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Published January 1, 2009 | Published
Journal Article Open

Extended emission-line regions : remnants of quasar superwinds

Abstract

We give an overview of our recent integral-field-unit spectroscopy of luminous extended emission-line regions (EELRs) around low-redshift quasars, including new observations of five fields. Previous work has shown that the most luminous EELRs are found almost exclusively around steep-spectrum radio-loud quasars, with apparently disordered global velocity fields, and little, if any, morphological correlation with either the host galaxy or the radio structure. Our new observations confirm and expand these results. The EELRs often show some clouds with velocities exceeding 500 km s^(–1), ranging up to 1100 km s^(–1), but the velocity dispersions, with few exceptions, are in the 30-100 km s^(–1) range. Emission-line ratios show that the EELRs are clearly photoionized by the quasars. Masses of the EELRs range up to 10^(10) M☉. Essentially all of the EELRs show relatively low metallicities, and they are associated with quasars that, in contrast to most, show similarly low metallicities in their broad-line regions. The two objects in our sample that do not have classical double-lobed radio morphologies (3C 48, with a compact-steep-spectrum source; Mrk 1014, radio quiet, but with a weak compact-steep-spectrum source) are the only ones that appear to have recent star formation. While some of the less luminous EELRs may have other origins, the most likely explanation for those in our sample is that they are examples of gas swept out of the host galaxy by a large-solid-angle blast wave accompanying the production of the radio jets. The triggering of the quasar activity is almost certainly the result of the merger of a gas-rich galaxy with a massive, gas-poor galaxy hosting the supermassive black hole.

Additional Information

© 2009 The American Astronomical Society. Received 2008 June 10, accepted for publication 2008 September 5. Published 2008 December 1. Print publication: Issue 1 (2009 January 1). Based in part on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina). Gemini Program ID: GN-2007A-Q-43 and GN-2007B-Q-12. We thank the Gemini North staff for carrying out the GMOS IFU observations. We also thank the anonymous referee for a careful reading of the manuscript and for useful comments that helped improve the presentation. This research has been partially supported by NSF grants AST 03-07335 and AST 08-07900. The authors recognize the very significant cultural role that the summit of Mauna Kea has within the indigenous Hawaiian community, and we are grateful to have had the opportunity to conduct observations from it. Online-only material: color figures.

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August 22, 2023
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