Formation and Evolution of Dwarf Elliptical Galaxies

TL;DR

This thesis investigates the origin and evolution of dwarf elliptical galaxies through new spectral analysis methods and observational data, revealing their connection to dwarf irregulars and identifying ram pressure stripping as a key gas removal process.

Contribution

It introduces a novel spectral fitting technique for stellar populations and kinematics, and applies it to observational data, providing new insights into dE galaxy evolution.

Findings

Discovery of young nuclei in Virgo dE galaxies

Evidence supporting an evolutionary link between dE and dIrr galaxies

Identification of ram pressure stripping as the main gas removal mechanism

Abstract

This thesis presents observational studies of evolution of dwarf elliptical galaxies. dE's are numerically dominant population in clusters of galaxies, but their origin and evolution is a matter of debate. Several scenarios of gas removal from dE's exist: galactic winds, ram pressure stripping, gravitaional harassment. We present new method to estimate stellar population parameters and internal kinematics, based on fitting observed spectra in the pixel space by PEGASE.HR synthetic populations. We apply this technique to 3D-spectroscopic observations of dE galaxies in the Virgo cluster and nearby groups and multiobject spectroscopy of several dozens of dE's in the Abell 496 cluster. We present discovery of young nuclei in bright dE galaxies in the Virgo cluster. Based on the analysis of observational data we conclude that: (1) there is an evolutionary connection between dE's and dIrr's, (2) the most probable scenario of gas removal is ram pressure stripping by the intergalactic medium.