Radio observations of the cool gas, dust, and star formation in the first galaxies

TL;DR

This paper reviews radio and submillimeter observations of z~6 quasar host galaxies, revealing active star formation, large molecular gas reservoirs, and early galaxy-black hole co-evolution within the first billion years.

Contribution

It provides new insights into the properties of early galaxies and their central black holes through detailed radio and submm observations, highlighting their rapid growth and deviation from local relations.

Findings

Active star formation in ~30% of hosts (~10^3 M_sun/year)

Molecular gas masses ~10^10 M_sun

Black holes are ~15 times more massive than expected from local relations

Abstract

We summarize cm through submm observations of the host galaxies of z ~ 6 quasars. These observations reveal the cool molecular gas (the fuel for star formation), the warm dust (heated by star formation), the fine structure line emission (tracing the CNM and PDRs), and the synchrotron emission. Our results imply active star formation in ~ 30% of the host galaxies, with star formation rates ~ 10^3 M_sun/year, and molecular gas masses ~ 10^10 M_sun. Imaging of the [CII] emission from the most distant quasar reveals a 'maximal starburst disk' on a scale ~ 1.5 kpc. Gas dynamical studies suggest a departure of these galaxies from the low-z M_{BH} -- M_{bulge} relation, with the black holes being, on average, 15 times more massive than expected. Overall, we are witnessing the co-eval formation of massive galaxies and supermassive black holes within 1 Gyr of the Big Bang.