A near-infrared census of the multi-component stellar structure of early-type dwarf galaxies in the Virgo cluster

TL;DR

This study analyzes the detailed structure of early-type dwarf galaxies in the Virgo cluster using near-infrared imaging, revealing complex multi-component features and their potential environmental origins.

Contribution

It provides the first comprehensive multi-component structural analysis of Virgo cluster dwarf galaxies, highlighting their disk-like features and environmental influences.

Findings

Many dwarf galaxies require multi-component models for accurate light profile fitting.

Inner components are mostly disk-like with Sersic n close to 1.

Structural properties suggest environmental processing affects dwarf galaxy morphology.

Abstract

The fraction of star-forming to quiescent dwarf galaxies varies from almost infinity in the field to zero in the centers of rich galaxy clusters. What is causing this pronounced morphology-density relation? What do quiescent dwarf galaxies look like when studied in detail, and what conclusions can be drawn about their formation mechanism? Here we study a nearly magnitude-complete sample (-19 < M_r < -16 mag) of 121 Virgo cluster early types with deep near-infrared images from the SMAKCED project. We fit two-dimensional models with optional inner and outer components, as well as bar and lens components (in ~15% of the galaxies), to the galaxy images. While a single S\'ersic function may approximate the overall galaxy structure, it does not entirely capture the light distribution of two-thirds of our galaxies, for which multi-component models provide a better fit. This fraction of complex galaxies shows a strong dependence on luminosity, being larger for brighter objects. We analyze the global and component-specific photometric scaling relations of early-type dwarf galaxies and discuss similarities with bright early and late types. The dwarfs' global galaxy parameters show scaling relations that are similar to those of bright disk galaxies. The inner components are mostly fitted with S\'ersic n values close to 1. At a given magnitude they are systematically larger than the bulges of spirals, suggesting that they are not ordinary bulges. We argue that the multi-component structures in early-type dwarfs are mostly a phenomenon inherent to the disks, and may indeed stem from environmental processing.