Photometric properties of the Local Volume dwarf galaxies

Abstract

We present surface photometry and metallicity measurements for 104 nearby dwarf galaxies imaged with the Advanced Camera for Surveys and Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope. In addition, we carried out photometry for 26 galaxies of the sample and for Sextans B on images of the Sloan Digital Sky Survey. Our sample comprises dwarf spheroidal, irregular and transition type galaxies located within ~10 Mpc in the field and in nearby groups: M81, Centaurus A, Sculptor and Canes Venatici I cloud. It is found that the early-type galaxies have on average higher metallicity at a given luminosity in comparison to the late-type objects. Dwarf galaxies with M_B≥-12 to -13 mag deviate towards larger scalelengths from the scalelength-luminosity relation common for spiral galaxies, h∝L^0.5_B. The following correlations between fundamental parameters of the galaxies are consistent with expectations if there is pronounced gas loss through galactic winds: (1) between the luminosity of early-type dwarf galaxies and the mean metallicity of constituent red giant branch stars, Z~L^0.4, (2) between mean surface brightness within the 25 mag arcsec^-2 isophote and the corresponding absolute magnitude in the V and I bands, SB ₂₅~ 0.3M₂₅ and (3) between the central surface brightness (or effective surface brightness) and integrated absolute magnitude of galaxies in the V and I bands, SB₀~ 0.5M_L, SB _e~ 0.5 M_e. The knowledge of basic photometric parameters for a large sample of dwarf galaxies is essential for a better understanding of their evolution.