星系群中活动星系核的比例研究

Investigation on Active Galactic Nucleus Fraction in Galaxy Groups

相对于大量X射线辐射显著而无光学发射线的活动星系核(AGN),已被光谱证认了的X射线选AGN可能尚处于黑洞显著增长的高吸积率演化阶段,因而具有明显的光学发射线特征.利用COSMOS(Cosmological Evolution Survey)天区深场多波段测光和光谱数据,在红移范围为0.1<z<1.0的星系群成员星系样本中寻找具有光学发射线特征的X射线选AGN.研究发现,星系群中的绝大多数这类AGN(约96%)是窄发射线AGN,星系群中AGN比例普遍低于1%,且随着红移有微弱的上升趋势.

Compared with numerous X-ray-dominant active galactic nuclei （AGNs） without emission-line signatures in their optical spectra, the spectroscopically identified, X-ray selected AGNs are likely in the high-accretion evolutional phase of black hole growth, thus they have obvious emission-line signatures. Using the multiwavelength photometric and spectral data in the COSMOS （Cosmological Evolution Survey） deep field, we search the spectroscopically confirmed, X-ray selected AGNs in the samples of group member galaxies within a redshift range of 0.1 〈 z 〈 1.0. It is shown that majority （-96%） of AGNs in groups are narrow-line AGNs. Though overall AGN fraction in groups is likely to be less than 1%, a slight raising tendency with redshift is found in AGN fractions in groups.