A high-energy view of the galaxy-scale metal gas
by Johannes Buchner (Universidad Catolica, Chile)
Abstract. At the peak of star formation (z=0.5-3), an important yet
hard-to-constrain measurable is the metal gas content of galaxies, a
side-product of the evolution of massive stars, and the origin of rocky
planets like the earth. At the same time, high-energy source (AGN, GRB) emission is absorbed by
this gas along the observers line-of-sight. Therefore it could be
interesting to indirectly do galaxy tomography with these column densities.
We performed a survey of afterglow obscuration of all Swift-detected
gamma-ray bursts (GRB), studying selection biases and advancing analysis
methodology. While we find little redshift evolution, a clear correlation of host
stellar mass and metal column density is revealed. A simple geometrical
model explains the width and shape of the column density distribution
and the trend with galaxy mass correlation. Our results implicate the
host's galaxy-scale metal gas as the dominant obscurer.
From a galaxy evolution perspective, our study places new independent
constraints on the metal gas mass inside galaxies at z= 0.5 - 4. We compare
these with modern cosmological simulations (Illustris and EAGLE) and
discuss implications for the obscuration of other sources inside high
redshift galaxies, such as active galactic nuclei (AGN).