Deep Keck u-band imaging of the Hubble Ultra Deep Field: A catalog of z~3 Lyman Break Galaxies

TL;DR

This paper presents a highly sensitive u-band imaging survey of the Hubble Ultra Deep Field, identifying 407 z~3 Lyman break galaxies and improving photometric redshift accuracy for studying early galaxy formation.

Contribution

It introduces a deep u-band image from Keck that enhances the selection and redshift estimation of z~3 LBGs, enabling detailed morphological and evolutionary studies.

Findings

Catalog of 407 z~3 LBGs with u-band data

Significant reduction in redshift degeneracy

Enhanced accuracy of photometric redshifts for high-z galaxies

Abstract

We present a sample of 407 z~3 Lyman break galaxies (LBGs) to a limiting isophotal u-band magnitude of 27.6 mag in the Hubble Ultra Deep Field (UDF). The LBGs are selected using a combination of photometric redshifts and the u-band drop-out technique enabled by the introduction of an extremely deep u-band image obtained with the Keck I telescope and the blue channel of the LRIS spectrometer. The Keck u-band image, totaling 9 hours of integration time, has a one sigma depth of 30.7 mag arcsec^-2, making it one of the most sensitive u-band images ever obtained. The u-band image also substantially improves the accuracy of photometric redshift measurements of ~50% of the z~3 Lyman break galaxies, significantly reducing the traditional degeneracy of colors between z~3 and z~0.2 galaxies. This sample provides the most sensitive, high-resolution multi-filter imaging of reliably identified z~3 LBGs for morphological studies of galaxy formation and evolution and the star formation efficiency of gas at high redshift.