Radio-Quiet Quasars in the Direction of the Northern Hubble Deep Field

Abstract

We match quasars discovered in a multi-color survey centered on the northern Hubble Deep Field (HDF) with radio sources from an ultra-deep radio survey. Although 3 out of 12 quasars are detected at a level below 0.2 mJy at 1.4 GHz, all of the quasars in the search area are radio-quiet by the criterion L_r < 10^{25} h^{-1}_{50} W/Hz. We combine this information with other radio surveys of quasars so as to break the degeneracy between redshift and luminosity. In the redshift range 0.02 < z < 3.64, the radio-loud fraction increases with increasing optical luminosity, consistent with some degree of correlation between the non-thermal optical and radio emissions. More tentatively, for low luminosity quasars in the range -22.5 < M_B < -25, the radio-loud fraction decreases with increasing redshift. We can infer from this that the radio luminosity function evolves more slowly than the optical luminosity function. The mechanism that leads to strong radio emission in only a small fraction of quasars at any epoch is still unknown.

Accepted by the Astrophysical Journal; 16 pages total (includes 4 figures and 2 tables)

References in corpus (5)

• The Nature of Radio Emission from Distant Galaxies: The 1.4 GHz Observations
• A comparison of the optical properties of radio-loud and radio-quiet quasars
• The Asiago-ESO/RASS QSO Survey. I.The Catalog and the Local QSO Luminosity Function
• Quasars As Absorption Probes Of The Hubble Deep Field
• QSOs and Absorption Line Systems Surrounding the Hubble Deep Field

Cited by in corpus (3)

• The radio-luminosity - black hole mass correlation for quasars from the FIRST Bright Quasar Survey, and a ``unification scheme'' for radio-loud and radio-quiet quasars
• A Survey for Large Separation Lensed FIRST Quasars, II. Magnification Bias and Redshift Distribution
• Linking radio to infrared: a radio source count model