Role of environment in the origin of early-type dwarf galaxies

Role of environments is one of today's most widely discussed and debated topic in the field of extra-galactic astronomy. Extreme morphology-density relations found in low-mass galaxies are considered to be the result of an effective role played by environment in the evolution of these galaxies. I will present the results from our dedicated study of early-type dwarf galaxies (dEs) in different environments using imaging and spectroscopic data. We find that Virgo cluster dEs have a variety of structural and kinematic properties. A significant fraction of dEs possesses disk features, such as spiral arm and bar, while a central nucleus seems to be universal in these low mass galaxies. We also find that a majority of dEs are fast rotator and their rotation curves are much steeper than that of spiral galaxies of similar mass. Finally I will discuss how the different environmental mechanisms, i.e., gas-stripping or tidal interaction, can contribute to form heterogeneous dEs in Virgo cluster.