Warrick J Couch | Searcharxiv

arXiv2019

An Ultra diffuse Galaxy in the NGC 5846 group from the VEGAS survey

Many ultra diffuse galaxies (UDGs) have now been identified in clusters of galaxies. However, the number of nearby UDGs suitable for detailed follow-up remain rare. Our aim is to begin to identify UDGs in the environments of nearby bright early-type galaxies from the VEGAS survey. Here we use a deep g band image of the NGC 5846 group, taken as part of the VEGAS survey, to search for UDGs. We found one object with properties of a UDG if it associated with the NGC 5846 group, which seems likely. The galaxy, we name NGC 5846$\_$UDG1, has an absolute magnitude of M$_g$ = -14.2, corresponding to a stellar mass of $\sim$10$^8$ M$_{\odot}$. It also reveals a system of compact sources which are likely globular clusters. Based on the number of globular clusters detected we estimate a halo mass that is greater than 8$\times$10$^{10}$ M$_{\odot}$ for UDG1.

astro-ph.GA↗

arXiv2003

The Morphological decomposition of Abell A868

We report on the morphological luminosity functions (LFs) and radial profiles derived for the galaxy population within the rich cluster Abell 868 (z=0.153) based purely on Hubble Space Telescope Imaging in F606W. We recover Schechter functions for early(E/S0)-, mid(Sabc)- and late(Sd/Irr)- type galaxies. The early-, mid- and late- types are all consistent with the recent field morphological LFs based on recent analysis of the Sloan Digital Sky Survey -- Early Data Release (SDSS-EDR; Nakamura et al 2003). From a detailed error analysis, including clustering of the background population, we note that improved statistics can only come from combining data from many clusters. We also examine the luminosity-density and number-density profiles as a function of morphology and draw the following conclusions: (1) The galaxies responsible for the steep faint-end slope are predominantly of late-type morphology, (2) The cluster core is dominated by elliptical galaxies, (3) The core is devoid of late-types systems, (4) The luminosity-density as a function of morphological type is skewed towards early-types when compared to the field, (5) Up to half of the elliptical galaxies may have formed from the spiral population through core disk-destruction process(es). We believe the most plausible explanation is the conventional one that late-types are destroyed during transit through the cluster core and that mid-types are converted into early-types through a similar process, which destroys the outer disk and results in a more tightly bound population of core ellipticals.[Abridged].

astro-ph↗