Bibcode
Krogager, J.-K.; Fynbo, J. P. U.; Heintz, K. E.; Geier, S.; Ledoux, C.; Møller, P.; Noterdaeme, P.; Venemans, B. P.; Vestergaard, M.
Bibliographical reference
The Astrophysical Journal, Volume 832, Issue 1, article id. 49, 21 pp. (2016).
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11
2016
Journal
Citations
24
Refereed citations
23
Description
We present the results of a new spectroscopic survey for dusty
intervening absorption systems, particularly damped Lyα absorbers
(DLAs), toward reddened quasars. The candidate quasars are selected from
mid-infrared photometry from the Wide-field Infrared Survey Explorer
combined with optical and near-infrared photometry. Out of 1073
candidates, we secure low-resolution spectra for 108 using the Nordic
Optical Telescope on La Palma, Spain. Based on the spectra, we are able
to classify 100 of the 108 targets as quasars. A large fraction (50%) is
observed to have broad absorption lines (BALs). Moreover, we find six
quasars with strange breaks in their spectra, which are not consistent
with regular dust reddening. Using template fitting, we infer the amount
of reddening along each line of sight ranging from A(V) ≈ 0.1 to 1.2
mag (assuming a Small Magellanic Cloud extinction curve). In four cases,
the reddening is consistent with dust exhibiting the 2175 Å
feature caused by an intervening absorber, and for two of these, an Mg
ii absorption system is observed at the best-fit absorption redshift. In
the rest of the cases, the reddening is most likely intrinsic to the
quasar. We observe no evidence for dusty DLAs in this survey. However,
the large fraction of BAL quasars hampers the detection of absorption
systems. Out of the 50 non-BAL quasars, only 28 have sufficiently high
redshift to detect Lyα in absorption.