Faint blue galaxies - High or low redshift?

Abstract

The results of two new redshift surveys carried out with the Low Dispersion Survey Spectrograph (LDSS) on the Anglo-Austrian Telescope are presented. The first is an extension of the earlier LDSS deep survey, in which two of the original survey zones were reobserved and the 19 percent incompleteness in redshift identifications was reduced to just 4.5 percent. Redshifts for 19 new galaxies were obtained increasing the total number of redshifts to 104. It is concluded that at most 4.5 percent of galaxies brighter than 22.5 can have redshifs greater than 0.7. The second redshift survey studied the population of faint blue galaxies with R between 22 and 23. The redshifts of the six bluest galaxies with B-I less than 1, indicative of a near-flat spectrum in f(nu), were identified. Apart from one QSO, all the identified objects are galaxies with redshifts in the range between 0.3 and 0.9. These results are found to be consistent with both merging-dominated models for galaxy evolution and models postulating bursts of star formation in dwarf galaxies.