Birth, life and survival of Tidal Dwarf Galaxies

TL;DR

This paper reviews the formation, survival, and identification challenges of Tidal Dwarf Galaxies, highlighting recent observational and simulation advances, and discussing their uncertain cosmological significance.

Contribution

It synthesizes recent multi-wavelength observations and simulations to clarify the properties and origins of TDGs, and presents new examples of old TDGs around a nearby elliptical galaxy.

Findings

Identification of specific properties of TDGs such as location, dark matter, and metal content.

Recent discovery of genuine old TDGs around a nearby elliptical galaxy.

Ongoing debate about the cosmological importance and definition of TDGs.

Abstract

Advances on the formation and survival of the so-called Tidal Dwarf Galaxies (TDGs) are reviewed. The understanding on how objects of the mass of dwarf galaxies may form in debris of galactic collisions has recently benefited from the coupling of multi-wavelength observations with numerical simulations of galaxy mergers. Nonetheless, no consensual scenario has yet emerged and as a matter of fact the very definition of TDGs remains elusive. Their real cosmological importance is also a matter of debate, their presence in our Local Group of galaxies as well. Identifying old, evolved, TDGs among the population of regular dwarf galaxies and satellites may not be straightforward. However a number of specific properties (location, dark matter and metal content) that objects of tidal origin should have are reminded here. Examples of newly discovered genuine old TDGs around a nearby elliptical galaxy are finally presented.