Galaxy number counts from the Sloan Digital Sky Survey commissioning data

We present bright galaxy number counts in five broad bands (u', g', r', i', z') from imaging data taken during the commissioning phase of the Sloan Di gital Sky Survey (SDSS). The counts are derived from two independent stripe s of imaging scans along the celestial equator, one each toward the norther n and the southern Galactic cap, covering about 230 and 210 deg(2), respect ively. A careful study is made to verify the reliability of the photometric catalog. For galaxies brighter than r* = 16, the catalog produced by autom ated software is examined against eye inspection of all objects. Statistica lly meaningful results on the galaxy counts are obtained in the magnitude r ange 12 less than or equal to r* less than or equal to 21, using a sample o f 900,000 galaxies. The counts from the two stripes differ by about 30% at magnitudes brighter than r* = 15.5, consistent with a local 2 sigma fluctua tion due to large-scale structure in the galaxy distribution. The shape of the number counts-magnitude relation brighter than r* = 16 is well characte rized by N proportional to 10(0.6m), the relation expected for a homogeneou s galaxy distribution in a "Euclidean" universe. In the magnitude range 16 <r* <21, the galaxy counts from both stripes agree very well and follow the prediction of the no-evolution model, although the data do not exclude a s mall amount of evolution. We use empirically determined color transformatio ns to derive the galaxy number counts in the B and I-814 bands. We compute the luminosity density of the universe at zero redshift in the five SDSS ba nds and in the B band. We find L-B = 2.4 +/- 0.4 x 10(8) L-. h Mpc(-3), for a reasonably wide range of parameters of the Schechter luminosity function in the B band.