Abstract:
We present the first attempt to select AGN using long-term NIR variability. By
analysing the K-band light curves of all the galaxies in the UKIDSS Ultra Deep
Survey, the deepest NIR survey over ∼ 1 sq degree, we have isolated 393 variable
AGN candidates. A comparison to other selection techniques shows that only half
of the variable sources are also selected using either deep Chandra X-ray imaging or
IRAC colour selection, suggesting that using NIR variability can locate AGN that are
missed by more standard selection techniques. In particular, we find that long-term
NIR variability identifies AGN at low luminosities and in host galaxies with low stellar
masses, many of which appear relatively X-ray quiet.
