Dynamics in Elliptical Galaxies

Dynamics in Elliptical Galaxies - Dynamics in Elliptical...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Dynamics in Elliptical Galaxies For decades it was considered obvious beyond the need for observations that elliptical galaxies were oblate objects, rotationally flattened. The observations to actually check this were quite difficult, since ellipticals don't have convenient numbers of H II regions, but revealed that most ellipticals rotate far too slowly for their apparent shapes - the shape must be an intrinsic property of the stars' velocity distribution (see Davies et al. 1983 ApJ 266, 41). An important discriminant is the ratio v/ σs of rotation velocity to (line-of-sight) velocity dispersion. For a given shape of potential, v/ σ predicts flattening ε. Elliptical galaxies mostly ignore this prediction, leading to the notion that their shapes are triaxial ellipsoids supported not by rotation, but by anisotropy in the velocity distribution of the stars. This is shown in Fig. 3 of Davies et al. (shown courtesy of the AAS): To model these galaxies in detail, one must consider statistical mechanics of available kinds of orbits (tube, box. ..) and their stability - see Binney and Tremaine ch. 2-5). In general, one expects orbits in such a family (in either physical or phase space) to obey the
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 3

Dynamics in Elliptical Galaxies - Dynamics in Elliptical...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online