DEEP OPTICAL GALAXY COUNTS WITH THE KECK-TELESCOPE
1995
ASTROPHYSICAL JOURNAL
We present faint galaxy counts from deep VRI images obtained with the Keck Telescope. These images reach R similar to 27 in median seeing FWHM similar to 0 ''.5-0 ''.6, and we detect a integrated galaxy number density of 7 x 10(5) deg(-2), equivalent to 3 x 10(10) galaxies in the observable universe. In addition we present median galaxy colors as a function of magnitude; bluing trends are visible in all colors to R similar to 24.5. Fainter than R similar to 24.5, however, the typical V - R color becomes redder again, V - I remains constant, and R - I becomes yet bluer. These trends are consistent with the VRI count slopes, implying a decrease in the V slope at the faintest levels, which our data support. Taking advantage of our good seeing we also present median half-light radii for faint galaxies; these show a steady decline at fainter magnitudes, leading to an intrinsic half-light radius of similar to 0 ''.2 for a typical R similar to 26 galaxy. Irrespective of the redshift distribution, the extremely high galaxy surface densities and their small intrinsic sizes are consistent with a scenario in which the majority of the very faint field population are dwarf galaxies or subgalactic units.