通过SDSS测光红移的宇宙邻域关联法估算VHE及候选VHE BL Lac天体的距离
Cosmic-neighbor-associated distances to VHE and candidate VHE BL Lacs via SDSS photometric redshifts
- Norwegian University of Science and Technology（挪威科技大学）
- University of Turku（图尔库大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文提出利用SDSS测光红移和宇宙邻域关联法估计BL Lac天体距离，精度达Δz~0.02-0.04，并为多个VHE源提供可能红移，以改进耀变体距离测量。
AI中文摘要：
BL Lac天体的距离难以估计，因为其光学光谱很少显示出可识别的发射线或吸收线。我们提出了一种方法，通过将BL Lac天体与其在光学场中识别出的宇宙邻域（宇宙网中的局部过密区域）相关联来约束其距离。这些邻域中星系的距离利用斯隆数字巡天（SDSS）的测光红移进行估计。利用先前通过多目标光谱建立的宇宙邻域关联以及具有光谱测量红移的BL Lac天体作为对照样本，我们发现关联邻域的红移可以以$\Delta z \sim 0.02-0.04$的精度恢复。当场中存在多个候选邻域时，我们使用中心位置准则对候选关联进行排序。在50%的情况下，BL Lac天体与正确的邻域相关联。我们为没有可靠红移测量的BL Lac天体提供了距离估计，重点关注在甚高能（VHE；$E>100$ GeV）下探测到的源以及候选VHE辐射体。结合 intervening吸收系统、宿主星系成像、$\gamma$-射线约束以及我们的SDSS群关联方法，我们为TXS 0141$+$268（$z\sim0.93-0.95$）、PKS 0735$+$178（$z=0.64$）、3FHL J0905.5$+$1357（$z=0.644$）、B2 0912$+$29（$z=0.53$）、3FHL J1120.8$+$4212（$z=0.363$）、BZB J1243$+$3627（$z=0.485$）、3FHL J1253.1$+$5300（$z=0.664$）和RX J2156.0$+$1818（$z=0.635$）提出了可能的红移。最后，我们讨论了即将开展的窄带测光红移巡天如何通过群关联技术改进耀变体的距离估计。
英文摘要：
BL Lac objects have distances that are difficult to estimate because their optical spectra rarely show identifiable emission or absorption lines. We present a method to constrain BL Lac distances by associating them with their cosmic neighborhoods (local overdensities in the cosmic web) identified in optical fields. Distances to galaxies in these neighborhoods are estimated using the Sloan Digital Sky Survey (SDSS) photometric redshifts. Using cosmic-neighborhood associations previously established from multi-object spectroscopy and BL Lacs with spectroscopically measured redshifts as control samples, we find that the redshifts of the associated neighborhoods can be recovered with an accuracy of $Δz \sim 0.02-0.04$. When multiple candidate neighborhoods are present in the field, we rank the candidate associations using a central-location criterion. In 50% of cases, the BL Lac is associated with the correct neighborhood. We provide distance estimates for BL Lac objects without secure redshift measurements, focusing on sources detected at very high energies (VHE; $E>100$,GeV) and on candidate VHE emitters. Combining intervening absorption systems, host-galaxy imaging, $γ$-ray constraints, and our SDSS group-association method, we propose likely redshifts for TXS 0141$+$268 ($z\sim0.93-0.95$), PKS 0735$+$178 ($z=0.64$), 3FHL J0905.5$+$1357 ($z=0.644$), B2 0912$+$29 ($z = 0.53$), 3FHL J1120.8$+$4212 ($z=0.363$), BZB J1243$+$3627 ($z=0.485$), 3FHL J1253.1$+$5300 ($z=0.664$), and RX J2156.0$+$1818 ($z=0.635$). Finally, we discuss how forthcoming narrow-band photometric-redshift surveys can improve blazar distance estimates via group-association techniques.
