Narrow absorption lines with two observations from the Sloan Digital Sky Survey

Abstract

We assemble 3524 quasars from Sloan Digital Sky Survey (SDSS) with repeated observations to search for variations of narrow C IVλλ1548, 1551 and Mg IIλλ2796, 2803 absorption doublets in spectral regions shortward of 7000Å at the observed frame, which corresponds to time-scales of about 150 ∼ 2643 days at quasar rest frame. In these quasar spectra, we detect 3580 C IV absorption systems with z abs = 1.5188 ∼ 3.5212, and 1809 Mg II absorption systems with z abs = 0.3948 ∼ 1.7167. In term of the absorber velocity (β) distribution at quasar rest frame, we find a substantial number of C IV absorbers with β < 0.06, which might be connected to the absorptions of quasar outflows. The outflow absorptions peak at υ ≈ 2000 km s −1 and drop rapidly below the peak value. Among 3580 C IV absorption systems, 52 systems (∼ 1.5%) show obvious variations in equivalent widths at the absorber rest frame (W r ): 16 enhanced, 16 emerged, 12 weaken, and 8 disappeared systems, respectively. We find that changes in W r λ1548 are neither related to time-scales of the two SDSS observations, nor to absorber velocities at the quasar rest frame. Variable absorptions in low-ionization species are important to constraint the physical conditions of absorbing gas. There are two variable Mg II absorption systems measured from SDSS spectra detected by Hacker et al. However, in our Mg II absorption sample, we find that neither shows variable absorption with confident levels of > 4σ for λ2796 lines and > 3σ for λ2803 lines.

Multi-Sightline Observation of Narrow Absorption Lines in Lensed Quasar SDSS J1029+2623* †

“…As an example, we compare spectra obtained at three epochs around the strong C IV NALs at z abs = 1.8909-1.9138 (ID = 35-44) in image A and C IV NALs at z abs = 1.8909-1.9119 (ID = 41-48) in image B as shown in Figure 9. These NALs are obviously not variable, which is consistent with the past result that NALs with large ejection velocities are rarely variable (Chen et al 2015).…”

“…Among several criteria, i) time variability, ii) partial coverage, and iii) line locking are the most reliable properties to distinguish intrinsic NALs from intervening NALs (Barlow & Sargent 1997;Hamann et al 1997a, and references therein). When compared with broad intrinsic absorption lines, intrinsic NALs are less likely to vary (Misawa et al 2014a;Chen et al 2015) and when they do vary, their variation amplitude is small (Wise et al 2004;Misawa et al 2014a). Therefore, the variability criterion does not offer an efficient way of identifying intrinsic NALs.…”

A Catalog of High-Velocity CIV Mini-BALs in the VLT-UVES and Keck-HIRES Archives

“…The variability in J160455+381214 was studied previously by Misawa et al (2005); Bachev et al (2005); Misawa et al (2007b); Carini et al (2007); Misawa et al (2014); Horiuchi et al (2016) using data from other telescopes, mainly Subaru. The variability in J160843+071508 was studied by MacLeod et al (2012); Chen et al (2015) using spectra from the SDSS, and the variability in J212329-005052 was studied in detail by Hamann et al (2011) using the same data as our current study. There is no previous study to our knowledge of the line variability in J175603+574848.…”

Light Variation Analysis of Mini-BAL in the SDSS J024304.68+000005.4 Spectrum

“…引言 在当今的大数据时代，斯隆数字化巡天(Sloan Digital Sky Survey, SDSS)为我们带来了极为庞大的光 谱数据，其中类星体光谱就达到几十万个[1]。类星体(QSO, Quasar)是活动星系核(AGN)的一种，它距离 我们极为遥远并且光度异常大。AGN 按其不同的观测特征可分为不同的类型，根据目前大家普遍接受的 AGN 统一模型[2] [3]， 不同的观测特征是由于星系核心与观测者之间有不同的朝向， ANG 的主要结构为： 1) 超大质量黑洞(SMBH)，类星体的中心就是超大质量的黑洞，质量约为 10 16~1 0 10 个太阳的质量；2) 吸 积盘(AD)，围绕着超大质量黑洞旋转的最内层物质为吸积盘；3) 宽线区(BLR)：吸积盘往外就是宽线区， 由许多高温云团所组成；4) 尘埃环(TOUR)，宽线区往外则为尘埃环，由尘埃和气体组成的环状物质； 5) 窄线区(NLR)，位于尘埃环以外，由密度较小的气体云团组成；6) 喷流(jet)，并不是所有的 AGN 都可 以观测到喷流，尺度较大，约为 10 kpc，甚至可达到 1 Mpc。目前，多数研究集中在 mini-BAL 如何变成更强的 BAL，而较少研究 mini-BAL 与窄吸收线的变化。 基于这点，本文重点研究不同观测间下 mini-BAL 与 NAL 的变化关系。在文献[12]证认的 52 个具有 The parameters of mini-BAL for SDSS J024304.68+000005.4 表 1. SDSS J024304.68+000005.4 的 mini-BAL 吸收线参数 The variation of the CIVλλ1548,1551 absorption doubles.…”

“…SDSS J024304.68+000005.4 的 mini-BAL 吸收线参数 The variation of the CIVλλ1548,1551 absorption doubles. The black diamond indicates the sum of the equivalent width of CIVλ1548 and CIVλ1551, the blue square indicates the sum of the equivalent width of line3, line4 and line5, and 可以看出， 在误差范围内， CIVλλ1548,1551 的等值宽度在第 1 次至第 4 次的观测时间内(∆MJD = 378)基本保持不变。但从第 4 次到第 6 次的观测时间内(∆MJD = 3251)，等值宽度有明显的变化。在第 4 次到第五次的观测时间内(∆MJD = 3048)， CIVλ1548+CIVλ1551 的等值宽度之和由大变小， 这与文献[12] 中 CIVλλ1548,1551 变弱的结论是一致的。但在第 5 次到第 6 次的观测时间内(∆MJD = 203) ，…”