Zusammenfassung
We quadruple the number of quasars known behind the Large Magellanic Cloud
(LMC) from 55 (42 in the OGLE-III LMC fields) to 200 by spectroscopically
confirming 169 (145 new) quasars from a sample of 845 observed candidates in
four ~3 deg^2 AAT/AAOmega fields south of the LMC center. The candidates were
selected based on their Spitzer mid-infrared colors, X-ray emission, and/or
optical variability properties in the database of the OGLE microlensing survey.
The contaminating sources can be divided into 112 young stellar objects (YSOs),
17 planetary nebulae (PNe), 39 Be and 24 blue stars, and 66 red stars. There
are also 401 targets with either featureless spectra or too low signal-to-noise
ratio for source classification. While our quasar sample is relatively complete
for I<19.2 mag, it is incomplete for fainter quasars. We would expect to find
an additional ~200 AGNs if the sample was complete to our target depth of I<21
mag. The newly discovered AGNs provide many additional reference points for
proper motion studies of the LMC, and the sample includes 10 bright AGNs (I<18
mag) potentially suitable for absorption line studies. Their primary use,
however, is for detailed studies of quasar variability, as they all have
long-term, high cadence, continuously growing light curves from the
microlensing surveys of the LMC. Completing the existing Magellanic Quasars
Survey (MQS) fields in the LMC and SMC should yield a sample of ~700
well-monitored AGNs, and expanding it to the larger regions covered by the
OGLE-IV survey should yield a sample of ~3600 AGNs.
Beschreibung
[1106.3110] The Magellanic Quasars Survey. II. Confirmation of 145 New AGN Behind the Southern Edge of the Large Magellanic Cloud
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