Research Note

The Canada-France High-z Quasar Survey: 1.2 mm observations

¹ UPMC Univ Paris 06, UMR 7095, Institut d’Astrophysique de Paris, 75014 Paris, France
e-mail: omont@iap.fr
² CNRS, UMR 7095, Institut d’Astrophysique de Paris, 75014 Paris, France
³ Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Rd, Victoria, BC V9E 2E7, Canada
⁴ Univ Paris-Sud and CNRS, Institut d’Astrophysique Spatiale, UMR 8617, 91405 Orsay, France
⁵ Astronomy DepartmentUniversidad de Concepción, Casilla 160- C Concepción, Chile
⁶ UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041 Grenoble, France

Received: 25 December 2012
Accepted: 27 January 2013

Abstract

We report 250 GHz (1.2 mm) observations of a sample of 20 quasars at redshifts 5.8 < z < 6.5 from the Canada-France High-z Quasar Survey (CFHQS), using the Max-Planck-Millimeter-Bolometer (MAMBO) array at the 30-metre telescope of the Institut de Radioastronomie Millmétrique (IRAM). An rms sensitivity of ≲0.6 mJy was achieved for 65% of the sample, and of ≲1.0 mJy for 90%. Only one quasar, CFHQS J142952+544717, was robustly detected with S_{250   GHz} = 3.46 ± 0.52 mJy. This indicates that one of the most powerful known starbursts at z ~ 6 is associated with this radio-loud quasar. On average, the other CFHQS quasars, which have a mean optical magnitude fainter than the previously studied samples of z ~ 6 quasars of the Sloan Digital Sky Survey (SDSS), have a mean 1.2 mm flux density ⟨ S_{250   GHz} ⟩  = 0.41 ± 0.14 mJy; this average detection with a signal-to-noise (S/N) ratio of 2.9 is hardly meaningful. It would correspond to ⟨ L_FIR ⟩  ≈ 0.94 ± 0.32 × 10¹²   L_⊙, and an average star formation rate of a few 100 M_⊙/yr, depending on the stellar initial mass function (IMF) and a possible contribution of an active galactic nucleus (AGN) to ⟨ L_FIR ⟩. This is consistent with previous findings of Wang et al. on the far-infrared emission of z ~ 6 quasars and extends their results toward optically fainter sources.