Ultradeep Ks Imaging in the GOODS-N
  We present an ultradeep Ks-band image that covers 0.5*0.5 deg^2 centered on
the Great Observatories Origins Deep Survey-North (GOODS-N). The image reaches
a 5 \sigma depth of Ks(AB) = 24.45 in the GOODS-N region, which is as deep as
the GOODS-N Spitzer Infrared Array Camera (IRAC) 3.6 \mu m image. We present a
new method of constructing IRAC catalogs that uses the higher spatial
resolution Ks image and catalog as priors and iteratively subtracts fluxes from
the IRAC images to estimate the IRAC fluxes. Our iterative method is different
from the \chi^2 approach adopted by other groups. We verified our results using
data taken in two different epochs of observations, as well as by comparing our
colors with the colors of stars and with the colors derived from model spectral
energy distributions (SEDs) of galaxies at various redshifts. We make available
to the community our WIRCam Ks-band image and catalog (94951 objects in 0.25
deg^2), the Interactive Data Language (IDL) pipeline used for reducing the
WIRCam images, and our IRAC 3.6 to 8.0 \mu m catalog (16950 objects in 0.06
deg^2 at 3.6 \mu m). With this improved Ks and IRAC catalog and a large
spectroscopic sample from our previous work, we study the color-magnitude and
color-color diagrams of galaxies. We compare the effectiveness of using Ks and
IRAC colors to select active galactic nuclei (AGNs) and galaxies at various
redshifts. We also study a color selection of z = 0.65--1.2 galaxies using the
Ks, 3.6 \mu m, and 4.5 \mu m bands.
