M. U. SubbaRao | Searcharxiv

arXiv1997

The Evolution of the Global Star Formation History as Measured from the Hubble Deep Field

The Hubble Deep Field (HDF) is the deepest set of multicolor optical photometric observations ever undertaken, and offers a valuable data set with which to study galaxy evolution. Combining the optical WFPC2 data with ground-based near-infrared photometry, we derive photometrically estimated redshifts for HDF galaxies with J<23.5. We demonstrate that incorporating the near-infrared data reduces the uncertainty in the estimated redshifts by approximately 40% and is required to remove systematic uncertainties within the redshift range 1 2, and bridge the redshift gap between those two samples. The overall star formation or metal enrichment rate history is consistent with the predictions of Pei and Fall (1995) based on the evolving HI content of Lyman-alpha QSO absorption line systems.

astro-ph↗

arXiv1996

Luminosity Functions from Photometric Redshifts I: Techniques

The determination of the galaxy luminosity function is an active and fundamental field in observational cosmology. In this paper we propose a cost effective way of measuring galaxy luminosity functions at faint magnitudes. Our technique employs the use of galaxy redshifts estimated from their multicolor photometry (Connolly et al. 1995). Associated with the redshift estimate is a well defined error distribution. We have derived a variant of Lynden-Bell's (1971) C--method that considers, for each galaxy, the probability distribution in absolute magnitude resultant from the redshift error. This technique is tested through simulations and potential biases are quantified. We then apply the technique to a sample of galaxies with multicolor photometric data at moderately faint (B=23) limits, and compare the results to a subset of these data with spectroscopic redshifts. We find that the luminosity function derived from the photometric redshifts is consistent with that determined from spectroscopic redshifts.

astro-ph↗