On the CCD calibration of Zwicky galaxy magnitudes and the properties of nearby field galaxies

We present CCD (charge-coupled device) photometry for galaxies around 204 b right (m(Z) < 15.5) Zwicky galaxies in the equatorial extension of the APM Galaxy Survey, sampling an area over 400 deg(2), which extends 6 h in right ascension. We fit a best linear relation between the Zwicky magnitude syst em, m(Z), and the CCD photometry, B-CCD, by doing a likelihood analysis tha t corrects for Malmquist bias. This fit yields a mean scale error in Zwicky of 0.38 mag mag(-1): i.e. Delta m(Z) similar or equal to (0.62 +/- 0.05)De lta B-CCD and a mean zero-point of [B-CCD - m(Z)] = -0.35 +/- 0.15 mag. The scatter around this fit is about 0.4 mag, Correcting the Zwicky magnitude system with the best-fitting model results in a 60 per cent lower normaliza tion and 0.35-mag brighter M-* in the luminosity function. This brings the CfA2 luminosity function closer to the other low-redshift estimations (e.g. Stromlo-APM or LCRS). We find a significant positive angular correlation o f magnitudes and position in the sky at scales smaller than about 5 arcmin, which corresponds to a mean separation of 120 h(-1) kpc. We also present c olours, sizes and ellipticities for galaxies in our fields, which provides a good local reference for the studies of galaxy evolution.