kinematics. We infer, after accounting for systematic uncertainties related to the mass model, cosmology, and kinematics, |$\eta _{\text{PPN}} = 1.13^{+0.03}_{-0.03}\pm 0.20\, (\text{sys})$|⁠ , which is in accordance with GR predictions. Better spectroscopy data are needed to push the systematics down and bring the uncertainty to the percentage level since our analysis shows that the main source of the systematics is related to kinematics, which heavily depends on the signal-to-noise ratio of the spectra. [ABSTRACT FROM AUTHOR]

Multiple stellar populations (MSPs) are a ubiquitous phenomenon in Galactic globular clusters (GCs). By probing different spectral ranges affected by different absorption lines using the multiband photometric survey S-PLUS, we study four GCs – NGC 104, NGC 288, NGC 3201, and NGC 7089 – that span a wide range of metallicities. With the combination of broad and narrow-band photometry in 12 different filters from 3485A (u) to 9114A (z), we identified MSPs along the rectified red-giant branch in colour–magnitude diagrams and separated them using a K-means clustering algorithm. Additionally, we take advantage of the large Field of View of the S-PLUS detector to investigate radial trends in our sample. We report on six colour combinations that can be used to successfully identify two stellar populations in all studied clusters and show that they can be characterized as Na-rich and Na-poor. For both NGC 288 and NGC 7089, their radial profiles show a clear concentration of 2P population. This directly supports the formation theories that propose an enrichment of the intra-cluster medium and subsequent star formation in the more dense central regions. However, in the case of NGC 3201, the trend is reversed. The 1P is more centrally concentrated, in direct contradiction with previous literature studies. NGC 104 shows a well-mixed population. We also constructed radial profiles up to 1 half-light radius of the clusters with HST data to highlight that radial differences are lost in the inner regions of the GCs and that wide-field studies are essential when studying this. [ABSTRACT FROM AUTHOR]

Most of the observed galaxies cannot be resolved into individual stars and are studied through their integrated spectrum using simple stellar populations (SSPs) models, with stellar libraries being a key ingredient in building them. Spectroscopic observations are increasingly being directed towards the near-infrared (NIR), where much is yet to be explored. SSPs in the NIR are still limited, and there are inconsistencies between different sets of models. One of the ways to minimize this problem is to have reliable NIR stellar libraries. The main goal of this work is to present smarty (mileS Moderate resolution neAr-infRared sTellar librarY) a ∼0.9−2.4 |$\mu$| m stellar spectral library composed of 31 stars observed with the Gemini Near-IR Spectrograph (GNIRS) at the 8.1 m Gemini North telescope and make it available to the community. The stars were chosen from the miles library, for which the atmospheric parameters are reliable (and well-tested), to populate different regions of the Hertzsprung–Russell (HR) diagram. Furthermore, five of these stars have NIR spectra available that we use to assess the quality of smarty. The remaining 26 stars are presented for the first time in the NIR. We compared the observed smarty spectra with synthetic and interpolated spectra, finding a mean difference of |$\sim 20~{{\ \rm per\ cent}}$| in the equivalent widths and ∼1 per cent in the overall continuum shape in both sets of comparisons. We computed the spectrophotometric broad-band magnitudes and colours and compared them with the 2MASS ones, resulting in mean differences up to 0.07 and 0.10 mag in magnitudes and colours, respectively. In general, a small difference was noted between the smarty spectra corrected using the continuum from the interpolated and the theoretical stars. [ABSTRACT FROM AUTHOR]

In this work, we characterize the properties of the object SDSS J020536.84−081424.7, an extended nebular region with projected extension of 14 × 14 kpc2 in the line of sight of the ETG Mrk 1172, using unprecedented spectroscopic data from MUSE. We perform a spatially resolved stellar population synthesis and estimate the stellar mass for both Mrk 1172 (1 × 1011 M⊙) and our object of study (3 × 109 M⊙). While the stellar content of Mrk 1172 is dominated by an old (∼10 Gyr) stellar population, the extended nebular emission has its light dominated by young to intermediate age populations (from ∼100 Myr to ∼1 Gyr) and presents strong emission lines such as H β; [O  iii ] λλ4959, 5007 Å; H α; [N  ii ] λλ6549, 6585 Å; and [S  ii ] λλ6717, 6732 Å. Using these emission lines, we find that it is metal poor (with Z ∼ 1/3 Z⊙, comparable to the LMC) and is actively forming stars (0.70 M⊙ yr−1), especially in a few bright clumpy knots that are readily visible in H α. The object has an ionized gas mass ≥3.8 × 105 M⊙. Moreover, the motion of the gas is well described by a gas in circular orbit in the plane of a disc and is being affected by interaction wtih Mrk 1172. We conclude that SDSS J020536.84−081424.7 is most likely a dwarf irregular galaxy (the dIGal). [ABSTRACT FROM AUTHOR]

Nuclear star clusters (NSCs) are dense star clusters located at the centre of galaxies spanning a wide range of masses and morphologies. Analysing NSC occupation statistics in different environments provides an invaluable window into investigating early conditions of high-density star formation and mass assembly in clusters and group galaxies. We use HST/ACS deep imaging to obtain a catalogue of dwarf galaxies in two galaxy clusters in the Shapley supercluster: the central cluster Abell 3558 and the northern Abell 1736a. The Shapley region is an ideal laboratory to study nucleation as it stands as the highest mass concentration in the nearby Universe. We investigate the NSC occurrence in quiescent dwarf galaxies as faint as MI  = −10 mag and compare it with all other environments where nucleation data is available. We use galaxy cluster/group halo mass as a proxy for the environment and employ a Bayesian logistic regression framework to model the nucleation fraction (fn) as a function of galaxy luminosity and environment. We find a notably high fn in Abell 3558: at MI ≈ −13.1 mag, half the galaxies in the cluster host NSCs. This is higher than in the Virgo and Fornax clusters but comparable to the Coma Cluster. On the other hand, the fn in Abell 1736a is relatively lower, comparable to groups in the local volume. We find that the probability of nucleation varies with galaxy luminosity remarkably similarly in galaxy clusters. These results reinforce previous findings of the important role of the environment in NSC formation/growth. [ABSTRACT FROM AUTHOR]

Recovering the origins of lenticular galaxies can shed light on the understanding of galaxy and compare them with the kinematics of planetary nebulae (PNe). The PNe and GC data come from the Planetary Nebulae Spectrograph and the SLUGGS Surveys. Through photometric spheroid-disc decomposition and PNe kinematics. we find the probability for a given GC to belong to either the spheroid or the disc of its host galaxy or be rejected from the model. We find that there is no correlation between the components that the GCs are likely to belong to and their colours. Particularly, for NGC 2768, we find that its red GCs display rotation preferentially at inner radii (Re < 1). In the case of the GC system of NGC 3115, we find a group of GCs with similar kinematics that are not likely to belong to either its spheroid or disc. For NGC 7457, we find that 70 per cent of its GCs are likely to belong to the disc. Overall, our results suggest that these galaxies assembled into S0s through different evolutionary paths. Mergers seem to have been very important for NGC 2768 and NGC 3115 while NGC 7457 is more likely to have experienced secular evolution. [ABSTRACT FROM AUTHOR]

The Vera C. Rubin Observatory will undertake the Legacy Survey of Space and Time, providing an unprecedented, volume-limited catalog of star clusters in the Southern Sky, including Galactic and extragalactic star clusters. The Star Clusters subgroup of the Stars, Milky Way and Local Volume Working Group has identified key areas where Rubin Observatory will enable significant progress in star cluster research. This roadmap represents our science cases and preparation for studies of all kinds of star clusters from the Milky Way out to distances of tens of megaparsecs. [ABSTRACT FROM AUTHOR]

In this series of papers, we employ several machine learning (ML) methods to classify the point-like sources from the miniJPAS catalogue, and identify quasar candidates. Since no representative sample of spectroscopically confirmed sources exists at present to train these ML algorithms, we rely on mock catalogues. In this first paper, we develop a pipeline to compute synthetic photometry of quasars, galaxies, and stars using spectra of objects targeted as quasars in the Sloan Digital Sky Survey. To match the same depths and signal-to-noise ratio distributions in all bands expected for miniJPAS point sources in the range 17.5 ≤ r < 24, we augment our sample of available spectra by shifting the original r -band magnitude distributions towards the faint end, ensure that the relative incidence rates of the different objects are distributed according to their respective luminosity functions, and perform a thorough modelling of the noise distribution in each filter, by sampling the flux variance either from Gaussian realizations with given widths, or from combinations of Gaussian functions. Finally, we also add in the mocks the patterns of non-detections which are present in all real observations. Although the mock catalogues presented in this work are a first step towards simulated data sets that match the properties of the miniJPAS observations, these mocks can be adapted to serve the purposes of other photometric surveys. [ABSTRACT FROM AUTHOR]

NGC 4382 is a merger-remnant galaxy that has been classified as morphological type E2, S0, and even Sa. In this work, we performed a photometric and spectroscopic analysis of the globular cluster (GC) system of this peculiar galaxy in order to provide additional information about its history. We used a combination of photometric data in different filters, and multiobject and long-slit spectroscopic data obtained using the Gemini/GMOS instrument. The photometric analysis of the GC system, using the Gaussian Mixture Model algorithm in the colour plane, reveals a complex colour distribution within R gal < 5 arcmin (26.1 kpc), showing four different groups: the typical blue and red subpopulations, a group with intermediate colours, and the fourth group towards even redder colours. From the spectroscopic analysis of 47 GCs, confirmed members of NGC 4382 based on radial velocities, we verified 3 of the 4 photometric groups from the analysis of their stellar populations using the ULySS code. NGC 4382 presents the classic blue (10.4 ± 2.8 Gyr, [Fe/H] = −1.48 ± 0.18 dex), and red (12.1 ± 2.3 Gyr, [Fe/H] = −0.64 ± 0.26 dex) GCs formed earlier in the lifetime of the galaxy, and a third group of young GCs (2.2 ± 0.9 Gyr; [Fe/H] = −0.05 ± 0.28 dex). Finally, analysis of long-slit data of the galaxy reveals a luminosity-weighted mean age for the stellar population of ∼2.7 Gyr, and an increasing metallicity from [Fe/H] = −0.1 to +0.2 dex in R gal < 10 arcsec (0.87 kpc). These values, and other morphological signatures in the galaxy, are in good agreement with the younger group of GCs, indicating a common origin as a result of a recent merger. [ABSTRACT FROM AUTHOR]

In this paper, we describe a new method to select globular cluster (GC) candidates, including galaxy subtraction with unsharp masking, template fitting techniques, and the inclusion of Gaia's proper motions. We report the use of the 12-band photometric system used by S-PLUS to determine radial velocities and stellar populations of GCs around nearby galaxies. Specifically, we assess the effectiveness of identifying GCs around nearby and massive galaxies (D < 20 Mpc and σ > 200 km s-1) in a multiband survey such as S-PLUS by using spectroscopically confirmed GCs and literature GC candidate lists around the bright central galaxy in the Fornax cluster, NGC 1399 (D = 19 Mpc), and the isolated lenticular galaxy NGC 3115 (D  = 9.4 Mpc). Despite the shallow survey depth, which limits this work to r < 21.3 mag, we measure reliable photometry and perform robust SED fitting for a sample of 115 GCs around NGC 1399 and 42 GCs around NGC 3115, recovering radial velocities, ages, and metallicities for the GC populations. [ABSTRACT FROM AUTHOR]

The nearby Hydra cluster (∼50 Mpc) is an ideal laboratory to understand, in detail, the influence of the environment on the morphology and quenching of galaxies in dense environments. We study the Hydra cluster galaxies in the inner regions (1 R 200) of the cluster using data from the Southern Photometric Local Universe Survey, which uses 12 narrow and broad-band filters in the visible region of the spectrum. We analyse structural (Sérsic index, effective radius) and physical (colours, stellar masses, and star formation rates) properties. Based on this analysis, we find that ∼88 per cent of the Hydra cluster galaxies are quenched. Using the Dressler–Schectman test approach, we also find that the cluster shows possible substructures. Our analysis of the phase-space diagram together with densit y- based spatial clustering algorithm indicates that Hydra shows an additional substructure that appears to be in front of the cluster centre, which is still falling into it. Our results, thus, suggest that the Hydra cluster might not be relaxed. We analyse the median Sérsic index as a function of wavelength and find that for red [(u − r) ≥2.3] and earl y- type galaxies it displays a slight increase towards redder filters (13 and 18 per cent, for red and early type, respectively), whereas for blue + green [(u − r)<2.3] galaxies it remains constant. Late-type galaxies show a small decrease of the median Sérsic index towards redder filters. Also, the Sérsic index of galaxies, and thus their structural properties, do not significantly vary as a function of clustercentric distance and density within the cluster; and this is the case regardless of the filter. [ABSTRACT FROM AUTHOR]

Despite numerous efforts, it is still unclear whether lenticular galaxies (S0s) evolve from spirals whose star formation was suppressed, or formed trough mergers or disc instabilities. In this paper we present a pilot study of 21 S0 galaxies in extreme environments (field and cluster), and compare their spatially resolved kinematics and global stellar populations. Our aim is to identify whether there are different mechanisms that form S0s in different environments. Our results show that the kinematics of S0 galaxies in field and cluster are, indeed, different. Lenticulars in the cluster are more rotationally supported, suggesting that they are formed through processes that involve the rapid consumption or removal of gas (e.g. starvation, ram pressure stripping). In contrast, S0s in the field are more pressure supported, suggesting that minor mergers served mostly to shape their kinematic properties. These results are independent of total mass, luminosity, or disc-to-bulge ratio. On the other hand, the mass-weighted age, metallicity, and star formation time-scale of the galaxies correlate more with mass than with environment, in agreement with known relations from previous work, such as the one between mass and metallicity. Overall, our results re-enforce the idea that there are multiple mechanisms that produce S0s, and that both mass and environment play key roles. A larger sample is highly desirable to confirm or refute the results and the interpretation of this pilot study. [ABSTRACT FROM AUTHOR]

We analyse a set of optical-to-near-infrared long-slit nuclear spectra of 16 infrared-luminous spiral galaxies. All of the studied sources present H2 emission, which reflects the star-forming nature of our sample, and they clearly display H  i emission lines in the optical. Their continua contain many strong stellar absorption lines, with the most common features due to |$\rm{Ca\,{\small I}}$|⁠ , |$\rm{Ca\,{\small II}}$|⁠ , |$\rm{Fe\,{\small I}}$|⁠ , |$\rm{Na\,{\small I}}$|⁠ , |$\rm{Mg\,{\small I}}$|⁠ , in addition to prominent absorption bands of TiO, VO, ZrO, CN, and CO. We report a homogeneous set of equivalent width (EW) measurements for 45 indices, from optical to NIR species for the 16 star-forming galaxies as well as for 19 early-type galaxies where we collected the data from the literature. This selected set of emission and absorption-feature measurements can be used to test predictions of the forthcoming generations of stellar population models. We find correlations among the different absorption features and propose here correlations between optical and NIR indices, as well as among different NIR indices, and compare them with model predictions. Although for the optical absorption features the models consistently agree with the observations, the NIR indices are much harder to interpret. For early-type spirals the measurements agree roughly with the models, while for star-forming objects they fail to predict the strengths of these indices. [ABSTRACT FROM AUTHOR]

The A901/2 system is a rare case of galaxy cluster interaction, in which two galaxy clusters and two smaller groups are seen in route of collision with each other simultaneously. Within each of the four substructures, several galaxies with features indicative of jellyfish morphologies have been observed. In this paper, we propose a hydrodynamic model for the merger as a whole, compatible with its diffuse X-ray emission, and correlate the gas properties in this model with the locations of the jellyfish galaxy candidates in the real system. We find that jellyfish galaxies seem to be preferentially located near a boundary inside each subcluster where diffuse gas moving along with the subcluster and diffuse gas from the remainder of the system meet. The velocity change in those boundaries is such that a factor of up to ∼1000 increase in the ram pressure takes place within a few hundred kpc, which could trigger the high rate of gas loss necessary for a jellyfish morphology to emerge. A theoretical treatment of ram pressure stripping in the environment of galaxy cluster mergers has not been presented in the literature so far; we propose that this could be a common scenario for the formation of jellyfish morphologies in such systems. [ABSTRACT FROM AUTHOR]

We study the effect of inclination on the apparent brightness of star-forming galaxies in spectral passbands that are commonly used as star formation indicators. As diagnostics we use mass-to-light ratios in three passbands: the UV continuum at 280 nm, the Hα emission line, and the FIR 24μ band. We include a study of inclination trends in the IR/UV ratio ('IRX') and the IR/Hα ratio. Our sample comprises a few hundred galaxies from the region around the clusters Abell 901/902 with deep data and inclinations measured from outer discs in Hubble Space Telescope images. As a novelty, the Hα- and separately the N ii emission are measured by tunable-filter imaging and encompass galaxies in their entirety. At galaxy stellar masses above log  M */M⊙ ≳ 10 we find trends in the UV and Hα mass-to-light ratio that suggest an inclination-induced attenuation from face-on to edge-on of ∼1 mag and ∼0.7 mag in UV and Hα, respectively, implying that star formation rates of edge-on galaxies would be underestimated by ∼2.5 × in UV and ∼2 × in Hα. We find the luminosities in UV and Hα to be well correlated, but the optical depth of diffuse dust that causes inclination dependence appears to be lower for stars emitting at 280 nm than for gas clouds emitting Balmer lines. For galaxies with log  M */M⊙ ≲ 9.7, we find no measurable effect at >0.1 mag. The absence of an inclination dependence at 24μ confirms that the average galaxy is optically thin in the FIR. [ABSTRACT FROM AUTHOR]

We conduct a comprehensive projected phase-space analysis of the A901/2 multicluster system at z ~ 0.165. Aggregating redshifts from spectroscopy, tunable-filter imaging and prism techniques, we assemble a sample of 856 cluster galaxies reaching 108.5Mʘ in stellar mass. We look for variations in cluster galaxy properties between virialized and non-virialized regions of projected phase space (PPS). Our main conclusions point to relatively gentle environmental effects, expressedmainly on galaxy gas reservoirs. (1) Stacking the four subclusters in A901/2, we find galaxies in the virialized region are more massive, redder and have marginally higher S´ersic indices, but their half-light radii and Hubble types are not significantly different. (2) After accounting for trends in stellar mass, there is a remaining change in rest-frame colour across PPS. Primarily, the colour difference is due to the absence in the virialized region of galaxies with rest frame B − V < 0.7 and moderate-to-high (M* > 109.85 Mʘ) stellar mass. (3) There is an infalling population of lower mass (M* ≤ 109.85 Mʘ), relatively blue (B − V < 0.7) elliptical or spheroidal galaxies that are strikingly absent in the virialized region. (4) The number of bona fide star-forming and active galactic nucleus galaxies in the PPS regions is strongly dictated by stellar mass. However, there remains a reduced fraction of star-forming galaxies in the centres of the clusters at fixed stellar mass, consistent with the star formation-density relation in galaxy clusters. (5) There is no change in specific Hα-derived star formation rates of star-forming galaxies at fixed mass across the cluster environment. This suggests that pre-processing of galaxies during infall plays a prominent role in quenching star formation. [ABSTRACT FROM AUTHOR]