Dmitry I. Makarov — Page 2

arXiv2005

Hubble Space Telescope Imaging of Globular Cluster Candidates in Low Surface Brightness Dwarf Galaxies

Fifty-seven nearby low surface brightness dwarf galaxies were searched for globular cluster candidates (GCCs) using Hubble Space Telescope WFPC2 imaging in V and I. The sample consists of 18 dwarf spheroidal (dSph), 36 irregular (dIrr), and 3 "transition" type (dIrr/dSph) galaxies with angular sizes less than 3.7 kpc situated at distances 2-6 Mpc in the field and in the nearby groups: M81, Centaurus A, Sculptor, Canes Venatici I cloud. We find that ~50% of dSph, dIrr/dSph, and dIrr galaxies contain GCCs. The fraction of GCCs located near the center of dwarf spheroidal galaxies is >2 times higher than that for dIrrs. The mean integral color of GCCs in dSphs, V-I = 1.04+/-0.16 mag, coincides with the corresponding value for Galactic globular clusters and is similar to the blue globular cluster sub-populations in massive early-type galaxies. The color distribution for GCCs in dIrrs shows a clear bimodality with peaks near V-I = 0.5 and 1.0 mag. Blue GCCs are presumably young with ages t < 1 Gyr, while the red GCC population is likely to be older. The detected GCCs have absolute visual magnitudes between M_V = -10 and -5 mag. We find indications for an excess population of faint GCCs with M_V > -6.5 mag in both dSph and dIrr galaxies, reminiscent of excess populations of faint globular clusters in nearby Local Group spiral galaxies. The measurement of structural parameters using King-profile fitting reveals that most GCCs have structural parameters similar to extended outer halo globular clusters in the Milky Way and M31, as well as the recently discovered population of "faint fuzzy" clusters in nearby lenticular galaxies.

astro-ph↗

arXiv2004

Catalog of Nearby Galaxies and the Local Cosmic Web

We compiled an all-sky catalog of 451 nearby galaxies, each having an individual distance estimate $D \la 10$ Mpc or the radial velocity $V_{LG} < 550$ km s$^{-1}$. The catalog contains data on basic optical and HI properties of the galaxies: their diameters, absolute magnitudes, morphological types, optical and HI surface brightnesses, rotational velocities, indicative mass-to-luminosity and HI mass-to-luminosity ratios, as well as a so-called "tidal index", which quantifies the galaxy environment. We expect the catalog completeness to be $\sim75$% within 8 Mpc. About 85% of the Local volume population are dwarf (dIrr, dIm, dSph) galaxies with $M_B>-17.0$, which contribute about 4% to the local luminosity density, and $\sim(10-16)$% to the local HI mass density. We found that the mean local barion density $Ω_b(<8$ Mpc) = 2.3% consists of only a half of the global barion density, $Ω_b=(4.7\pm0.6)$% (Spergel et al. 2003). The mean-square pairwise difference of radial velocities is about 100 km s$^{-1}$ for spatial separations within 1 Mpc, increasing to $\sim 300$ km s$^{-1}$ on a scale of $\sim 3$ Mpc.

astro-ph↗