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Quasar Diversity from the Optical, UV, X-Ray, and Time Domain

Presentation #238.03D in the session “Quasars”.

Published onJan 11, 2021
Quasar Diversity from the Optical, UV, X-Ray, and Time Domain

A quasar population that spans the extrema from a broad-line region that is completely disk-dominated to largely wind-dominated can explain the observed diversity of optical-UV quasar spectra. It is thought that the dominant component (disk or wind) is dependent on L/LEdd. The relationship between the CIV equivalent width and blueshift reflect this model. These parameters are therefore able to encapsulate the majority of quasar diversity in broad emission-line properties at high redshift. However, the differences between intermediate and extreme regions in this parameter space are not well known. We apply novel methodologies to explore these differences in complementary domains. In each of our investigations we use Independent Component Analysis (ICA), a computational technique capable of reconstructing spectra in a similar manner to PCA (Principal Component Analysis) with fewer restrictions. The ICA weights encode the correlations between spectral features. We must first understand the accuracy with which single-epoch spectroscopy is able to place quasars in emission-line parameter space when multi-epoch spectroscopy does not exist. We study the variability of the CIV parameters over time in a subset of quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSSRM) sample. We investigate the onset luminosity of quasar accretion disk winds using UV-optical spectra from HST and SDSS. We analyze the differences in optical and X-ray properties among X-ray weak quasars as a function of a radiation line-driven wind, using SDSS and Chandra. Finally, we perform the same analysis on quasars which possess similar BELR properties but varying X-ray properties.

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