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Session 52 - Source Surveys and CMB Radiation.
Display session, Wednesday, June 10
Redshifts have been obtained for the sample of 189 objects with K < 20 mag in a field 2 x 7.3 arc-min^2 at J005323+1234. with 84% completeness, as well as for 15 additional nearby objects. We find that the extremely red objects in the sample with redshifts are absorption line dominated systems with z \approx 1.
As shown in our earlier work, more than half of the galaxies lie in five peaks in the redshift histogram. We find that the strong redshift peaks are populated largely by galaxies with spectra dominated by absorption lines. Emission line dominated galaxies avoid these structures, which have velocity dispersions that are too small for clusters of galaxies. These structures appear to be bound groups of galaxies similar to groups observed locally with masses larger than that of the Local Group but smaller than that of a typical cluster of galaxies. Groups of galaxies, like clusters of galaxies, must therefore be stable structures that have been in existence for a long time; they have not collapsed and formed recently.
The most luminous galaxies appear to reside almost exclusively in these redshift peaks. Their clustering properties must be quite different from those of the emission-line dominated galaxies. Furthermore the spectral type assigned to the brightest galaxies in strong peaks shifts progressively away from absorption dominated quiescent systems at low z to systems with significant signs of recent star formation at higher z.
Even those galaxies not in the strongest redshift peaks often are found in small groups. Only 9% of the sample may be truly isolated. Most of these apparently isolated galaxies may well have companions fainter than the survey limit or just outside the spatial boundary of the survey.
Program listing for Wednesday