Optical surface photometry of eight spiral galaxies studied in Westerbork.

Optical surface photometry from sky-limited IIIa-J plates of eight spiral galaxies observed in the HI 21-cm line in the Westerbork telescope is presented. The following points are discussed: (1) the reduction procedures were subjected to several tests, and internal and external comparisons show that the magnitude scale is reliable fainter than 22 magnitudes/sq arcsec and accurate to about 0.04 mag per magnitude interval. The zero point of the magnitude scale is derived from profiles of bright field stars and is estimated to be correct to plus or minus 0.2 mag; (2) the distributions of light in three edge-on galaxies show marginal evidence for warps in stellar disks accompanying the HI-warps, and the effects observed in the optical isophote maps can also be explained as spiral structure in imperfectly edge-on disks; (3) the radial distributions of light are determined for five galaxies which show much detail due to the disk structure, and exponential functions give only a rough representation of the radial profiles; (4) a comparison of the data with that of the IIIa-F plate of NGC 5055 shows a significant reddening beyond about 10 kpc on at least one-half of the galaxy.