The rest-frame ultraviolet spectra of UV-selected active galactic nuclei at z ∼ 2-3

Kevin N. Hainline, Alice E. Shapley, Jenny E. Greene, Charles C. Steidel

Research output: Contribution to journalArticle

54 Scopus citations

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 ∼103kms-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.

Original languageEnglish (US)
Article number31
JournalAstrophysical Journal
Volume733
Issue number1
DOIs
StatePublished - May 20 2011
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • cosmology: observations
  • galaxies: active
  • galaxies: evolution
  • galaxies: high-redshift
  • galaxies: nuclei

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