Luminous Compact Blue Galaxies in the Local Universe

Abstract

We use the KPNO International Spectroscopic Survey (KISS) for emission-line galaxies to identify and describe a sample of local analogs to the luminous compact blue galaxies (LCBGs) that are observed to be abundant at intermediate and high redshift. The sample is selected using criteria believed effective at isolating true examples of LCBGs: SBe(B band) < 21.0 mag arcsec-2, MB < -18.5 (for H0 = 75 km s-1 Mpc-1), and B - V < 0.6. In addition, all LCBG candidates presented are selected to have star formation as their dominant form of activity. We examine the properties of our LCBGs and compare them with those of other KISS star-forming galaxies of the same absolute magnitude range. We find that the KISS LCBGs lie on the extreme end of a fairly continuous distribution of normal star-forming galaxies in the plane of surface brightness versus color. This result differs from the results of previous studies that show LCBGs at higher z to be more separate from the normal (usually nonactive) galaxies with which they are compared. On average, LCBGs have a higher tendency to emit detectable flux in the radio continuum; have higher Hα luminosities by a factor of 1.6, indicating strong star formation activity; and have slightly lower than expected metal abundances based on the luminosity-metallicity relation for KISS galaxies. We calculate the volume density of our low-z (z < 0.045) sample to be 5.4 × 10-4 h Mpc-3, approximately 4 times lower than the volume density of the LCBGs at 0.4 < z < 0.7 and ~10 times lower than the volume density of the population at 0.7 < z < 1.0.