A search for lyman break galaxies in the Chandra Deep Field South using swift ultraviolet/optical telescope

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 on board Swift to discover 0.5 < z < 2 Lyman break galaxies (LBGs). UVOT has covered 266 arcmin² 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 Great Observatories Origins Deep Survey (GOODS) South, Multiwavelength Survey by Yale-Chile, 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 stellar masses of 〈logM _*/M_⊙〉 = 9.4 0.6, which is slightly lower than z 3 LBGs (〈logM _*/M_⊙〉 = 10.2 0.4) and slightly higher compared with the z 1 CDF-S galaxies (〈logM _*/M_⊙〉 = 8.7 0.7). Similarly, our sample of z 1 LBGs has SFRs (derived using both ultraviolet and infrared data, where available) of 〈logSFR/(M_⊙ yr^-1)〉 = 0.7 0.6, nearly an order of magnitude lower than z 3 LBGs (〈logSFR/M _⊙ yr^-1〉 = 1.5 0.4), but slightly higher than the comparison z 1 sample of CDF-S galaxies (〈logSFR/M_⊙ yr^-1〉 = 0.2 0.7). We find that our z 1 UV-dropouts have 〈A _FUV〉 = 2.0 1.0, which is higher than z 3 LBGs (〈A _FUV〉 = 1.0 0.5), but similar to the distribution of dust attenuations in the other CDF-S galaxies (〈A _FUV〉 2.8 1.5). 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.