A Lyα-only active galactic nucleus from the Sloan Digital Sky Survey

Patrick B. Hall, Erik A. Hoversten, Christy A. Tremonti, Daniel E. Vanden Berk, Donald P. Schneider, Michael A. Strauss, Gillian R. Knapp, Donald G. York, Damien Hutemékers, P. R. Newman, J. Brinkmann, Brenda Frye, Masataka Fukugita, Karl Glazebrook, Michael Harvanek, Timothy M. Heckman, Željko Ivezić, S. Kleinman, Jurek Krzesinski, Daniel C. LongEric Neilsen, Martin Niederste-Ostholt, Atsuko Nitta, David J. Schlegel, S. Snedden

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12 Scopus citations


The Sloan Digital Sky Survey has discovered a z = 2.4917 radio-loud active galactic nucleus (AGN) with a luminous, variable, low-polarization UV continuum, H I two-photon emission, and a moderately broad Lyα line (FWHM ≃ 1430 km s-1) but without obvious metal-line emission. SDSS J113658.36+024220.1 does have associated metal-line absorption in three distinct, narrow systems spanning a velocity range of 2710 km s-1. Despite certain spectral similarities, SDSS J1136+0242 is not a Lyman break galaxy. Instead, the Lyα and two-photon emission can be attributed to an extended, low-metallicity narrow-line region. The unpolarized continuum argues that we see SDSS 11136+0242 very close to the axis of any ionization cone present. We can conceive of two plausible explanations for why we see a strong UV continuum but no broad-line emission in this "face-on radio galaxy" model for SDSS J1136+0242: the continuum could be relativistically beamed synchrotron emission that swamps the broad-line emission, or more likely, SDSS J1136+0242 could be similar to PG1407+265, a quasar in which for some unknown reason the high-ionization emission lines are very broad, very weak, and highly blueshifted.

Original languageEnglish (US)
Pages (from-to)3146-3154
Number of pages9
JournalAstronomical Journal
Issue number6 1782
StatePublished - Jun 2004

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Quasars: emission lines
  • Quasars: general
  • Quasars: individual (PG 1407+265, SDSS J113658.36+024220.1)


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