ROSAT PSPC Observations of Two Low Luminosity Early-Type Galaxies
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Session 42 -- Ellipticals
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[42.02] ROSAT PSPC Observations of Two Low Luminosity Early-Type Galaxies

Michael Loewenstein (NASA/GSFC and USRA), Robert Petre (NASA/GSFC)

The x-ray spectra of early-type galaxies are composites of discrete source and diffuse hot gas components. While the emission from the most luminous galaxies is dominated by hot gas, simple scaling and binding mass arguments predict that discrete sources should become important below some transition optical luminosity. If early-type galaxies have massive halos comprising 90\% of their mass and the best observational estimate of the Type Ia supernova rate, this transition luminosity should be at $L_B\sim 3\ 10^{10}L_{\sun}$. We present ROSAT PSPC observations of two early-type galaxies, NGC 3607 and NGC 4697, with luminosites near this transition. We discuss the spectral and spatial evidence for discrete source emission, and the resulting implications for the luminosity-scaling of the supernova rate and dark matter in early-type galaxies.

Thursday program listing