Fernandez Figueroa

Observing the baryon cycle using Mg II ultra-strong absorbers

The gas surrounding galaxies, also known as the circumgalactic medium (CGM), is a giant reservoir believed to host 50% of the baryonic matter in the Universe. Unfortunately, the CGM is usually too diffuse to be studied in emission, so it is observed through absorption lines in background QSOs. It has been well studied that the Mg II absorption strength of the CGM decreases with distance from the centre of its host galaxy, however, there is a population of absorbers that seem to defy this notion: the Mg II ultra-strong absorbers. These absorbers have a rest-frame equivalent width higher than 3 Å, independent of their impact parameter. Two hypotheses have arisen to explain these phenomena: (1) galaxy mergers produce them, or (2) they come from star-formation driven outflows. We have a sample of five Mg II ultra-strong absorbers associated with isolated galaxies, meaning that the ultra-strong absorption must come from outflows. However, only one of the galaxies seems to be currently driving outflows. Moreover, three of the galaxies are presently going through strong accretion events. In this talk, I will discuss all the processes the CGM of these galaxies goes through, along with understanding the origin of the observed ultra-strong absorption.