Characterization of AGN Variability in the Optical and Near
Infrared Regimes

Paula Sanchez, Universidad de Chile

In preparation for the Large Synoptic Survey Telescope (LSST), which will
revolutionize time-domain astronomy, it is critical that we understand
variable phenomena as deeply as possible. Variability is arguably the defining
feature of Active Galactic Nuclei (AGN), and is observed in every
waveband, so variability studies are fundamental to understanding the
extreme physical conditions of accretion disks near supermassive black
holes. Several efforts have analyzed variability in the optical. However,
to relate the variability and physical properties of AGN, we need well
sampled light curves, which are still rare. At the same time very little
is known about variability in the near infrared (NIR). At low redshift
this waveband gives us information about the dust surrounding the
accretion disk; at high redshift it tells us about the accretion disk
itself. In this talk I will present the current status of our QUEST-La
Silla AGN variability survey. We are using the QUEST camera on the
ESO-Schmidt telescope to obtain well sampled optical light curves of AGN
in well-studied extragalactic fields that already have multiwavelength
observations. The survey uses a broadband filter, the Q-band, similar to
the union of the g and the r filters. I will present our results on
variability-based AGN selection and AGN variability characterization in
the optical regime, using single and stacked images. In addition, I will
present our statistical study of the NIR variability of AGN in the COSMOS
fields, using UltraVISTA data. This dataset gives us a huge sample of light
curves, allowing us to construct a global description of the nature of
AGNs for different ranges of redshift, and for different levels of
obscuration. By combining both surveys we expect to have a better
understanding of the differences between the various classes of AGN.