Gas distribution in the Local Group: absorption patterns through observations and cosmological simulations

CECILIA SCANNAPIECO; MARTÍN CARUSSO; SEBASTIÁN E. NUZA

Buenos Aires

Conferencia; Dark Side of the Universe 2019; 2019

MinCyT, CONICET, UBA, ICTP

The relationship between galaxies and cosmology is an important aspect in their formation, which not only manifests itself in their properties at different cosmological times, but also in their relationship with the environment in which their formation takes place. Due to observational constraints, our Local Group is the best candidate to study the relationship between galaxy formation and larger scales, since information on the gas distribution in haloes and the Intergalactic medium can be obtained from absorption spectra that account for the density, composition and velocity of the ionized gaseous material. In order to study the Local Group's gaseous phase, the use hydrodynamical numerical simulations in a cosmological context is key to understand and guide observations. In the present work, we implement a method for the generation of synthetic absorption spectra from Local Group simulations; and we generate a sample of simulated observations from the sun's position. We obtain significant differences between sightlines in the MW-M31 and other directions, in terms of gas density and velocity. These support the hypothesis of the existence of a gas bridge in the region between MW and M31. Comparing trends in the covering fraction of HVCs (high velocity clouds) with their corresponding observations, we notice that the best agreement takes place by selecting a velocity threshold of 30-45 km/s, as opposed to the observational value of 100 km/s. Lastly, we study the distribution of gas in M31 and dwarf galaxies from the Local Group. The obtained results are in agreement with observations: evidence for an extended gaseous halo holds only in the case of M31.