(Proposal ID) S13B-009

(PI) Nagao, Tohru

(Proposal Title)
Revealing the Nature of Dense Gas Clouds in High-z Quasar Host Galaxies

(Abstract)
Millimeter observations of molecular lines in quasar hosts show the presence 
of dense gas clouds, which are the key for the co-evolution of galaxies and 
supermassive black holes (SMBHs). However, those molecular lines are seen only 
in some AGN hosts and thus our understandings of dense clouds in molecular-
detected AGNs may not be true for the whole AGN population. In addition, 
physical and chemical properties of those clouds are hard to be assessed by 
the molecular lines. Here we propose a new approach to study the dense clouds 
in quasar hosts, through NLR lines seen in rest-frame optical spectra of 
quasars. Our previous MOIRCS run for a luminous type-1 quasar at z ~ 3 found a 
strong [Ne iii] but no [O ii] emission, suggesting the presence of abundant 
dense gas clouds in the host galaxy. Here we propose a systematic study of NLR 
flux ratios in luminous quasars at z ~ 3 to examine whether or not there are 
abundant dense gas clouds in quasar host galaxies. We can give constraints on 
physical properties of those clouds by combining the [Ne iii], [O ii], 
[O iii]lambda4363, and [O iii]lambda5007. By comparing the dense gas properties
 with quasar properties such as the AGN luminosity and Eddington ratio, we 
will understand the role of the dense clouds for the AGN activity and 
SMBH growth.