5 research outputs found
Unveiling a Rich System of Faint Dwarf Galaxies in the Next Generation Fornax Survey
We report the discovery of 158 previously undetected dwarf galaxies in the
Fornax cluster central regions using a deep coadded and -band image
obtained with the DECam wide-field camera mounted on the 4-meter Blanco
telescope at the Cerro Tololo Interamerican Observatory as part of the {\it
Next Generation Fornax Survey} (NGFS). The new dwarf galaxies have
quasi-exponential light profiles, effective radii kpc and
average effective surface brightness values mag
arcsec. We confirm the existence of ultra-diffuse galaxies (UDGs) in the
Fornax core regions that resemble counterparts recently discovered in the Virgo
and Coma galaxy clusters.~We also find extremely low surface brightness NGFS
dwarfs, which are several magnitudes fainter than the classical UDGs. The
faintest dwarf candidate in our NGFS sample has an absolute magnitude of
\,mag. The nucleation fraction of the NGFS dwarf galaxy sample
appears to decrease as a function of their total luminosity, reaching from a
nucleation fraction of at luminosities brighter than
mag to at luminosities fainter than
mag. The two-point correlation function analysis of the
NGFS dwarf sample shows an excess on length scales below kpc,
pointing to the clustering of dwarf galaxies in the Fornax cluster core.Comment: 6 pages, 3 figures. Accepted for publication in The Astrophysical
Journal Letters. Download the high-resolution version of the paper from the
following link: https://www.dropbox.com/s/xb9vz8s29wlzjgf/ms.pdf?dl=
Spectroscopy of NGC 4258 Globular Cluster Candidates:Membership Confirmation and Kinematics
We present multi-object spectroscopic observations of 23 globular cluster
candidates (GCCs) in the prototypical megamaser galaxy NGC 4258, carried out
with the OSIRIS instrument at the 10.4 m Gran Telescopio Canarias. The
candidates have been selected based on the () versus
() diagram, in the first application of the uiks-method to a
spiral galaxy. In the spectroscopy presented here, 70% of the candidates are
confirmed as globular clusters. Our results validate the efficiency of the
uiks-method in the sparser GC systems of spirals, and given the downward
correction to the total number of GCs, the agreement of the galaxy with the
correlations between black hole mass, and total number and mass of GCs is
actually improved. We find that the GCs, mostly metal-poor, co-rotate with the
HI disk, even at large galactocentric distances.Comment: 25 pages, 15 figures; accepted for publication in The Astrophysical
Journa
A Virgo Environmental Survey Tracing Ionised Gas Emission. VESTIGE VIII. Bridging the cluster-ICM-galaxy evolution at small scales
15 pages, 7 images, 4 tables. Accepted on A\&AWe measure FIR emission from tails of stripped dust following the ionised and atomic gas components in galaxies undergoing ram pressure stripping. We study the dust-to-gas relative distribution and mass ratio in the stripped interstellar medium and relate them to those of the intra-cluster medium, thus linking the cluster-ICM-galaxy evolution at small-scales. The galaxy sample consists of three Scd Virgo galaxies with stellar masses in the range , and within 1 Mpc from the cluster centre, namely NGC 4330, NGC 4522, and NGC 4654. Through the analysis of VESTIGE H, SPIRE far-infrared, and VIVA HI data, we trace the spatial distribution of the tails and infer the dust and gas masses from the measured far-infrared 250 m and HI flux densities. Dust-to-gas mass ratios (DGRs) in the tails are analysed as a function of the galaxy mass, metallicity, and dust temperature. Along the stripped component, the dust distribution closely follows the HI and H emitting gas, all extending beyond the optical disc. In these regions, the DGRs are , , and , for NGC 4330, NGC 4522, and NGC 4654, respectively, i.e. up to a factor of 15 less than the values measured in the main body of nearby galaxies. We also find a negative trend in the DGR as a function of the metallicity that can be explained in terms of a dust component more centrally concentrated in more metal-rich systems. Together with the finding that the stripped dust is cold, , our results support an outside-in stripping scenario of the galaxy interstellar medium. This study shows that ram pressure stripping is a key mechanism in the building up of the Virgo intra-cluster component injecting dust grains into the ICM, thus contributing to its metal enrichment
The Next Generation Virgo Cluster Survey. XXXIV. Ultracompact Dwarf Galaxies in the Virgo Cluster
International audienceWe present a study of ultra compact dwarf (UCD) galaxies in the Virgo cluster based mainly on imaging from the Next Generation Virgo Cluster Survey (NGVS). Using ∼100 deg 2 of u * giz imaging , we have identified more than 600 candidate UCDs, from the core of Virgo out to its virial radius. Candidates have been selected through a combination of magnitudes, ellipticities, colors, surface bright-nesses, half-light radii and, when available, radial velocities. Candidates were also visually validated from deep NGVS images. Subsamples of varying completeness and purity have been defined to explore the properties of UCDs and compare to those of globular clusters and the nuclei of dwarf galaxies with the aim of delineating the nature and origins of UCDs. From a surface density map, we find the UCDs to be mostly concentrated within Virgo's main subclusters, around its brightest galaxies. We identify Corresponding author: Chengze Liu [email protected] arXiv:2007.15275v1 [astro-ph.GA] 30 Jul 2020 2 Liu et al. several subsamples of UCDs-i.e., the brightest, largest, and those with the most pronounced and/or asymmetric envelopes-that could hold clues to the origin of UCDs and possible evolutionary links with dwarf nuclei. We find some evidence for such a connection from the existence of diffuse envelopes around some UCDs, and comparisons of radial distributions of UCDs and nucleated galaxies within the cluster