The Canada-France High-zQuasar Survey: 1.2 mm observations

A Omont,A Beelen,P Delorme,G Orellana,C J Willott,J Bergeron

doi:10.1051/0004-6361/201221006

Abstract

We report 250 GHz (1.2 mm) observations of a sample of 20 QSOs at redshifts 5.8<z<6.5 from the the Canada-France High-z Quasar Survey (CFHQS), using the Max-Planck Millimeter Bolometer (MAMBO) array at the IRAM 30-metre telescope. A rms sensitivity <~ 0.6 mJy was achieved for 65% of the sample, and <~ 1.0 mJy for 90%. Only one QSO, CFHQS J142952+544717, was robustly detected with S_250GHz = 3.46 +/-0.52 mJy. This indicates that one of the most powerful known starbursts at z~6 is associated with this radio loud QSO. On average, the other CFHQS QSOs, which have a mean optical magnitude fainter than previously studied SDSS samples of z~6 QSOs, have a mean 1.2 mm flux density <S_250GHz> = 0.41 +/-0.14 mJy; such a 2.9-sigma average detection is hardly meaningful. It would correspond to <L_FIR> ~ 0.94+/-0.32 10^12 Lo, and an average star formation rate of a few 100's Mo/yr, depending on the IMF and a possible AGN contribution to <L_FIR>. This is consistent with previous findings of Wang et al. (2011) on the far-infrared emission of z~6 QSOs and extends them toward optically fainter sources.

Highlights

The highest-redshift quasars which are known at z 6 are fascinating objects that provide crucial clues about the growth of supermassive black holes (SMBH), their host galaxies, and their environment toward the end of the reionization epoch when the Universe was less than 1 Gyr old
The exceptionally strong 1.2 mm flux density that we found for Canada-France High-z Quasar Survey (CFHQS) J1429+5447 led to the selection of this source to search for CO(2−1) emission (Wang et al 2011b)
If the FIR emission is powered by a dusty starburst, there is a direct relation between star formation rate (SFR) and LFIR

Summary

Introduction

The highest-redshift quasars which are known at z 6 are fascinating objects that provide crucial clues about the growth of supermassive black holes (SMBH), their host galaxies, and their environment toward the end of the reionization epoch when the Universe was less than 1 Gyr old. Coming from deeper optical surveys, the CFHQS sample contains quasars optically much fainter than both the main SDSS sample and the SDSS deep southern survey The purpose of this Note is to publish the results of the 1.2 mm survey of the 20 z ∼ 6 CFHQS quasars that we performed to extend the existing studies of FIR properties of quasars at similar redshifts to optically fainter sources. The exceptionally strong 1.2 mm flux density that we found for CFHQS J1429+5447 led to the selection of this source to search for CO(2−1) emission (Wang et al 2011b) Together with those of Wang et al (2011a), our results provide a useful background for the much deeper studies of submillimeter properties of optically faint z ∼ 6 quasars that we have already begun with The Atacama Large Millimeter/submillimeter Array (ALMA, Willott et al 2013).

Observations

Estimates of LFIR and Mdust

Average FIR luminosities

Findings

Discussion and conclusions