Session 76 - Star Formation in Galaxies.
Display session, Friday, January 09
Exhibit Hall,

[76.02] Spatial Distributions, Luminosity Functions, and the Star-Formation Rate Density of the Local Universe from the KPNO International Spectroscopic Survey

C. Gronwall, J. J. Salzer (Wesleyan U.), M. R. Santos, E. J. Condy (Vassar College), L. W. Brenneman (Williams College)

The emission-line galaxies discovered in the KPNO International Spectroscopic Survey (KISS) are used to investigate several fundamental properties of the population of starbursting and active galaxies. Our large sample of line-selected galaxies is particularly well suited for carrying out statistical studies because the completeness limits and selection function of the survey can be accurately determined. Here we use several hundred newly discovered emission-line galaxies to explore the spatial distribution of galaxies in a thin slice out to z \sim 0.1, to determine the B-band and H\alpha luminosity functions of actively star-forming galaxies, and to derive the star-formation rate density of the local universe. The redshifts and emission-line fluxes necessary for this work are derived from our low-dispersion objective-prism spectra.

The galaxies trace out, in a coarse way, large-scale structure features throughout this volume, going substantially beyond the region mapped by shallower redshift surveys (e.g., The Slice of the Universe). The B-band luminosity function (LF) exhibits a fairly steep faint-end slope, similar to previous studies of line-selected surveys. Such samples detect a much higher proportion of dwarf galaxies than do traditional magnitude-limited surveys, making the determination of the faint portion of the luminosity function more secure. Using the H\alpha line strengths we also determined the H\alpha luminosity function for our sample. We see substantial differences when compared with the previous work of Gallego et al.; our LF is sensitive to substantially lower luminosities and has a much steeper faint-end slope. By integrating our LF, we determine the total H\alpha luminosity density for the local universe, which in turn leads to a derivation of the local star-formation rate density. Our value is somewhat higher than that of Gallego et al., indicating that the drop off in star-formation activity between z \sim 1 and today was not as severe as previously reported.