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Session 90 - OJ287 and X-Ray Emission from Elliptical Galaxies.
Oral session, Wednesday, January 15
Harbour B,

[90.04] The X-ray Morphology of Elliptical Galaxies

P. C. Hanlan, J. N. Bregman (U. Michigan)

The hot interstellar medium found in most elliptical galaxies can offer a new window into the understanding of the dynamics of these objects. Using both low and high angular resolution X-ray data from ROSAT, the behavior of the hot gas can be examined from the centers to the outer regions of these objects. Because of the low photon counts found in most ROSAT observations, we have developed extensive optimization and Monte Carlo simulation techniques to define the shape and the corresponding uncertanties of the isophotes of diffuse X-ray sources.

If cooling gas is flowing towards the center of an elliptical galaxy and if angular momentum is conserved, disks of X-ray emitting material should form that will cause a flattening in the observed X-ray isophotes of the galaxy as one looks towards the center. However, we find that the predicted flattening does not, in general, occur. This implies that there might be transfer of angular momentum or turbulence in the hot gas in elliptical galaxies.

Being able to quantify the morphology of the X-ray isophotes in elliptical galaxies is useful in other applications. Comparing the shape of the X-ray and optical isophotes in the centers of galaxies can help determine the anisotropy of the stellar velocity dispersion. In the outer parts of elliptical galaxies, we use the X-ray emission to trace the shape of the dark matter.

Program listing for Wednesday