Astronomy and Astrophysics – Astrophysics – High Energy Astrophysical Phenomena
Scientific paper
2011-09-02
Astronomy and Astrophysics
Astrophysics
High Energy Astrophysical Phenomena
21 pages, submitted
Scientific paper
We describe a new class of Type I quasars with narrow H\beta\ broader than 1200 km/s, above the velocity believed possible for gas in the quasar narrow-line region. We identify this group of quasars as a distinct population because of a variety of spectral and photometric signatures common to these "anomalous narrow-line quasars" (ANLs) but atypical of other quasars. One prominent signature is suppression of the [OIII]\lambda ?4959, 5007 emission-line, in many cases accompanied by broadening similar to the H\beta\ line. We demonstrate that ANLs comprise at least 11% and most likely approximately one quarter of the SDSS Type I quasar population at 0.2 < z < 0.8. The most striking feature of ANLs is a strong correlation between narrow H\beta\ width and the width of the broad component of the H\beta\ emission line. Another feature of ANLs is a diminished [OII] line, which might indicate a connection between ANLs and the interstellar mediums of their host galaxies, through reduced photoionization or star formation. We find that it is difficult to produce ANLs using the current quasar standard model.
Silverman John D.
Steinhardt Charles L.
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