A Search for Lyman Break Galaxies in the CDF-S Using Swift UVOT

TL;DR

This study utilizes Swift UVOT data to identify and analyze Lyman break galaxies at redshifts 0.5<z<2 in the CDF-S, characterizing their properties and demonstrating UVOT's effectiveness in studying bright LBGs.

Contribution

First application of Swift UVOT for selecting and analyzing LBGs at intermediate redshifts, providing insights into their properties and the capabilities of UVOT for such studies.

Findings

UVOT-selected LBGs have lower stellar masses than z~3 LBGs.

Star formation rates are nearly an order of magnitude lower than at z~3.

UVOT can effectively find bright LBGs in the 0.5<z<2 range.

Abstract

(Abridged) While the Swift satellite is primarily designed to study gamma-ray bursts, its ultraviolet and optical imaging and spectroscopy capabilities are also being used for a variety of scientific programs. In this study, we use the UV/Optical Telescope (UVOT) instrument aboard Swift to discover 0.5<z<2 Lyman break galaxies (LBGs). UVOT has covered ~266 arcmin^2 at >60ks exposure time, achieving a limiting magnitude of u<24.5, in the Chandra Deep Field South (CDF-S). Applying UVOT near-ultraviolet color selection, we select 50 UV-dropouts from this UVOT CDF-S data. We match the selected sources with available multiwavelength data from GOODS-South, MUSYC, and COMBO-17 to characterize the spectral energy distributions for these galaxies and determine stellar masses, star formation rates (SFRs), and dust attenuations. We compare these properties for LBGs selected in this paper versus z~3 LBGs and other CDF-S galaxies in the same redshift range (0.5<z<2), identified using photometric redshift techniques. The z~1 LBGs have slightly lower stellar masses compared to z~3 LBGs and slightly higher stellar masses compared to the z~1 CDF-S galaxies. Similarly, our sample of z~1 LBGs has SFRs (derived using both ultraviolet and infrared data, where available) nearly an order of magnitude lower than z~3 LBGs but slightly higher than the comparison z~1 sample of CDF-S galaxies. We find that our z~1 UV-dropouts have A_FUV higher than z~3 LBGs, but is similar to the distribution of dust attenuations in the other CDF-S galaxies. Using the GOODS-South multiwavelength catalog of galaxies, we simulate a larger and fainter sample of LBGs to compare their properties with those of the UVOT-selected LBG sample. We conclude that UVOT can be useful for finding and studying the bright end of 0.5<z<2.0 LBGs.