HEAD 2000, November 2000
Session 15. Galaxies
Display, Tuesday, November 7, 2000, 8:00am-6:00pm, Bora Bora Ballroom

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[15.07] X-Ray Generation in Starburst Galaxies

M. Sipior, M. Eracleous (Penn State U.)

The various mechanisms by which starburst galaxies emit hard (2--10 keV) X-radiation are not yet thoroughly understood. This is particularly relevant in light of recent observations of starbursts and LINERs from the \emph{Chandra} X-Ray Observatory. As an example, the prototypical starburst galaxy M82 is shown to have a number of heretofore unresolved luminous structures, including several X-ray binary systems, and a diffuse nebulosity.

Our goal here is to model the various X-ray emission processes relevant to starbursts, and gauge their relative importance to the overall hard X-ray flux. Radiation from XRBs is calculated via population synthesis models, effectively giving an LX per O-type star. Starting with observations of the discrete emission in a starburst, we then work backwards to constrain the IMF of the starburst regions, addressing the issue of whether IMFs in starbursts are dramatically different than those found elsewhere.

We investigate whether the diffuse X-ray emission in a starburst arises from infrared photons upscattered upon interaction with a supernova-energized electron gas. The star-formation rate clearly influences the supernova rate, which in turn affects the energy distribution of the electron fluid. As well, the SFR correlates with the ambient infrared flux, the seed photons promoted to X-ray energies via an inverse Compton interaction. We are in the process of constructing an IC code which will allow more meaningful comparisons between infrared and X-ray maps of starburst galaxies. The code evolves an infrared photon field through Compton interaction with electron clouds of various geometries. This should greatly aid in the understanding of the diffuse X-ray component observed by \emph{Chandra}, both in terms of spectral shape and the overall flux seen.

The author(s) of this abstract have provided an email address for comments about the abstract: sipior@astro.psu.edu

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