Line-Driven Radiative Outflows in Luminous Quasars

Authors

Rebecca A. A. Bowler, University of Cambridge, UK
Paul C. Hewett, University of Cambridge, UK
James T. Allen, University of Cambridge, UK
Gary J. Ferland, University of KentuckyFollow

Abstract

An analysis of ≃19 500 narrow ( ≲ 200 km s⁻¹) C iv λλ1548.2,1550.8 absorbers in ≃34 000 Sloan Digital Sky Survey quasar spectra is presented. The statistics of the number of absorbers as a function of outflow velocity shows that in approximately two-thirds of outflows, with multiple C iv absorbers present, absorbers are line-locked at the 500 km s⁻¹ velocity separation of the C iv absorber doublet; appearing as ‘triplets’ in the quasar spectra. Line-locking is an observational signature of radiative line-driving in outflowing material, where the successive shielding of ‘clouds’ of material in the outflow locks the clouds together in outflow velocity. Line-locked absorbers are seen in both broad absorption line (BAL) quasars and non-BAL quasars with comparable frequencies and with velocities out to at least 20 000 km s⁻¹. There are no detectable differences in the absorber properties and the dust content of single C iv doublets and line-locked C iv doublets. The gas associated with both single and line-locked C iv absorption systems includes material with a wide range of ionization potential (14–138 eV). Both single and line-locked C iv absorber systems show strong systematic trends in their ionization as a function of outflow velocity, with ionization decreasing rapidly with increasing outflow velocity. Initial simulations, employing cloudy, demonstrate that a rich spectrum of line-locked signals at various velocities may be expected due to significant opacities from resonance lines of Li-, He- and H-like ions of O, C and N, along with contributions from He ii and H i resonance lines. The simulations confirm that line-driving can be the dominant acceleration mechanism for clouds with N(H i) ≃ 10¹⁹ cm⁻².

Document Type

Article

Publication Date

11-21-2014

Notes/Citation Information

Published in Monthly Notices of the Royal Astronomical Society, v. 445, no. 1, p. 359-377.

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Digital Object Identifier (DOI)

http://dx.doi.org/10.1093/mnras/stu1730

Funding Information

PCH acknowledges support from the STFC-funded Galaxy Formation and Evolution programme at the Institute of Astronomy. JTA acknowledges the award of an STFC PhD studentship and an ARC Super Science Fellowship. GJF acknowledges support by NSF (1108928, 1109061 and 1412155), NASA (10-ATP10-0053, 10-ADAP10-0073, NNX12AH73G and ATP13-0153) and STScI (HST-AR-12125.01, HST-AR- 13245, GO-12560, HST-GO-12309 and GO-13310.002-A), and is grateful to the Leverhulme Trust for support via the award of a Visiting Professorship at Queen's University Belfast (VP1-2012-025).

Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS website is http://www.sdss.org/.

Repository Citation

Bowler, Rebecca A. A.; Hewett, Paul C.; Allen, James T.; and Ferland, Gary J., "Line-Driven Radiative Outflows in Luminous Quasars" (2014). Physics and Astronomy Faculty Publications. 282.
https://uknowledge.uky.edu/physastron_facpub/282