DETECTIONS OF HARD X-RAY EMISSIONS FROM BRIGHT EARLY-TYPE GALAXIES WITH ASCA

Five bright elliptical galaxies in the Virgo Cluster, NGC 4365, NGC 43 74 (M84), NGC 4406 (M86), NGC 4472 (M49), and NGC 4636, were observed with ASCA. In addition to the extended thermal X-ray emission of tempe rature kT similar to 1 keV, harder X-rays with color temperature kT gr eater than or equal to 2 keV were detected from all of them. The 2-10 keV luminosities of this hard component for the five galaxies, integra ted within 5', are distributed within a relatively narrow range of (1- 4) x 10(40) ergs s(-1). The hard X-ray component is primarily attribut ed to the integrated emission from discrete X-ray sources. In NGC 4406 and NGC 4374 the data indicate that the hard component is contributed additionally by foreground/background emission from the hot intraclus ter medium (ICM) of the Virgo Cluster. The hard component of NGC 4472 seems also contributed by the Virgo ICM emission, but in this case the re is evidence that the ICM brightness is locally enhanced within simi lar to 10' of NGC 4472.