****************************************** * * * UDS K-selected catalog * * described in Williams et al. 2008 * * Current version 1.0, 4 June 2008 * * * ****************************************** Overview -------- We present a catalog of objects selected from the UKIRT Infrared Deep Sky Survey -- Ultra Deep Survey (UKIDSS-UDS) Data Release 1 K-band image. Fully matched fixed aperture photometry is available for eight bands of overlapping data: K and J from UDS, BRi'z' from the Subaru-XMM Deep Survey (SXDS) Early Data Release, and IRAC 3.6 and 4.5 micron from SWIRE. Full details of the image processing, matching, and photometry can be found in the catalog release paper by Williams et al. (2008), at arXiv:0806.0625. Photometric redshifts, calculated with the EAZY code (Brammer, van Dokkum, & Coppi 2008; www.astro.yale.edu/eazy/) are also provided. The Photometric Catalog ----------------------- Objects were detected in the UDS DR1 K-band image using SExtractor; all objects falling on bad pixels in the K band are excluded. Fluxes in the optical and near-IR bands are measured in fixed 1.75-arcsecond diameter apertures from the PSF- and astrometrically-matched images, while SWIRE IRAC fluxes were originally measured in 3-arcsecond apertures; the values given in the catalog have been corrected to account for the differences between the IRAC and optical/NIR PSFs and aperture sizes. "Total" fluxes for each object, computed using SExtractor's elliptical aperture, are also given. All fluxes are normalized to an AB zeropoint of 25, such that: magAB = 25.0-2.5*log10(flux) Flags are included in the last four columns of the catalog to indicate possible or known bad data (e.g., K-detected objects that fall on readout streaks or other artifacts in the optical images, regions not covered by SXDS or SWIRE, etc). Generally values of 0 indicate no known problems; if you're being particularly careful/conservative, it might be wise to exclude anything with nonzero flag values. The structural parameters Kr50, Keps and Kang are those automatically generated by SExtractor and should be taken as rough estimates at best. The data columns are as follows: id: running ID ra, dec: J2000 right ascension and declination Xf, Xe: 1.75" aperture flux and 1-sigma error in band X (X=BRizJK) Ktot, Ktote: K-band flux and error in the "total" aperture f36, e36, f45, e45: IRAC 3.6/4.5 micron fluxes and errors Kr50, Keps, Kang: K-band half-light radius, ellipticity, position angle Opt_badpix: Optical bad pixel flag (0=good data, 1=bad pixel in one or more of the BRi'z' images) IRAC_badpix: Mid-IR bad pixel flag (0=good, 1=bad) no_opt: flag, 1=object was not detected in a summed B+R+i+z image (and is thus highly likely to be spurious or an artifact) sex_flag: Internal flag generated by SExtractor Photometric Redshift catalog ---------------------------- We calculated photometric redshifts using the EAZY code with the default template set and template error function at an amplitude of 0.2 (which produced the best photz-specz comparison for this particular data set). Potential users of these data are strongly encouraged to read the full description of the EAZY algorithm, inputs, parameters, outputs, etc. found at http://www.astro.yale.edu/eazy/; a brief summary of the columns of the phot-z catalog follows: id: running ID (matched to photometric catalog) z_spec: unused z_a: photometric redshift derived without the K luminosity prior z_m1: P(z) weighted redshift without the K luminosity prior chi_a: minimum chi^2 value without the prior z_p, chi_p, z_m2: best-fit redshift, chi^2, and P(z)-weighted redshift WITH the K luminosity prior odds: parameter indicating the presence of a second chi^2 minimum (1=no second minimum); see EAZY paper! l/u 68/95/99: lower and upper 68%/95%/99% confidence intervals nfilt: number of filters used to derive the photz solution For the catalog paper, we used the best-fit redshift with the luminosity prior, "z_p"