Rest-frame optical continua of L∼L*, z > 3 quasars: probing the faint end of the high-z quasar luminosity function
Rest-frame optical continua of L∼L*, z > 3 quasars: probing the faint end of the high-z quasar luminosity function
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L〜L*，z > 3个类星体的静止框架光学连续体：探测高z类星体光度函数的微弱末端
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发表时间：
2003
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通讯作者：
O. Kuhn
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作者：
O. Kuhn
本文介绍了20个射电响亮的z>；3类星体的近红外(IR)光度测量，其中16个是射电选择类星体。这些数据采样了静止框架的光学/紫外线(UV)连续体，这通常被解释为来自吸积盘的发射。在之前的研究中，我们比较了15个光学明亮(V3)类星体和27个低红移(z∼0.1)类星体的其余标架光学/UV连续谱形状，这些类星体在演化光度(即光度从特征光度的1到7倍的范围内变化，L∗，其中L∗∼(1+z)∼3)与高红移样本相匹配，以寻找中央引擎中的演化迹象。我们发现在z∼0.1时和z>；3处的连续体形状相似，但比值·m/M没有明显变化，其中·m是相对于爱丁顿速率的吸积率，M是黑洞质量。这项研究将我们早先的高红移样本扩展到低光度，远离极端物体，朝着与低红移样本重叠的光度方向发展。与较亮的z>；3样品相比，这个较暗的样品的静止框架光学/UV连续谱形状的分布更宽，向红色延伸得更远。这个较暗的样本中的三个类星体，两个是射电选择的，一个是光学选择的，具有光学连续谱斜率α<；−1(Fν∼να)。光学选择的LBQS 0056+0125似乎被视线沿线或宿主星系中的尘埃染红，而射电选择的PKS 2215+02和TXS 2358+189可能是由于相对较强的同步加速器分量对静止的光学框架的贡献而产生的红色连续体。这些天体可能代表着通往极红高红移类星体群体的桥梁，正在进行或未来的近红外、光学和深X射线探测将对这些类星体敏感。
Near-infrared (IR) photometry for 20 radio-loud z > 3 quasars, 16 of which are radio-selected, are presented. These data sample the rest-frame optical/ultraviolet (UV) continuum, which is commonly interpreted as emission from an accretion disc. In a previous study, we compared the rest-frame optical/UV continuum shapes of 15 optically bright (V 3 quasars with those of 27 low-redshift (z ∼ 0.1) quasars that were matched to the high-redshift sample in evolved luminosity (i.e. having luminosities ranging from 1 to 7 times the characteristic luminosity, L ∗ , where L ∗ ∼ (1 + z) ∼3 ) to look for signs of evolution in the central engines. We found the continuum shapes at z ∼ 0.1 and z > 3 similar, consistent with no significant change in the ratio ˙ m/M, where ˙ m is the accretion rate with respect to the Eddington rate and M is the black-hole mass. This study expands our earlier high-redshift sample to lower luminosity, away from extreme objects and towards a luminosity overlap with lower-redshift samples. The distribution of rest-frame optical/UV continuum shapes for this fainter sample is broader, extending further to the red than that of the brighter z > 3 sample. Three quasars from this fainter sample, two radio-selected and one optically selected, have optical continuum slopes α< − 1( Fν ∼ ν α ). The optically selected one, LBQS 0056+0125, appears to be reddened by dust along the line of sight or in the host galaxy, whereas the radio-selected ones, PKS 2215+02 and TXS 2358+189, could derive their red continua from the contribution of a relatively strong synchrotron component to the rest-frame optical. These objects may represent a bridge to a population of very red high-redshift quasars to which ongoing or future near-IR, optical and deep X-ray surveys will be sensitive.