Forming Blue Compact Dwarf Galaxy (BCD) through Mergers

TL;DR

This paper provides evidence that Blue Compact Dwarf galaxies are formed through dwarf-dwarf mergers, characterized by extended stellar shells and a dominant central star-forming component, with recent starburst activity triggered by interactions.

Contribution

It offers detailed spectroscopic and structural analysis of merging dwarf galaxies, confirming their merger origin and quantifying their stellar mass ratios and star-formation ages.

Findings

BCDs host extended stellar shells indicating dwarf-dwarf mergers.

The inner component dominates the stellar mass with a 4:1 average ratio.

Star-formation ages are a few 10 Myr, indicating recent starburst ignition.

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.