Physics
Scientific paper
Jun 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997phdt........10t&link_type=abstract
Thesis (PHD). RUTGERS THE STATE UNIVERSITY OF NEW JERSEY - NEW BRUNSWICK , Source DAI-B 57/12, p. 7571, Jun 1997, 122 pages.
Physics
Dark Matter, M87, Ngc 3384, Ellipticals, Triaxials
Scientific paper
We present several data-based studies of the dynamics and morphology of early-type galaxies, with an emphasis on the distribution of dark matter. In the first study (Chapter 2), we attempt to map the distribution of dark matter around the giant elliptical galaxy M87 using the velocities of 43 globular clusters reported by Mould et al. (AJ, 99, 1823 (1990)). Assuming spherical symmetry in configuration and velocity space, we find a most likely, power-law dependence of dark matter density on radius of p(r) ∝ r-1.8, where the exponent lies between 0.2 and 3.0 with 99% confidence. We estimate that a sample of roughly 200 velocities would be required to determine the mass-density exponent to a precision of ±0.5. In the second part of the thesis (Chapters 3 and 4), we present the results of a study of the galaxy pair NGC 3384 (SB0)/NGC 3379 (E1) in the Leo I group using the Rutgers Fabry-Perot interferometer. We measured the velocities of 148 planetary nebulae around the two galaxies from the Doppler-shifted (OIII) emission line. The planetary nebula system in NGC 3384 exhibits an orderly rotation field aligned with the photometric axes of the galaxy. The mass of NGC 3384 is infered to be 1.6 x 1011 M&sun; within our last data point at 13 kpc. In the case of NGC 3379, no significant rotation of the planetary nebula system was detected. The mass of NGC 3379 is estimated to be 3 x 1011 M&sun; within 9 kpc, assuming a spherical, isotropic distribution of nebulae. The third part of the thesis (Chapters 5 and 6) consists of a fully nonparametric study of the distribution of elliptical galaxy intrinsic shapes. If elliptical galaxies of all intrinsic luminosities are considered as a single group, the frequency function of intrinsic shapes is found to be inconsistent with the axisymmetric hypothesis at the 99% level. However, many triaxial shape distributions can be found that reproduce the data. If elliptical galaxies are segregated according to intrinsic luminosity, we find a striking change in the shape distribution near MB = -20. Bright ellipticals have a narrow range of apparent shapes, centered around E2, while faint ellipticals exhibit a much broader shape distribution. The faint-galaxy data are consistent with the axisymmetric hypothesis, while the bright-galaxy data can only be explained via a triaxial shape distribution.
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