Charles L. Steinhardt, John D. Silverman
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.
View original:
http://arxiv.org/abs/1109.0537
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