Surface Photometry of Dwarf Irregular Galaxies in Different Environments

Surface photometry data on 90 dwarf irregular galaxies (dIrrs) in a wide vicinity of the Virgo cluster and 30 isolated dIrrs are presented. Images from the Sloan Digital Sky Survey (SDSS) are used. The following mean photometric characteristics (color and central surface brightness) are obtained for objects in the two samples: (V - I)(0) = 0.75 (sigma = 0.19), (B - V)(0) = 0.51 (sigma = 0.13), SBV = 22.16 (sigma = 1.02) for the dIrrs in the vicinity of the Virgo cluster and (V - I)(0) = 0.66 (sigma = 0.43), (B - V)(0) = 0.57 (sigma = 0.16), and SBV = 22.82 (sigma = 0.73) for the isolated galaxies. The mean central surface brightnesses for the isolated galaxies in this sample are significantly lower than for the dIrrs in a denser environment. The average color characteristics of the dIrrs in the different environments are the same to within 0.2 mag.