Disk galaxies in the outer local supercluster: optical CCD surface photometry and distribution of galaxy disk parameters.
Abstract (from CDS):
We report new B-band CCD surface photometry on a sample of 76 disk galaxies brighter than BT = 14.5 mag in the Uppsala General Catalogue of Galaxies that are confined within a volume located in the outer part of the Local Supercluster. With our earlier published I-band CCD and high signal-to-noise ratio 21 cm H I data, this paper completes our optical surface photometry campaign on this galaxy sample. As an application of this data set, the B-band photometry is used here to illustrate two selection effects that have been somewhat overlooked in the literature but that may be important in deriving the distribution function of disk central surface brightness (CSB) of disk galaxies from a diameter- and/or flux-limited sample: a Malmquist-type bias against disk galaxies with small disk scale lengths (DSLs) at a given CSB and a disk inclination-dependent selection effect that may, for example, bias toward inclined disks near the threshold of a diameter-limited selection if disks are not completely opaque in the optical. Taking into consideration these selection effects, we present a method of constructing a volume-sampling function and a way to interpret the derived distribution function of CSB and DSL. Application of this method to our galaxy sample implies that if galaxy disks are opticallythin, CSB and DSL may well be correlated in the sense that, up to an inclination-corrected limiting CSB of about 24.5.mag arcsec–2 that is adequately probed by our galaxy sample, the DSL distribution of galaxies with a lower CSB may have a longer tail toward large values unless the distribution of disk galaxies as a function of CSB rises rapidly toward faint values.