Galaxy evolution in dense clusters

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6821426

Newberry, M V

In order to substantiate the observation that the fraction of blue galaxies in the cores of dense clusters increases with redshift (the Butcher-Oemler effect), spectra were obtained for 61 galaxies in 7 dense clusters over the redshift range 0.195 < z < 0.38. The majority of the red galaxies are cluster members whereas only 6 of 13 blue galaxies belong to the clusters to which they were assigned by Butcher and Oemler on the basis of broadband photometry. A t-test indicates that the blue galaxy fractions of the high- and low-redshift clusters are significantly different at better than the 99.5% confidence level. Further, a regression is significant at the 97.5% confidence level. Based upon these data, the Butcher-Oemler effect is verified. Models for the evolution of the integrated spectra of stellar populations were constructed in order to ascertain the nature of the stellar populations within the observed galaxies. These models included the effects of asymptotic giant-branch and horizontal-branch evolution, were metal rich, and predicted spectral features as weak as approx. 1A. The stellar population models developed here were used to produced such models to re-evaluate their conclusion.

• Research Organization: Michigan Univ., Ann Arbor (USA)
• OSTI ID: 6821426
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics &amp; Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DATA ANALYSIS
GALACTIC EVOLUTION
GALAXY CLUSTERS
MATHEMATICAL MODELS
RED SHIFT
SPECTRA
STAR EVOLUTION
STAR MODELS