Candidate Periodically Variable Quasars from the Dark Energy Survey and the Sloan Digital Sky Survey
Candidate Periodically Variable Quasars from the Dark Energy Survey and the Sloan Digital Sky Survey
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来自暗能量巡天和斯隆数字巡天的候选周期变类星体
DOI：
10.1093/mnras/staa2957
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发表时间：
2020
影响因子：
4.8
通讯作者：
Abbott, Tim M
中科院分区：
文献类型：
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作者：
Chen, Yu-Ching;Liu, Xin;Liao, Wei-Ting;Holgado, A Miguel;Guo, Hengxiao;Gruendl, Robert A;Morganson, Eric;Shen, Yue;Zhang, Kaiwen;Abbott, Tim M
周期性变化的类星体被认为是紧密的超大质量双黑洞。我们提出了一个系统的搜索周期性光变曲线在625光谱确认类星体的中位红移为1.8在4.6 deg 2的暗能量调查超新星（DES-SN）领域和斯隆数字巡天条纹82（SDSS-S82）的重叠区域。我们的样品具有独特的20年长的多色（griz）光变曲线，通过将DES-SN Y 6观测与SDSS-S82存档数据相结合实现。深度成像使我们能够第一次在高红移下寻找由质量较小的黑洞（质量为108.5M）驱动的不太明亮的类星体（低于23.5等）中的周期性光变曲线。我们发现了5个具有显著周期性（在至少两个波段中具有> 99.74%的单频显著性，全局p值为1.7 × 10−4-3 × 10− 3，考虑到了“别处看”效应）的候选天体，观测周期为1.3 -5年（即在静止坐标系中为1-2年），观测跨越了1.4 -6个周期。如果所有五个候选者都是周期性变化的类星体，这意味着每平方度的类星体探测率为%。我们的检测率是4-80倍，比以前的搜索发现，使用更浅的调查更大的地区。这种差异可能是由探测的类星体数量和调查数据质量的差异造成的。我们讨论了未来直接探测低频引力波的影响。持续的光度监测将进一步评估这些候选周期类星体的稳健性和特征，以确定它们的物理起源。
Periodically variable quasars have been suggested as close binary supermassive black holes. We present a systematic search for periodic light curves in 625 spectroscopically confirmed quasars with a median redshift of 1.8 in a 4.6 deg2overlapping region of the Dark Energy Survey Supernova (DES-SN) fields and the Sloan Digital Sky Survey Stripe 82 (SDSS-S82). Our sample has a unique 20-yr long multicolour (griz) light curve enabled by combining DES-SN Y6 observations with archival SDSS-S82 data. The deep imaging allows us to search for periodic light curves in less luminous quasars (down tor∼23.5 mag) powered by less massive black holes (with masses ≳ 108.5M⊙) at high redshift for the first time. We find five candidates with significant (at >99.74 per cent single-frequency significance in at least two bands with a global p-value of ∼7 × 10−4–3 × 10−3accounting for the look-elsewhere effect) periodicity with observed periods of ∼3–5 yr (i.e. 1–2 yr in rest frame) having ∼4–6 cycles spanned by the observations. If all five candidates are periodically variable quasars, this translates into a detection rate ofper cent orquasar per deg2. Our detection rate is 4–80 times larger than those found by previous searches using shallower surveys over larger areas. This discrepancy is likely caused by differences in the quasar populations probed and the survey data qualities. We discuss implications on the future direct detection of low-frequency gravitational waves. Continued photometric monitoring will further assess the robustness and characteristics of these candidate periodic quasars to determine their physical origins.