类星体SDSS J2220+0109中特殊吸收线系统的发现与研究  

The Unusual Absorption Line Spectrum of Quasar SDSS J2220+0109

作　　者：纪拓[1,2] 周宏岩[1,2] 王挺贵[1] 王慧元[1] 

机构地区：[1]中国科学技术大学天体物理中心,合肥230026 [2]中国极地研究中心,上海200136

出　　处：《天文学报》2012年第5期357-368,共12页Acta Astronomica Sinica

基　　金：国家自然科学基金项目(10973013;1033007);国家海洋局极地研究专项(CHINARE2012-02-03);中央高校基本科研业务费专项资金(WK 2030220006)资助

摘　　要：斯隆数字巡天光谱数据中发现,类星体SDSS J2220+0109光谱中同时出现如下极为罕见的吸收线:氢巴尔末线Hα和Hβ,亚稳态He I* λλ3889、3189tt,CaⅡH、K,以及来自FeⅡ*能级的波数分别为7 955 cm^(-1)、13 474 cm^(-1)和13 673 cm^(-1)的众多吸收线.上述吸收线具有相似的速度结构,线宽达1 500 km·s^(-1),相对于发射线表现出蓝移.研究结果表明,这些吸收线很可能来自部分电离区,密度n_E≈10~6cm^(-3),柱密度N_(H I)≈10^(21) cm^(-2),Lyα共振散射对氢原子的激发起重要作用.SDSS J2220+0109斯隆r星等为16.56 mag,是探索活动星系核中特殊吸收线起源的理想实验室.将来的紫外光谱观测可以更加准确决定吸收气体的密度、柱密度、电离参数等物理性质;光学光谱监测有助于限定吸收线的产生机制.此外还发现,SDSS J2220+0109中的FeⅡ发射线显著区别于典型的窄线赛弗特Ⅰ型星系ⅠZw 1,很可能来自低密度气体,进一步研究有助于理解类星体中FeⅡ发射线的起源.We report the discovery of Balmer broad absorption lines （BALs） in the quasar SDSS J2220＋0109 and present a detailed analysis of the peculiar absorption line spectra. The absorption lines are detected in He I＊ multiplet at AA3189, 3889 arising from the metastable helium 23s level, and in Ha and H/3 from the excited hydrogen H I n = 2 level, which are rarely seen in quasar spectra. There are also many absorption lines arising from excited Fe II＊ levels 7955 cm-1, 13474 cm-1 and 13673 cm-1 in the wavelength range of 3100 - 3300A. Ca II H, K absorption line doublets are also clearly presented in its SDSS spectra. All absorption lines show a similar blueshifted velocity structure of Av -1500 - 0 km.s^-1 relative to the quasar systematic redshift determined from the emission lines. Detailed analysis suggests that the BALs should arise from partial ionized region with a column density of NH I ≈ 1021 cm^-2 for an electron density of ne ≈ 10^6 era^-3; and the hydrogen n = 2 level be populated via collisional excitation with Lyα pumping. In addition to its peculiar absorption features, SDSS J2220＋0109 also shows unusual Fe II emission lines very likely originated from the low density gas of ne ≈ 10^6 cm^-3, which is similar to that of the absorption gas.

关 键 词：类星体 吸收线 类星体 发射线 类星体 个别 SDSS J2220+0109 

分 类 号：P157[天文地球—天文学]