A Catalog of Color-based Redshift Estimates for z <~ 4 Galaxies in the   Hubble Deep Field
  We derive simple empirical color-redshift relations for $z\la 4$ 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 $\sigma_z\simeq 0.03$ to 0.1 for $z\la 2$ galaxies, and from $\sigma_z\simeq 0.14$ to 0.25 for $z\ga 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 $z\la 4$ 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 $z\la 4$. 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 $z\sim 1$ and that are consistent with those identified in spectroscopic probes of the HDF. 
Yun Wang, Neta Bahcall, & Edwin L. Turner (Princeton)