Early-type dwarf galaxies with multicomponent stellar structure: Are they remnants of disc galaxies strongly transformed by their environment?

Abstract

The surface brightness distribution of $\sim$30-40$\%$ of the early-type dwarf galaxies with $-18 \leq M_{B} \leq -15$ in the Virgo and the Coma clusters is fitted by models that include two structural components (S\`ersic + exponential) as for bright disc galaxies.The goal of the present study is to determine whether early-type dwarf galaxies with a two-component stellar structure in the Virgo and the Coma clusters are low-luminosity copies of bright disc galaxies or are the remnants of bright galaxies strongly transformed by cluster environmental effects.I analysed the location of bright disc galaxies and early-type dwarfs in the $r_{b,e}/h$- $n$ plane. The location in this plane of the two-component dwarf galaxies was compared with the remnants of tidally disrupted disc galaxies reported by numerical simulations. Bright unbarred disc galaxies show a strong correlation in the $r_{b,e}/h$-$n$ plane. Galaxies with larger S\`ersic shape parameters show a higher $r_{b,e}/h$ ratio. In contrast, two-component early-type dwarf galaxies do not follow the same correlation. A fraction ($\sim$55%) of them are located outside the locus defined in this plane by having 95$\%$ of bright disc galaxies. This distribution indicates that they are not a low-mass replica of bright disc galaxies. The different location in the $r_{b,e}/h$- $n$ plane of two-component early-type dwarfs and bright galaxies can be qualitatively explain whether the former are remnants of disc galaxies strongly transformed by tidal processes.The progenitors of $\sim$20-25% of early-type dwarf galaxies with $-18 \leq M_{B} \leq -15$ in the Virgo and Coma clusters could be bright disc galaxies transformed by effects of the environment. These tidally transformed galaxies can be selected according to their location in the $r_{b,e}/h$-$n$ plane.