Annu. Rev. Astron. Astrophys. 1991. 29: 499-541
Copyright © 1991 by Annual Reviews Inc. All rights reserved

Next Contents Previous

3.2 2-D Surveys

As a compromise between the depth of pencil-beam surveys and the relative shallowness of filled, three-dimensional ones, two-dimensional ``slice'' surveys offer an efficient means of testing the geometry of the galaxian distribution. Once one chooses the depth of the survey by adopting some sort of flux or angular diameter limit (generally imposed by the available catalogs), the angular thickness of the slice can be chosen to match the correlation scale-length at the median distance of the sample. For example, a sample drawn from the CGCG at a magnitude limit of 15.5, the 6° width of a CGCG strip is a convenient approximation of such optimal thickness. At the Harvard-Smithsonian Center for Astrophysics, the most ambitious effort of this nature is underway by Huchra, Geller, and collaborators. While their ultimate goal is the availability of redshifts for all CGCG galaxies with m leq 15.5 and |b| geq 40° (a sample of about 15,000 galaxies), the completion by slices maximizes scientific returns in terms of the statistical properties of the galaxian distribution. The first of the CfA slices is the 6° by 117° one presented by Huchra et al (1990) and de Lapparent et al (1986) as an extension. of the original CfA survey. It covers 8h leq R.A. leq 17h and 26.5° leq Dec. < 32.5°. This slice is a magnitude-limited survey of 1100 galaxies, complete to mcgcg = 15.5, which crosses some well studied features such as the Coma cluster. Two other slices are also complete, those between 32.5° leq Dec. < 38.5° and 38.5° leq Dec. < 44.5° (see also de Lapparent et al 1988), and several others are nearing completion (Huchra 1990, personal communication). Similar inroads are being made in the completion of their goal in the 20h to 04h region. De Lapparent et al (1988) have used complete data on two slices to estimate mean properties of the galaxian distribution.

Continuing work at Dartmouth College in collaboration with the CfA group aims at a deeper view within the region of the first CfA slice, a 1° x 100° strip to mB = 17.5 between 29° leq Dec. leq 30°. The first two reports on this effort, which will eventually include 2500 galaxies, have been given by Thorstensen et al (1989) and Wegner et al (1990a). The deepest completed effort of this type consists of an even narrower (10') strip across the Coma cluster, extending between 10h42m and 15h28m and to a magnitude of 18, which has been surveyed by Karachentev & Kopylov (1990) at the 6-m telescope of the Special Astrophysical Observatory of the USSR.