Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey
Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey
复制标题
DOI：
10.3847/1538-4357/aaa9b6
复制
发表时间：
2017-06
期刊：
影响因子：
--
通讯作者：
Nick Rumbaugh;Yue Shen;E. Morganson;Xin Liu;M. Banerji;Richard G. McMahon;Filipe Abdalla;
中科院分区：
文献类型：
--
作者：
Nick Rumbaugh;Yue Shen;E. Morganson;Xin Liu;M. Banerji;Richard G. McMahon;Filipe Abdalla;
我们在重叠的斯隆数字巡天和3年暗能量巡天成像中对长期极端变率类星体(EVQ)进行了系统的搜索，这些成像提供了跨越15年以上的光曲线。我们发现了∼1000EVQ，在这段时间内g带幅度的最大变化超过1 MAG，约占所有搜索到的类星体的10%。这些EVQ具有LBOL∼1045-1047erg S−1和L/LEdd∼0.01-1。考虑到选择效应，我们估计在基线为∼15年的所有类星体中，∼的本征EVQ比例为30%-50%。我们对EVQ进行了详细的多波长、光谱和变异性分析，并将它们与它们的父类星体样本进行了比较。我们发现EVQ与红移和光学光度匹配的类星体的对照样本不同：(1)它们的UV宽发射线具有更大的等效宽度；(2)它们的爱丁顿比系统地较低；(3)它们在所有时间尺度上都更加可变。EVQs类星体性质的内在差异表明，与吸积相关的内部过程是观测到的极端长期变率的主要驱动因素。然而，尽管它们的性质不同，但EVQ似乎处于类星体性质的连续分布的尾部，而不是作为一个独特的群体脱颖而出。我们推测，EVQs是以相对较低的速率吸积的正常类星体，其中吸积流更有可能经历不稳定，这种不稳定在多年时间尺度上以几个因素驱动通量的变化。
We perform a systematic search for long-term extreme variability quasars (EVQs) in the overlapping Sloan Digital Sky Survey and 3 Year Dark Energy Survey imaging, which provide light curves spanning more than 15 years. We identified ∼1000 EVQs with a maximum change in g-band magnitude of more than 1 mag over this period, about 10% of all quasars searched. The EVQs have Lbol ∼ 1045–1047 erg s−1 and L/LEdd ∼ 0.01–1. Accounting for selection effects, we estimate an intrinsic EVQ fraction of ∼30%–50% among all quasars over a baseline of ∼15 yr. We performed detailed multi-wavelength, spectral, and variability analyses for the EVQs and compared them to their parent quasar sample. We found that EVQs are distinct from a control sample of quasars matched in redshift and optical luminosity: (1) their UV broad emission lines have larger equivalent widths; (2) their Eddington ratios are systematically lower; and (3) they are more variable on all timescales. The intrinsic difference in quasar properties for EVQs suggests that internal processes associated with accretion are the main driver for the observed extreme long-term variability. However, despite their different properties, EVQs seem to be in the tail of a continuous distribution of quasar properties, rather than standing out as a distinct population. We speculate that EVQs are normal quasars accreting at relatively low rates, where the accretion flow is more likely to experience instabilities that drive the changes in flux by a factor of a few on multi-year timescales.