Photometry of a complete sample of faint galaxies

Abstract

Techniques are developed for the automatic measurement of the colors and magnitudes of a complete sample of very faint galaxies. The observations consist of photographic surface photometry in two wavebands for approximately 20,000 galaxies in two widely separated, high-latitude fields, each having an area of approximately 1080 sq arcmin. The photometric zero points are derived directly from faint stars in the same fields measured photoelectrically by other observers. The photometry of the galaxy sample is complete to a limit about 10 times fainter than has been systematically investigated before. The sample is characterized by a population of galaxies which becomes bluer with increasing faintness and which increases steeply in number with increasing faintness in the blue waveband.