CLASH: Accurate Photometric Redshifts with 14 HST bands in Massive
  Galaxy Cluster Cores
  We present accurate photometric redshifts for galaxies observed by the
Cluster Lensing and Supernova survey with Hubble (CLASH). CLASH observed 25
massive galaxy cluster cores with the Hubble Space Telescope in 16 filters
spanning 0.2 - 1.7 $\mu$m. Photometry in such crowded fields is challenging.
Compared to our previously released catalogs, we make several improvements to
the photometry, including smaller apertures, ICL subtraction, PSF matching, and
empirically measured uncertainties. We further improve the Bayesian Photometric
Redshift (BPZ) estimates by adding a redder elliptical template and by
inflating the photometric uncertainties of the brightest galaxies. The
resulting photometric redshift accuracies are dz/(1+z) $\sim$ 0.8\%, 1.0\%, and
2.0\% for galaxies with I-band F814W AB magnitudes $<$ 18, 20, and 23,
respectively. These results are consistent with our expectations. They improve
on our previously reported accuracies by a factor of 4 at the bright end and a
factor of 2 at the faint end. Our new catalog includes 1257 spectroscopic
redshifts, including 382 confirmed cluster members. We also provide stellar
mass estimates. Finally, we include lensing magnification estimates of
background galaxies based on our public lens models. Our new catalog of all 25
CLASH clusters is available via MAST. The analysis techniques developed here
will be useful in other surveys of crowded fields, including the Frontier
Fields and surveys carried out with J-PAS and JWST.
