Computer Science
Scientific paper
Jan 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt.........8f&link_type=abstract
PhD Dissertation, California Univ. Santa Cruz, CA United States
Computer Science
1
Galactic Rotation, Elliptical Galaxies, Spiral Galaxies, Galactic Clusters, Galactic Radiation, Emission Spectra, Line Spectra, Stellar Rotation, Populations, Velocity Distribution, Metallic Stars, Disk Galaxies
Scientific paper
Major and minor axes kinematic and line-strength profiles were derived for a sample of 13 brightest cluster galaxies (BCG's) and 15 S0 galaxies. Rotation curves and velocity dispersion profiles were determined in order to study the internal stellar kinematics of the galaxies and investigate their relationship to ellipticals. Line-strengths and their gradients in Mg, Fe, and H-beta were measured to study the stellar populations of the objects in our sample and make comparisons across the spectrum of early-type galaxies. In our kinematic study of 13 brightest cluster galaxies the primary conclusions were that while the velocity dispersion profiles of BCG's are similar to those of ellipticals, the amount of rotation in BCG's is significantly lower. The main results from our investigation of BCG line-strengths were that BCG's follow the same relationship between central Mgb line-strength and central velocity dispersion found for ellipticals. Brightest cluster galaxy magnesium to iron ratios are similar to the behavior of luminous ellipticals in being larger than the (Mg/Fe) ratios found in the most metal-rich stars in the solar neighborhood. The metal line-strength gradients of BCG's are similar to those found in normal bright ellipticals. The most significant difference between BCG's and ellipticals is that BCG's have lower H-beta line-strengths and thus, older inferred ages than bright ellipticals. The results from our study of the kinematics of 15 S0 galaxies show that the disks of S0's are kinematically-cold, sigmadisk approximately equal to 60 km/s, have approximately constant velocity dispersion to the limit of our measurements, and are rapid rotators. A variety of detailed structures are found in the stellar rotation curves and velocity dispersion profiles of the individual objects suggesting that complex formation and evolutionary mechanisms have occurred. We find that although there is significant scatter, S0 galaxies roughly follow the same relationship between central Mgb line-strength and central velocity dispersion found for ellipticals. The H-beta line-strengths of the objects in our sample span a range of values which indicates that age differences exist among the galaxies. The H-beta index values within individual galaxies are fairly constant with radius and indicate that the centers of S0 galaxies are younger by 1-3 Gyr than the outer regions. The centers of the S0 galaxies are uniformly metal-rich with respect to the disks and outer bulge regions. The S0 disks display constant line-strength indicating that they have uniform age and metallicity throughout.
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