The Rest-frame Ultraviolet Spectra of UV-selected Active Galactic Nuclei at z ~ 2-3
Abstract
We present new results for a sample of 33 narrow-lined UV-selected active galactic nuclei (AGNs), identified in the course of a spectroscopic survey for star-forming galaxies at z ~ 2-3. The rest-frame UV composite spectrum for our AGN sample shows several emission lines characteristic of AGNs, as well as interstellar absorption features detected in star-forming Lyman break galaxies (LBGs). We report a detection of N iv] λ1486, which has been observed in high-redshift radio galaxies, as well as in rare optically selected quasars. The UV continuum slope of the composite spectrum is significantly redder than that of a sample of non-AGN UV-selected star-forming galaxies. Blueshifted Si iv absorption provides evidence for outflowing highly ionized gas in these objects at speeds of ~10^3 km s^(–1), quantitatively different from what is seen in the outflows of non-AGN LBGs. Grouping the individual AGNs by parameters such as the Lyα equivalent width, redshift, and UV continuum magnitude allows for an analysis of the major spectroscopic trends within the sample. Stronger Lyα emission is coupled with weaker low-ionization absorption, which is similar to what is seen in the non-AGN LBGs, and highlights the role that cool interstellar gas plays in the escape of Lyα photons. However, the AGN composite does not show the same trends between Lyα strength and extinction seen in the non-AGN LBGs. These results represent the first such comparison at high redshift between star-forming galaxies and similar galaxies that host AGN activity.
Additional Information
© 2011 The American Astronomical Society. Received 2010 November 24; accepted 2011 March 16; published 2011 April 29. Based, in part, on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation. We thank Dawn Erb and Max Pettini for their helpful discussions. We also acknowledge the referee, David Alexander, for a thorough and constructive report, which significantly improved the paper. A.E.S. acknowledges support from the David and Lucile Packard Foundation. C.C.S. acknowledges additional support from the John D. and Catherine T. MacArthur Foundation and the Peter and Patricia Gruber Foundation. We wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, most of the observations presented herein would not have been possible.Attached Files
Published - Hainline2011p13968Astrophys_J.pdf
Accepted Version - 1012.0075.pdf
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Additional details
- Eprint ID
- 23840
- Resolver ID
- CaltechAUTHORS:20110531-114638789
- David and Lucile Packard Foundation
- John D. and Catherine T. MacArthur Foundation
- Peter and Patricia Gruber Foundation
- W. M. Keck Foundation
- Created
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2011-05-31Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field