THE COSMIC EVOLUTION OF FERMI BL LACERTAE OBJECTS
THE COSMIC EVOLUTION OF FERMI BL LACERTAE OBJECTS
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DOI：
10.1088/0004-637x/780/1/73
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发表时间：
2014-01-01
影响因子：
4.9
通讯作者：
Schady, P.
中科院分区：
文献类型：
--
作者：
Ajello, M.;Romani, R. W.;Schady, P.
费米提供了迄今为止最大的伽马射线选择耀变体样本。在这项工作中，我们使用了一个统一的选择211 BL Lacertae（BL紫胶）费米在其第一年的操作中检测到的对象。在我们的样本中，我们获得了211个BL Lac天体中的206个的红移约束，使其成为文献中最大和最完整的BL Lac天体样本。我们使用这个样本来确定BL Lac天体的光度函数及其随宇宙时间的演化。我们发现，对于大多数BL Lac类的演变是积极的，与空间密度峰值在适度的红移（z近似为1.2）。低光度，高同步加速器峰值（HSP）BL Lac天体是一个例外，显示出强烈的负演化，当z小于或接近0.5时，数密度增加。由于这种上升对应于平谱射电类星体（FSRQ）密度的下降，一种可能的解释是，这些HSP代表了早期合并驱动的富气阶段的吸积饥饿的终态。我们还发现，已知的BL Lac光度和光子光谱指数之间的相关性仍然存在校正后的大量观测选择效应与所谓的“耀变体序列的影响。“最后，通过估计对光度函数的光束修正，我们发现BL Lac天体的平均洛伦兹因子为伽马= 6.1（-0.8）（+1.1），并且大多数都在喷流轴的10度范围内。
Fermi has provided the largest sample of gamma-ray-selected blazars to date. In this work we use a uniformly selected set of 211 BL Lacertae (BL Lac) objects detected by Fermi during its first year of operation. We obtained redshift constraints for 206 out of the 211 BL Lac objects in our sample, making it the largest and most complete sample of BL Lac objects available in the literature. We use this sample to determine the luminosity function of BL Lac objects and its evolution with cosmic time. We find that for most BL Lac classes the evolution is positive, with a space density peaking at modest redshift (z approximate to 1.2). Low-luminosity, high-synchrotron-peaked (HSP) BL Lac objects are an exception, showing strong negative evolution, with number density increasing for z less than or similar to 0.5. Since this rise corresponds to a drop-off in the density of flat-spectrum radio quasars (FSRQs), a possible interpretation is that these HSPs represent an accretion-starved end state of an earlier merger-driven gas-rich phase. We additionally find that the known BL Lac correlation between luminosity and photon spectral index persists after correction for the substantial observational selection effects with implications for the so-called "blazar sequence." Finally, by estimating the beaming corrections to the luminosity function, we find that BL Lac objects have an average Lorentz factor of gamma = 6.1(-0.8)(+1.1), and that most are seen within 10 degrees of the jet axis.