标题： 北方哈勃深场方向的无线电安静类星体 显示英文标题

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

摘要： 我们把在一个以北半球哈勃深场（HDF）为中心的多色巡天中发现的类星体与来自一项超深射电巡天的射电源相匹配。尽管在12个类星体中有3个在1.4 GHz频率下被检测到的水平低于0.2 mJy，但按照L_r < 10^{25} h^{-1}_{50} W/Hz的标准，搜索区域内的所有类星体都是宁静的射电源。我们将这些信息与其他类星体的射电巡天结果结合起来，以便解决红移和光度之间的退化问题。在红移范围0.02 < z < 3.64内，随着光学光度的增加，射电明亮类星体的比例也随之增加，这与非热光学辐射和射电辐射之间一定程度的相关性一致。更谨慎地说，在光度范围-22.5 < M_B < -25内的低光度类星体中，射电明亮类星体的比例随着红移的增加而减少。由此我们可以推断出，射电光度函数的演化速度比光学光度函数慢。导致只有小部分类星体在任一时期产生强射电辐射的机制仍然是未知的。 显示英文摘要

摘要： 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.