Bright Lyman break galaxy candidates in the Sloan Digital Sky Survey First Data Release

摘要

We report the discovery of six compact starburst galaxy candidates with redshifts 2.3 < z < 2.8 and r-band magnitudes 19.8 - 20.5 in the Quasar Catalog of the Sloan Digital Sky Survey (SDSS) First Data Release. The SDSS spectra resemble the composite spectrum of Lyman break galaxies (LBGs) at z approximate to 3 (albeit with some differences and broader spectral lines), but the objects are 4 - 5 mag brighter than an "L-*" LBG. These objects could be extremely luminous LBGs, normal LBGs amplified by gravitational lensing, or a rare class of broad absorption line (BAL) quasars. In the first case, star formation rates inferred from the UV continuum luminosities, with no correction for dust extinction, are similar to 300 - 1000 M-., yr(-1), similar to those of ultraluminous infrared galaxies, but in these UV-bright objects the star formation is evidently not obscured by high dust column densities. The SDSS images show no evidence of multiple imaging or foreground lensing structures. The spectra have fairly broad absorption features and prominent high-ionization absorption but do not show high-ionization emission lines and do not resemble known BAL quasars. A rough estimate of the luminosity function of the objects is above a Schechter function extrapolation from LBGs at fainter magnitudes. Improved optical spectra and observations at X-ray, IR, and submillimeter wavelengths could help determine the nature of these remarkable objects. [References: 24]