The properties of local poor Abell clusters and instrumentation for the study of clustered objects
Abstract
Since the identification of the Abell galaxy cluster sample in the 1950's observational cosmologists have been interested in the characteristics of these systems. However, until recently little more than their most basic properties, such as morphology and distance (from a small sample of member velocities), has been known. Some fundamental questions still remain unanswered. Do clusters form from field galaxies? Have they evolved significantly since their formation? Is their morphological type an indicator of their age? With the advent of wide-field imaging CCD's and multiplexing spectroscopic instruments, considerably more information has been accumulated for the richer clusters (those with memberships greater than 50). However, the poorer clusters, which potentially represent a transitional phase from field to the richer clusters, have received relatively little attention. This thesis represents a two element study of these objects. The first half discusses the issues involved in the construction of a multiplexing spectrographic system, specifically the Lick/LLNL Automated Multiobject Spectrograph (AMOS). Issues of systemic efficiency are examined with computer modeling and laboratory trials. The second half presents the results of a deep photometric survey of three poor clusters of galaxies out to 0.5 Abell radii. Data were taken in both V and I bands from the Johnson-Kron-Cousins system and are complete to a limiting magnitude of V = 19.5. The three clusters are located at essentially the same redshift (z = 0.07) and span the full range of Rood-Sastry morphological types. While surface distributions support the morphological typing, comparison of the three luminosity functions shows no indication of an evolutionary sequence. A composite luminosity function is presented for comparison with samples at other redshifts and richness classes.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1994
- Bibcode:
- 1994PhDT.........2D
- Keywords:
-
- Astronomical Photometry;
- Astronomical Spectroscopy;
- Galactic Clusters;
- Galactic Evolution;
- Imaging Techniques;
- Multiplexing;
- Sky Surveys (Astronomy);
- Spectrographs;
- Spectroscopic Analysis;
- Composite Functions;
- Computerized Simulation;
- Luminosity;
- Magnitude;
- Morphology;
- Red Shift;
- Astronomy