摘要：

We have found compact X-ray sources in the center of 21 (54%) of 39 nearby face-on spiral and elliptical galaxies with available ROSAT HRI data. ROSAT X-ray luminosities (0.2-2.4 keV) of these compact X-ray sources are ~10-10ergs s(with a mean of 3×10ergs s). The mean displacement between the location of the compact X-ray source and the optical photometric center of the galaxy is ~390 pc. The fact that compact nuclear sources were found in nearly all (five of six) galaxies with previous evidence for a black hole or an active galactic nucleus (AGN) indicates that at least some of the X-ray sources are accreting supermassive black holes. ASCA spectra of six of the 21 galaxies show the presence of a hard component with relatively steep (Γ~2.5) spectral slope. A multicolor disk blackbody model fits the data from the spiral galaxies well, suggesting that the X-ray object in these galaxies may be similar to a black hole candidate in its soft (high) state. ASCA data from the elliptical galaxies indicate that hot (kT~0.7 keV) gas dominates the emission.From deep ROSAT PSPC and HRI observations of M86 (NGC 4406) we have mapped metal abundance and temperature changes across the image and detected significant structure in addition to the X-ray plume. We measure a high abundance in the plume of Z~0.65^+0.4_-0.2Z_solar, which is significantly higher than the abundance in the core of M86 (~0.3+/-0.1 Z_solar) or the cluster abundance (~0.2 Z_solar). The spectra from regions larger than the inner few arcmin show an enhanced silicon abundance. The galaxy and the plume are at similar temperatures kT~0.8+/-0.03 keV, compared to the cluster temperature of ~1.9 keV. The structures detected and the abundance measurements support the hypothesis that the Virgo ICM is ram-pressure stripping the ISM of M86 in a single blob. Dust in the stripped material, previously held within cold gas clouds, is being destroyed. The morphology and calculations of the ram pressure indicate that M86 may have a southwards velocity in the plane of the sky of ~500 km s^-1 compared to its radial velocity of 1374 km s^-1 relative to the cluster.

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