A VST and VISTA study of globular clusters in NGC253

Aims. We analyze the properties of the sources in the NGC253 to define an up to date catalog of GC candidates in the galaxy. Methods. Our analysis is based on the science verification data of two ESO survey telescopes, VST and VISTA. Using ugri photometry from VST and JKs from VISTA, GC candidates were selected using the morpho-photometric and color properties of spectroscopically confirmed GCs available in the literature. The strength of the results was verified against available archival HST/ACS data from the GHOSTS survey. Results. The adopted GC selection leads to the definition of a sample of ~350 GC candidates. At visual inspection, we find that 82 objects match all the requirements for selecting GC candidates and 155 are flagged as uncertain GC candidate; 110 are unlikely GCs, most likely background galaxies. Furthermore, our analysis shows that four of the previously spectroscopically confirmed GCs, i.e., ~20% of the total spectroscopic sample, are more likely either background galaxies or high-velocity Milky Way stars. The radial density profile of the selected best candidates shows the typically observed r1/4-law radial profile. The analysis of the color distributions reveals only marginal evidence of the presence of color bimodality, which is normally observed in galaxies of similar luminosity. The GC luminosity function does not show the typical symmetry, mainly because of the lack of bright GCs. Part of the bright GCs missing might be at very large galactocentric distances or along the line of sight of the galaxy dusty disk. Conclusions. Using ugriJKs photometry we purged the list of GCs with spectroscopic membership and photometric GC candidates in NGC 253. Our results show that the use of either spectroscopic or photometric data only does not generally ensure a contaminant-free sample and a combination of both spectroscopy and photometry is preferred.Comment: 24 pages, 15 figures, Accepted by Astronomy and Astrophysic

The distance to NGC1316 (Fornax A): yet another curious case

The distance of NGC1316, the brightest galaxy in Fornax, is an interesting test for the cosmological distance scale. First, because Fornax is the 2nd largest cluster of galaxies at <~25 Mpc after Virgo and, in contrast to Virgo, has a small line-of-sight depth; and second, because NGC1316 is the galaxy with the largest number of detected SNeIa, giving the opportunity to test the consistency of SNeIa distances internally and against other indicators. We measure SBF mags in NGC1316 from ground and space-based imaging data, providing a homogeneous set of measurements over a wide wavelength interval. The SBF, coupled with empirical and theoretical calibrations, are used to estimate the distance to the galaxy. We present the first B-band SBF measurements of NGC1316 and use them together with the optical and near-IR SBF data to analyze the properties of field stars. Our distance modulus m-M=31.59 +-0.05(stat) +-0.14(sys), when placed in a consistent Cepheid distance scale, agrees with the results from other indicators. However, our result is ~17% larger than the most recent estimate based on SNeIa. Possible explanations for this disagreement are the uncertainties on internal extinction, or calibration issues. Concerning the stellar population analysis, we confirm earlier results from other indicators: the field stars in NGC1316 are dominated by a solar metallicity, intermediate age component. A substantial mismatch exists between B-band SBF models and data, a behavior that can be accounted for by an enhanced percentage of hot horizontal branch stars. Our study of the SBF distance to NGC1316, and the comparison with distances from other indicators, raises some concern about the homogeneity between the calibrations of different indicators. If not properly placed in the same reference scale, significant differences can occur, with dramatic impact on the cosmological distance ladder.Comment: 21 pages, 13 figures; A&A accepte

VEGAS: A VST Early-type GAlaxy Survey. III. Mapping the galaxy structure, interactions and intragroup light in the NGC 5018 group

Most of the galaxies in the Universe at present day are in groups, which are key to understanding the galaxy evolution. In this work we present a new deep mosaic of 1.2 x 1.0 square degrees of the group of galaxies centered on NGC 5018, acquired at the ESO VLT Survey Telescope. We use u, g, r images to analyse the structure of the group members and to estimate the intra-group light. Taking advantage of the deep and multiband photometry and of the large field of view of the VST telescope, we studied the structure of the galaxy members and the faint features into the intra-group space and we give an estimate of the intragroup diffuse light in the NGC 5018 group of galaxies. We found that ~ 41% of the total g-band luminosity of the group is in the form of intragroup light (IGL). The IGL has a (g - r) color consistent with those of other galaxies in the group, indicating that the stripping leading to the formation of IGL is ongoing. From the study of this group we can infer that there are at least two different interactions involving the group members: one between NGC 5018 and NGC 5022, which generates the tails and ring-like structures detected in the light, and another between NGC 5022 and MCG-03-34-013 that have produced the HI tail. A minor merging event also happened in the formation history of NGC 5018 that have perturbed the inner structure of this galaxy.Comment: 21 pages, 15 figures. Accepted for publication in Ap

An Interacting Galaxy Pair at the Origin of a Light Echo

In a low-density region of the Shapley supercluster we identified an interacting galaxy pair at redshift z = 0.04865 in which the Seyfert 2 nucleus of the main galaxy (ShaSS 073) is exciting an extended emission line region (EELR, ∼170 kpc^2) in the disk of the less massive companion (ShaSS 622). New integral-field spectroscopy and the multiband data set, spanning from far-ultraviolet to far-infrared and radio wavelengths, allowed us to obtain a detailed description of the ShaSS 622-073 system. The gas kinematics shows hints of interaction, although the overall velocity field shows a quite regular rotation in both galaxies, thus suggesting that we are observing their first encounter as confirmed by the estimated distance of 21 kpc between the two galaxy centers. The detected ∼ 2-3 kpc active galactic nucleus (AGN) outflow and the geometry of the EELR in ShaSS 622 support the presence of a hollow bicone structure. The status and sources of the ionization across the whole system have been analyzed through photoionization models and a Bayesian approach that prove a clear connection between the AGN and the EELR. The luminosity of the AGN (2.4×10^44 erg/s) is a factor of 20 lower than the power needed to excite the gas in the EELR (4.6 ×10^45 erg/s), indicating a dramatic fading of the AGN in the past 3×10^4 yr. ShaSS 073-622 provides all the ingredients listed in the recipe of a light echo where a highly-ionized region maintains memory of a preceding more energetic phase of a now-faded AGN. This is the first case of a light echo observed between two galaxies

In the Shade of Dorado Group Giants: Tracing the Eventful Life of Member Galaxies in Optical and Far UV

Groups are key to understand the galaxy evolution: they contain most of the galaxies in Universe at present day, most of the stellar mass and have their own way to transform galaxies from active to passive. Our aim is understanding the mechanisms driving the co-evolution of galaxies in nearby groups. Rich of early-type galaxies showing shells and FUV bright rings, Dorado is a nearby (16.9 Mpc Firth et al. 2006, MNRAS, 372, 1856) loose (about 10 deg2 , Carrasco et al 2001, AJ, 121, 148) association still non-virialized, likely a way station towards rich, virialized groups. We are mapping the group via deep VST g, r SDSS filters and (hopefully) Astrosat-UVIT; Far and Near UV imaging from GALEX and Swift-UVOT are also available. Our targets include the giant earlytype galaxies (ETGs) marking the group backbone as well as their intermediate companions and dwarfs whose luminosity function is still largely incomplete. The optical and Far UV analysis is shedding light on the Dorado evolving phase, showing residual star formation in evolved giant ETGs

The Fornax Deep Survey data release 1

We present the first data release of the Fornax Deep Survey (FDS), animaging survey using using the wide-field imager OmegaCAM mounted on theVST in the SDSS u', g', r', and i'-bands covering the Fornax GalaxyCluster and the infalling Fornax A Group. FDS is a joint project betweenNOVA (previously called FOCUS - PI: R. F. Peletier) and INAF (as part ofVEGAS - PIs: M. Capaccioli and E. Iodice). With exposure times of about9 hours over an area of ~28 square degrees, this survey is a legacydataset for studies of members of the Fornax Galaxy Cluster and theinfalling Fornax A Group down to a surface brightness limit of ~28mag/arcsec^2 (1-sigma surface brightness over a 1 arcsecond^2 area) andopens a new parameter regime to investigate the role of the clusterenvironment in shaping the properties of its galaxy population. Afterthe Virgo cluster,Fornax is the second nearest galaxy cluster to us, andwith its different mass and evolutionary state, it provides a valuablecomparison that makes it possible to understand the various evolutionaryeffects on galaxies and galaxy clusters. Details about the survey can befound in A. Venhola, R. F. Peletier, E. Laurikainen et al., 2018,A&amp;A 620, 165. In this release, 181 Gb of (compressed) fits filesreduced using the system are present. Catalogues with the completesample of sources including dwarf galaxies part of the cluster, globularclusters, and background galaxies will be provided in forthcomingreleases. The data products are available via the ESO Science Portal athttps://archive.eso.org/scienceportal/home?publ_date=2020-08-2

The Fornax Deep Survey data release 1

We present the first data release of the Fornax Deep Survey (FDS), an imaging survey using using the wide-field imager OmegaCAM mounted on the VST in the SDSS u', g', r', and i'-bands covering the Fornax Galaxy Cluster and the infalling Fornax A Group. FDS is a joint project between NOVA (previously called FOCUS - PI: R. F. Peletier) and INAF (as part of VEGAS - PIs: M. Capaccioli and E. Iodice). With exposure times of about 9 hours over an area of ~28 square degrees, this survey is a legacy dataset for studies of members of the Fornax Galaxy Cluster and the infalling Fornax A Group down to a surface brightness limit of ~28 mag/arcsec^2 (1-sigma surface brightness over a 1 arcsecond^2 area) and opens a new parameter regime to investigate the role of the cluster environment in shaping the properties of its galaxy population. After the Virgo cluster,Fornax is the second nearest galaxy cluster to us, and with its different mass and evolutionary state, it provides a valuable comparison that makes it possible to understand the various evolutionary effects on galaxies and galaxy clusters. Details about the survey can be found in A. Venhola, R. F. Peletier, E. Laurikainen et al., 2018, A&A 620, 165. In this release, 181 Gb of (compressed) fits files reduced using the system are present. Catalogues with the complete sample of sources including dwarf galaxies part of the cluster, globular clusters, and background galaxies will be provided in forthcoming releases. The data products are available via the ESO Science Portal at https://archive.eso.org/scienceportal/home?publ_date=2020-08-26Comment: arXiv admin note: substantial text overlap with arXiv:1810.0055

The Fornax Deep Survey data release 1

We present the first data release of the Fornax Deep Survey (FDS), an imaging survey using using the wide-field imager OmegaCAM mounted on the VST in the SDSS u', g', r', and i'-bands covering the Fornax Galaxy Cluster and the infalling Fornax A Group. FDS is a joint project between NOVA (previously called FOCUS - PI: R. F. Peletier) and INAF (as part of VEGAS - PIs: M. Capaccioli and E. Iodice). With exposure times of about 9 hours over an area of ~28 square degrees, this survey is a legacy dataset for studies of members of the Fornax Galaxy Cluster and the infalling Fornax A Group down to a surface brightness limit of ~28 mag/arcsec^2 (1-sigma surface brightness over a 1 arcsecond^2 area) and opens a new parameter regime to investigate the role of the cluster environment in shaping the properties of its galaxy population. After the Virgo cluster,Fornax is the second nearest galaxy cluster to us, and with its different mass and evolutionary state, it provides a valuable comparison that makes it possible to understand the various evolutionary effects on galaxies and galaxy clusters. Details about the survey can be found in A. Venhola, R. F. Peletier, E. Laurikainen et al., 2018, A&A 620, 165. In this release, 181 Gb of (compressed) fits files reduced using the system are present. Catalogues with the complete sample of sources including dwarf galaxies part of the cluster, globular clusters, and background galaxies will be provided in forthcoming releases. The data products are available via the ESO Science Portal at https://archive.eso.org/scienceportal/home?publ_date=2020-08-26Comment: arXiv admin note: substantial text overlap with arXiv:1810.0055