Expected intermediate-mass black holes in the Virgo cluster - I. Early-type galaxies

We expand upon the AMUSE-Virgo survey which imaged 100 early-type Virgo cluster galaxies with the Chandra X ray Observatory, and we place an emphasis on potential intermediate-mass black holes (IMBHs). Virgo early-type galaxies with absolute magnitudes m(B) greater than or similar to -20.5 mag have B-band luminosities that scale with the square of the stellar velocity dispersion: LB proportional to sigma(2). We show that the non-linear 'super-quadratic' relation M-bh proportional to L-B(2) - L-B(2.5) from Graham & Scott yields black hole masses, M-bh, that agree with the M-bh-sigma relation down to at least M-bh = 10(4) M-circle dot. We predict that 30 of the 100 galaxies have M-bh <= 10(5) M-circle dot, with IC 3602 having M-bh = 10(4) M-circle dot and IC 3633 having M-bh = (6-8)x 10(3) M-circle dot. We additionally revise the black hole Eddington ratios, and their scaling with black hole mass, and we report a pointlike Chandra source at the nucleus of five additional galaxies (NGC 4382, NGC 4387, NGC 4417, NGC 4467, and NGC 4472). Moreover, three of the galaxies predicted here to host an IMBH have a point-like Chandra source near their nucleus: IC 3442 (M-bh = 2 x 10(5) M-circle dot); IC 3492 (M-bh = 5 x 10(4 )M(circle dot)); and IC 3292 (M-bh = 6 x 10(4 )M(circle dot)). Furthermore, IC 3442 and IC 3292 host a nuclear star cluster that is expected to house an 'MBE Finally, we present the (B - K)-m(K) colour-magnitude diagram and discuss the implications for the M-bh-LK and M-bh - M-*,M-galaxy relations, revealing why stripped galaxies, especially rare compact elliptical galaxies, should be excluded from M-bh-L scaling relations.