Star Formation in Quasar Host Galaxies at Redshift 6: Millimeter Surveys and New Insights from ALMA

TL;DR

This study uses millimeter surveys and ALMA observations to investigate star formation and interstellar medium properties in z~6 quasar host galaxies, revealing high star formation rates and substantial molecular gas content.

Contribution

It provides new measurements of [C II] emission and molecular gas in z~6 quasars, offering insights into early galaxy evolution and quasar host galaxy properties.

Findings

Most z~6 quasars are bright in millimeter dust continuum.

Detected [C II] emission indicates active star formation.

Star formation rates are estimated between 600 and 2000 solar masses per year.

Abstract

We have been carrying out a systematic survey of the star formation and ISM properties in the host galaxies of z~6 quasars. Our 250 GHz observations, together with available data from the literature, yield a sample of 14 z~6 quasars that are bright in millimeter dust continuum emission with estimated FIR luminosities of a few 10^12 to 10^13 Lsun. Most of these millimeter-detected z~6 quasars have also been detected in molecular CO line emission, indicating molecular gas masses on order of 10^10 Msun. We have searched for [C II] 158 micron fine structure line emission toward four of the millimeter bright z~6 quasars with ALMA and all of them have been detected. All these results suggest massive star formation at rates of about 600 to 2000 Msun/yr over the central few kpc region of these quasar host galaxies.