Dense molecular gas in quasar host galaxies: A search for HCN emission from BR B1202-0725 at z = 4.695

Abstract

We report on the results of a search using the VLA for redshifted HCN(1-0) emission from the host galaxy of BR B1202-0725, an optically luminous quasar at z = 4.695. The host galaxy emits strongly in the rest-frame far-infrared, and shows characteristics very similar to those of more local ultraluminous infrared galaxies, in which a significant fraction of the far-infrared emission is powered by star formation. We find a 3σ upper limit to the HCN(1-0) emission of 4.9 × 1010 K km s-1 pc2, assuming a Δ cosmology. This limit is consistent with correlations derived from measurements of HCN, CO, and far-infrared emission for a sample of more local galaxies including starbursts.