Deep r-Band Photometry for Northern Spiral Galaxies

Abstract

We present r-band surface photometry for 349 northern Sb-Sc UGC galaxies, from a total of 627 CCD images. For each galaxy, we present surface brightness profiles, isophotal and total magnitudes, isophotal radii, and structural parameters from exponential fits to the disk. One hundred ninety-five galaxies have been observed more than once. All nights with a photometric transformation scatter greater than 0.022 mag were rejected. Sky errors are investigated carefully and yield profiles that are reliable down to 26 r mag arcsec^-2^, Deep isophotal magnitudes are as accurate as +/-0.019, and extrapolated magnitudes are internally consistent to within 0.020. We compare visual (UGC) and CCD isophotal diameters and show that axial ratio must be included as a third parameter. Comparison with the r-band CCD photometry of Kent and Willick, and accounting for sky errors, suggest typical errors for total magnitudes of +/-0.08. Our data are also shown to be zero-pointed on the same Gunn r system as that of Kent and Willick. Ellipticity measurements agree very well except for progressively face-on galaxies where spiral structure is more conspicuous. The ellipticity internal error is less than 0.02, or about 3^deg^ for inclinations. Our internal extinction correction implies that disks are semitransparent in their outer parts. We caution that comparison of central surface brightnesses and scale lengths is complicated by the subjective nature of their measurement; extreme care must be applied when using such quantities. We measure an apparent Freeman law of (μ_0,c_) = 20.08 +/- 0.55 r mag arcsec^-2^. This magnitude-limited sample was originally derived for studies of large-scale motions in the local universe. The deep CCD photometry is also ideally suited for matching spectroscopic studies, mass modeling, galaxy structural analysis, etc.