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Session 49 - Elliptical Galaxies & Bulges.
Display session, Thursday, January 08
Exhibit Hall,
We observed the faint S0 galaxy NGC 1380 using the ROSAT PSPC for 13 ksec and the ROSAT HRI for 42.5 ksec. We show here that the PSPC spectrum can be modeled as a thermal spectrum with kT \sim0.5 keV which is consistent with emission from a hot ISM. We do not detect any emission from a hard component, in contrast to the prediction for a low luminosity E/S0 galaxy. The radial profiles from the PSPC and HRI data support the spectral fitting because each profile is more sharply concentrated than the optical light (which reflects the stellar distribution) in contrast to other E/S0 galaxies. The PSPC radial profile is consistent with emission from a point source, while the HRI profile reveals the presence of extended hot gas. The difference is attributed to the larger FWHM of the point spread function of the PSPC. We also extend the L_X-- L_B plane, as described by Matsumoto et al. (1997) in the range 10.8 < log L_B < 11.3, to log L_B \sim10.5. We extend this plane separately for the hard discrete and the soft thermal components and show that the scaling relation for the hard component continues to at least log L_B \sim10.5.
