Optical spectroscopy of blazars for the Cherenkov Telescope Array – II
Optical spectroscopy of blazars for the Cherenkov Telescope Array – II
复制标题
切伦科夫望远镜阵列的耀变体光谱 – II
DOI：
10.1093/mnras/stac3167
复制
发表时间：
2022
影响因子：
4.8
通讯作者：
Becerra González, J.
中科院分区：
文献类型：
--
作者：
Kasai, E.;Goldoni, P.;Pita, S.;Williams, D. A.;Max-Moerbeck, W.;Hervet, O.;Cotter, G.;Backes, M.;Boisson, C.;Becerra González, J.
迄今为止，大气层切伦科夫成像望远镜探测到的250多个甚高能伽马射线源中，活动星系核约占35%。除了四个邻近的射电星系和两个未知类型的活动星系核外，所有已知的VHE活动星系核都是耀变体。伽玛射线耀变体的宇宙学红移知识是研究其内在发射特性的关键，因为伽玛射线与河外背景光（EBL）之间的相互作用导致光谱软化。因此，红移的测定工作是至关重要的，间接地把严格的限制在EBL密度，并研究耀变体人口的演变跨越宇宙时间。由于耀变体中强大的相对论喷流，其宿主星系的光谱特征大多被掩盖，需要专门的高信噪比（S/N）光谱观测。欧洲南方天文台、新技术望远镜、凯克二号望远镜、沙恩3米望远镜和南部非洲大望远镜对33个伽马射线耀变体光学对应物进行了深中高分辨率光谱学研究。从样本中，来自25个对象的光谱显示光谱特征或无特征，具有高S/N。其他八个天体的光谱质量很低，没有特征。我们系统地搜索吸收和发射功能，并估计，如果可能的话，在测量的总流量的分数主机星系流量。我们的测量得到了14个确定的光谱红移，范围从0.0838到0.8125，一个暂定的红移，和两个下限：一个在atz，另一个atz> 0.629。
Active galactic nuclei (AGNs) make up about 35 per cent of the more than 250 sources detected in very high-energy (VHE) gamma rays to date with the imaging atmospheric Cherenkov telescopes. Apart from four nearby radio galaxies and two AGNs of unknown type, all known VHE AGNs are blazars. Knowledge of the cosmological redshift of gamma-ray blazars is key to enabling the study of their intrinsic emission properties, as the interaction between gamma rays and the extragalactic background light (EBL) results in a spectral softening. Therefore, the redshift determination exercise is crucial to indirectly placing tight constraints on the EBL density, and to studying blazar population evolution across cosmic time. Due to the powerful relativistic jets in blazars, most of their host galaxies’ spectral features are outshined, and dedicated high signal-to-noise (S/N) spectroscopic observations are required. Deep medium- to high-resolution spectroscopy of 33 gamma-ray blazar optical counterparts was performed with the European Southern Observatory, New Technology Telescope, Keck II telescope, Shane 3-metre telescope, and the Southern African Large Telescope. From the sample, spectra from 25 objects display spectral features or are featureless and have high S/N. The other eight objects have low-quality featureless spectra. We systematically searched for absorption and emission features and estimated, when possible, the fractional host galaxy flux in the measured total flux. Our measurements yielded 14 firm spectroscopic redshifts, ranging from 0.0838 to 0.8125, one tentative redshift, and two lower limits: one atand the other atz> 0.629.