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

Understand

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 $\mathfrak{M}_B\gtrsim-20.5$ mag have $B$-band luminosities that scale with the square of the stellar velocity dispersion: $L_B\propto\sigma^2$.
• We show that the non-linear `super-quadratic' relation $M_{\rm bh}\propto L_B^2$-$L_B^{2.5}$ from Graham & Scott yields black hole masses, $M_{\rm bh}$, that agree with the $M_{\rm bh}$-$\sigma$ relation down to at least $M_{\rm bh}=10^4\,M_{\odot}$.
• We predict that 30 of the 100 galaxies have $M_{\rm bh}\le10^5\,M_{\odot}$, with IC3602 having $M_{\rm bh}=10^4\,M_{\odot}$ and IC3633 having $M_{\rm bh}=$(6-8)$\times10^3\,M_{\odot}$.