Chandra observation of low-mass X-ray binaries in the elliptical galaxy M84

We present characteristics of the X-ray point-source population in the M84 galaxy observed by the Chandra Advanced CCD Imaging Spectrometer S-Array. We find an excess in the number of sources centered on M84 with a spatial distribution closely corresponding to the M84 stellar light. Given an absence of recent star formation, accreting binaries are the only candidates for the M84 X-ray sources. The majority of M84 sources (with luminosities exceeding 10(38) ergs s(-1)) exhibit hardness ratios expected from multi-temperature blackbody disk emission. The most luminous sources, which we attribute to accreting black holes, exhibit X-ray colors typical of a blackbody spectrum. We also identify the sources whose X-ray colors match the expectations for constituents of the cosmic X-ray background. The number of such sources agrees with that expected to be background sources. After correcting for incompleteness in the source detection, we find a log N-log S for M84 similar to that of the elliptical galaxy NGC 4697, i.e., having a break at a luminosity of L-b = 2.4(-0.3)(+0.6) x 10(38) ergs s(-1), approximately the Eddington limit on the isotropic luminosity for accretion onto a neutron star. The slope of the luminosity function above the break provides evidence for a mass distribution in the M84 accreting black holes.