A Catalog of Color-based Redshift Estimates for [ITAL][CLC]z[/CLC][/ITAL] ≲ 4 Galaxies in the Hubble Deep Field

We derive simple empirical color-redshift relations for z 4 galaxies in the Hubble Deep Field (HDF) using a linear function of three photometric colors ($U-B$, $B-V$, $V-I$). The dispersion between the estimated redshifts and the spectroscopically observed ones is small for relations derived in several separate color regimes; the dispersions range from σz 0.03 to 0.1 for z 2 galaxies, and from σz 0.14 to 0.25 for z 2 galaxies. We apply the color-redshift relations to the HDF photometric catalog and obtain estimated redshifts that are consistent with those derived from spectral template fitting methods. The advantage of these color-redshift relations is that they are simple and easy to use and do not depend on the assumption of any particular spectral templates; they provide model independent redshift estimates for z 4 galaxies using only multi-band photometry, and they apply to about 90% of all galaxies. We provide a color-based estimated redshift catalog of HDF galaxies to z 4. We use the estimated redshifts to investigate the redshift distribution of galaxies in the HDF; we find peaks in the redshift distribution that suggest large-scale clustering of galaxies to at least z~ 1 and that are consistent with those identified in spectroscopic probes of the HDF.