by Federico Lelli (CWRU)

Tidal Dwarf Galaxies (TDGs) are recycled objects that form within the collisional debris around interacting/merging galaxies. Lelli et al. (2015) investigate the gas dynamics in a sample of six TDGs and find they can be described by rotating disc models. These TDGs also appear to be devoid of non-baryonic dark matter, as expected from numerical simulations in a LCDM cosmology. The image above shows three interacting systems (NGC 4694, NGC 5291, and NGC 7252) and their bona-fide TDGs (in yellow). Optical images are overlaid with UV emission from GALEX (pink) and HI emission from the VLA (blue).

Reference: Lelli, Duc, Brinks, Bournaud, McGaugh, Lisenfeld, Weilbacher, Boquien, Revaz, Braine, Koribalski, and Belles 2015, A&A, in press