A UV to Mid-IR Study of AGN Selection
  We classify the spectral energy distributions (SEDs) of 431,038 sources in
the 9 sq. deg Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). There
are up to 17 bands of data available per source, including ultraviolet (GALEX),
optical (NDWFS), near-IR (NEWFIRM), and mid-infrared (IRAC/MIPS) data, as well
as spectroscopic redshifts for ~20,000 objects, primarily from the AGN and
Galaxy Evolution Survey (AGES). We fit galaxy, AGN, stellar, and brown dwarf
templates to the observed SEDs, which yield spectral classes for the Galactic
sources and photometric redshifts and galaxy/AGN luminosities for the
extragalactic sources. The photometric redshift precision of the galaxy and AGN
samples are sigma/(1+z)=0.040 and sigma/(1+z)=0.169, respectively, with the
worst 5% outliers excluded. Based on the reduced chi-squared of the SED fit for
each SED model, we are able to distinguish between Galactic and extragalactic
sources for sources brighter than I=23.5. We compare the SED fits for a
galaxy-only model and a galaxy+AGN model. Using known X-ray and spectroscopic
AGN samples, we confirm that SED fitting can be successfully used as a method
to identify large populations of AGN, including spatially resolved AGN with
significant contributions from the host galaxy and objects with the emission
line ratios of "composite" spectra. We also use our results to compare to the
X-ray, mid-IR, optical color and emission line ratio selection techniques. For
an F-ratio threshold of F>10 we find 16,266 AGN candidates brighter than I=23.5
and a surface density of ~1900 AGN per deg^2.
