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arXiv 2009.07945astro-ph.HE
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用Fermi/LAT寻找高红移耀变体

Search for high-redshift blazars with Fermi/LAT

M. Kreter, A. Gokus, F. Krauß, M. Kadler, R. Ojha, S. Buson, J. Wilms, M. Böttcher

摘要:

高$z$耀变体(z $\geq 2.5$)是宇宙中最强大的一类持久性$γ$射线源.这些天体拥有最高的喷流功率和光度,黑洞质量通常超过$10^9$太阳质量。此外,高$z$耀变体是重要的宇宙学探测器,也是耀变体演化模型的测试对象。由于它们的距离很远,它们的高能发射通常在GeV范围以下达到峰值,这使得它们很难用费米/LAT进行研究。因此,只有非常明亮的物体是可探测的,到目前为止,只有少量的高Z耀变体已被费米/LAT探测到。在这项工作中,我们研究了176个射电和光学探测到的耀变体样本的月度分组长期$γ$射线发射,这些耀变体在3FGL星表中没有被报道为已知的$γ$射线源。为了解释假阳性检测,我们计算了大量空白天空位置样本的每月费米/LAT光变曲线,并推导出我们在各种测试统计(TS)水平上预期的随机波动数量。对于一个给定的blazar,预计至少在一个月内探测到TS > 9的$\sim 15\%$的时间。虽然这个速率太高,不足以确保探测到单个的源,但我们的样本中有一半显示了这种单月$γ$射线活动,表明在z=5.2的距离上存在着高能耀变体。多个TS > 9的月探测不太可能偶然发生,我们已经以这种方式探测到了几个单独的新来源,包括最遥远的$γ$射线耀变体BZQ J1430+4204(z = 4.72)。最后,两个新的$γ$射线耀变体的红移为z = 3.63和z = 3.11明确地检测到通过非常显着的(TS > 25)耀斑在个人的月度时间箱。

英文摘要:

High-$z$ blazars (z $\geq 2.5$) are the most powerful class of persistent $γ$-ray sources in the Universe. These objects possess the highest jet powers and luminosities and have black hole masses often in excess of $10^9$ solar masses. In addition, high-$z$ blazars are important cosmological probes and serve as test objects for blazar evolution models. Due to their large distance, their high-energy emission typically peaks below the GeV range, which makes them difficult to study with Fermi/LAT. Therefore, only the very brightest objects are detectable and, to date, only a small number of high-z blazars have been detected with Fermi/LAT. In this work, we studied the monthly binned long-term $γ$-ray emission of a sample of 176 radio and optically detected blazars that have not been reported as known $γ$-ray sources in the 3FGL catalog. In order to account for false-positive detections, we calculated monthly Fermi/LAT light curves for a large sample of blank sky positions and derived the number of random fluctuations that we expect at various test statistic (TS) levels. For a given blazar, a detection of TS > 9 in at least one month is expected $\sim 15\%$ of the time. Although this rate is too high to secure detection of an individual source, half of our sample shows such single-month $γ$-ray activity, indicating a population of high-energy blazars at distances of up to z=5.2. Multiple TS > 9 monthly detections are unlikely to happen by chance, and we have detected several individual new sources in this way, including the most distant $γ$-ray blazar, BZQ J1430+4204 (z = 4.72). Finally, two new $γ$-ray blazars at redshifts of z = 3.63 and z = 3.11 are unambiguously detected via very significant (TS > 25) flares in individual monthly time bins.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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