Structural analysis of star-forming blue early-type galaxies:
  Merger-driven star formation in elliptical galaxies
  Star-forming blue early-type galaxies at low redshift can give insight to the
stellar mass growth of L$*$ elliptical galaxies in the local Universe. We wish
to understand the reason for star formation in these otherwise passively
evolving red and dead stellar systems. The fuel for star formation can be
acquired through recent accretion events such as mergers or flyby. The
signatures of such events should be evident from a structural analysis of the
galaxy image. We carried out structural analysis on SDSS $r$-band imaging data
of 55 star-forming blue elliptical galaxies, derived the structural parameters,
analysed the residuals from best-fit to surface brightness distribution, and
constructed the galaxy scaling relations. We found that star-forming blue
early-type galaxies are bulge-dominated systems with axial ratio $>$ 0.5 and
surface brightness profiles fitted by Sersic profiles with index ($n$) mostly
$>$ 2. Twenty-three galaxies are found to have $n$ $<$ 2; these could be
hosting a disc component. The residual images of the 32 galaxy surface
brightness profile fits show structural features indicative of recent
interactions. The star-forming blue elliptical galaxies follow the Kormendy
relation and show the characteristics of normal elliptical galaxies as far as
structural analysis is concerned. There is a general trend for high-luminosity
galaxies to display interaction signatures and high star formation rates. The
star-forming population of blue early-type galaxies at low redshifts could be
normal ellipticals that might have undergone a recent gas-rich minor merger
event. The star formation in these galaxies will shut down once the recently
acquired fuel is consumed, following which the galaxy will evolve to a normal
early-type galaxy.
