Detection of rest-frame optical lines from x-shooter spectroscopy of weak emission-line quasars
Author
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Plotkin, Richard
Author
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Shemmer, Ohad
Author
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Trakhtenbrot, Benny
Author
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Anderson, Scott
Author
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Brandt, W.
Author
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Fan, Xiaohui
Author
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Gallo, Elena
Author
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Lira Teillery, Paulina
Author
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Luo, Bin
Author
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Richards, Gordon
Author
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Schneider, Donald
Author
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Strauss, Michael
Author
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Wu, Jianfeng
Admission date
dc.date.accessioned
2015-06-16T19:31:11Z
Available date
dc.date.available
2015-06-16T19:31:11Z
Publication date
dc.date.issued
2015-06-01
Cita de ítem
dc.identifier.citation
The Astrophysical Journal, 805:123 (18pp), 2015 June 1
en_US
Identifier
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doi:10.1088/0004-637X/805/2/123
Identifier
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https://repositorio.uchile.cl/handle/2250/131133
General note
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Artículo de publicación ISI
en_US
Abstract
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Over the past 15 yr, examples of exotic radio-quiet quasars with intrinsically weak or absent broad emission line
regions (BELRs) have emerged from large-scale spectroscopic sky surveys. Here, we present spectroscopy of
seven such weak emission line quasars (WLQs) at moderate redshifts (z = 1.4–1.7) using the X-shooter
spectrograph, which provides simultaneous optical and near-infrared spectroscopy covering the rest-frame
ultraviolet (UV) through optical. These new observations effectively double the number of WLQs with
spectroscopy in the optical rest-frame, and they allow us to compare the strengths of (weak) high-ionization
emission lines (e.g., C IV) to low-ionization lines (e.g., Mg II, Hβ, Hα) in individual objects. We detect broad
Hβ and Hα emission in all objects, and these lines are generally toward the weaker end of the distribution expected
for typical quasars (e.g., Hβ has rest-frame equivalent widths ranging from 15–40 Å). However, these lowionization
lines are not exceptionally weak, as is the case for high-ionization lines in WLQs. The X-shooter spectra
also display relatively strong optical Fe II emission, Hβ FWHM 4000 km s−1
, and significant C IV blueshifts
(≈1000–5500 km s−1
) relative to the systemic redshift; two spectra also show elevated UV Fe II emission, and an
outflowing component to their (weak) Mg II emission lines. These properties suggest that WLQs are exotic
versions of “wind-dominated” quasars. Their BELRs either have unusual high-ionization components, or their
BELRs are in an atypical photoionization state because of an unusually soft continuum.