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S. Diehl, T.S. Statler (Ohio University)
We present results from a study of the X-ray emitting interstellar gas in normal elliptical galaxies, based on a reanalysis of archival Chandra ACIS data on ~ 70 objects. A new technique is developed to remove the contribution of unresolved point sources to the diffuse emission, after removing the resolved sources. This is done by dividing the data into appropriate hard and soft energy bands, correcting for exposure maps and background, and modeling the unresolved point source emission by a scaled version of the hard band image. The scale factor is derived by extrapolating the hardness ratio of resolved point sources to low luminosities. Subtracting this model from the soft band reveals the morphology of the hot gas alone. Fits to the gas surface brightness profiles and spectra provide the means to determine a fiducial surface density, length scale, and temperature, and thereby investigate the existence of a Fundamental Plane relation for elliptical galaxies purely in the X-ray regime. We also study the morphology of the hot gas, and present a "gas-only" gallery of normal ellipticals in the Chandra archive. The gas-only images are adaptively binned using a new algorithm based on a generalized Voronoi tessellation. Comparison of the optical and gas morphologies gives insight into the importance of rotational support and/or AGN-related processes for the hot gas. Either could have major consequences for dark halo mass estimates, which are mostly based on the common assumption of hydrostatic equilibrium.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.