Forming Blue Compact Dwarf Galaxy (BCD) through Mergers

Abstract

It has long been speculated that Blue Compact Dwarf galaxies (BCDs) are formed through the interaction between low-mass gas-rich galaxies, but a few candidates of such systems have been studied in detail. We study a sample of compact star-forming dwarf galaxies that are selected from a merging dwarf galaxy catalog. We present a detailed study of their spectroscopic and structural properties. We find that these BCDs looking galaxies host extended stellar shells and thus are confirmed to be a dwarf-dwarf merger. Their stellar masses range between $8\times10^7$~M$_{\sun}$ and $2\times10^9$~M$_{\sun}$. Although the extended tail and shell are prominent in the deep optical images, the overall major axis light profile is well modeled with a two-component S\'ersic function of inner compact and extended outer radii. We calculate the inner and outer component stellar-mass ratio using the two-component modeling. We find an average ratio of 4:1 (with a range of 10:1 to 2:1) for our sample, indicating that the central component dominates the stellar mass with an ongoing burst of star-formation. From the measurement of H$_\alpha$ equivalent width, we derived the star-formation ages of these galaxies. The derived star-formation ages of these galaxies turn out to be in the order of a few 10 Myr, suggesting the recent ignition of star-formation due to events of satellite interaction.