A synoptic survey of narrow quasar absorption lines from the Sloan Digital Sky Survey

quasars: absorption lines;quasars: general

Hacker, Troy L.

关键词: quasars: absorption lines;    quasars: general;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/29590/Hacker_Troy.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Repeat spectroscopic observations from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) provide an unprecedented opportunity to study the properties of thousands of quasar absorption lines (QALs) in the time domain.Systems of QALs have proven to be one of the most sensitive and unbiased probes of baryonic matter in the high-redshift Universe.Short timescale absorption variability is one tool that has been used to characterize the origins and environments of relativistic quasar outflows.However, these studies have been limited to tens of systems due to the time and expense required for high-resolution repeat spectroscopic observations of quasars.Recently the SDSS released over 5,000 quasar spectra that were serendipitously observed on multiple nights with time separations ranging from days to years.This data set represents the largest population of repeat quasar spectra ever produced and enables a comprehensive statistical analysis of quasar absorption systems.The primary goal of this thesis is to present the results from our systematic analysis of narrow absorption line (NAL) variability.From the sample of repeat SDSS quasar spectra, we identified 2,585 QAL systems using a proprietary line-finding algorithm to create the largest ever catalog of quasar absorption systems.We developed a detailed analysis method to fit the absorption lines in these systems and measure variability.Extensive Monte Carlo simulations were conducted to characterize the occurrence of false variability due to random noise fluctuations and to determine the minimum threshold for identifying variable absorption lines.These measurements yield a total of 42 NAL systems that display no obvious systematics with respect to line strength, redshift, quasar luminosity, or time between observations.Of these, at least 12 are likely from a class known as intervening absorption systems caused by small-scale absorbing gas clouds in foreground galaxies along the line of sight to the background quasar.As such, they represent the first known detection of variable intervening absorption lines in quasar spectra.