Morphological transformations of Dwarf Galaxies in the Local Group

TL;DR

This paper reviews how various dynamical processes in the Local Group influence the morphological evolution of dwarf galaxies, suggesting they may follow transformation chains from irregular to spheroidal or elliptical types.

Contribution

It proposes a framework linking dwarf galaxy morphologies to dynamical transformation processes, highlighting evolutionary paths in the Local Group.

Findings

Dwarf galaxy types are distributed spatially within the Local Group.

Morphological signatures indicate past dynamical interactions.

Evolutionary paths from irregular to spheroidal types are identified.

Abstract

In the Local Group there are three main types of dwarf galaxies: Dwarf Irregulars, Dwarf Spheroidals, and Dwarf Ellipticals. Intermediate/transitional types are present as well. This contribution reviews the idea that the present day variety of dwarf galaxy morphologies in the Local Group might reveal the existence of a transformation chain of events, of which any particular dwarf galaxy represents a manifestation of a particular stage. In other words, all dwarf galaxies that now are part of the Local Group would have formed identically in the early universe, but then evolved differently because of morphological transformations induced by dynamical processes like galaxy harassment, ram pressure stripping, photo-evaporation, and so forth. We start describing the population of dwarf galaxies and their spatial distribution in the LG. Then, we describe those phenomena that can alter the morphology of a dwarf galaxies, essentially by removing, partially or completely, their gas content. Lastly, we discuss morphological signatures in the Local Group Dwarf Galaxies that can be attributed to different dynamical phenomena. While it is difficult to identify a unique and continuous transformation sequence, we have now a reasonable understanding of the basic evolutionary paths that lead to the various dwarf galaxy types.