The evolution of the dust and gas content in galaxies
Astronomy and astrophysics
Friday 06 March 2015
to 11:30 at
Paola Santini (INAF, Rome)
By means of Herschel observations, we have studied the scaling relations in place between gas, dust, stellar mass (Mstar) and star formation rate, as well as their evolution from z~2.5 to the current day. The gas mass is estimated from dust mass measurements by adopting assumptions on the dust-to-gas ratio. The inferred relation between the star formation rate and gas mass (known as the integrated Schmidt-Kennicutt relation) for the bulk of the population is in good agreement with previous results based on CO measurements, despite the completely different approaches. This confirms the reliability of this method, applicable to much larger samples of galaxies. In order to resolve the degeneracies associated with the Main Sequence (MS) relation, dust and gas evolution have been investigated by disentangling the effects of stellar mass and star formation rate. We
observe no evolution in the gas fraction with redshift once the stellar mass and star formation rate are fixed. We explain these trends by introducing a universal relation between the gas fraction, stellar mass and star formation rate that does not evolve with redshift, at least out to z~2.5. Galaxies follow this relation as their gas content evolves across the cosmic epochs. The projection of this 3D fundamental relation onto the stellar mass - star formation rate plane yields the Main Sequence relation and its evolution with redshift. We observe that the gas fraction of Main Sequence galaxies evolves differently depending on their stellar mass, in agreement with a so-called downsizing scenario.