A 1.2 mm MAMBO/IRAM-30 m study of dust emission from optically luminous z ≈ 2 quasars

We report 250 GHz (1.2 mm) observations of redshift 1.8 < z < 2.8 optically luminous (M-B < -27.0), radio quiet quasars using the Max-Planck Millimeter Bolometer (MAMBO) array at the IRAM 30-metre telescope. Nine quasars were detected and for 26 quasars 3 sigma flux density limits in the range 1.8 to 4 mJy were obtained. Adopting a typical dust temperature of 45 K, the millimeter emission implies far-infrared luminosities of order 10(13) L., and dust masses of similar to 10(8) M.. Applying a statistical survival analysis to our total sample of 43 detected and 95 undetected quasars at z approximate to 2 and z greater than or similar to 4, we find that there is no apparent difference in the far-infrared (FIR) luminosities, hence the star formation rates, of QSOs at z approximate to 2 and at 3.6 < z < 5. This differs from radio galaxies, for which the FIR luminosity was found to increase with redshift (Archibald et al. 2001). We furthermore find that there is no strong correlation between the far-infrared and optical luminosities, confirming previous results obtained on smaller samples.