Supermassive Black Holes and Nuclear Star Clusters: Connection with the Host Galaxy Kinematics and Color

A. V. Zasov, A. M. Cherepashchuk

Published 2013-12-16Version 1

We consider the relationship between the masses of the central objects in disky galaxies - supermassive black holes (SMBHs) and nuclear star clusters (NCs) - and various parameters of parent galaxies: velocity of rotation $V_{(2)}$ at $R= 2$ kpc, maximal velocity of rotation $V_{\textrm{max}}$, the indicative dynamical mass $M_{25}$, the total mass of the stellar population $M_{*}$, and the total color index ($B{-}V$). The mass of nuclear clusters $M_{\rm nc}$ correlates more closely with the kinematic parameters and total mass of galaxies than the mass of central black holes $M_{\rm bh}$, including correlation with the velocity $V_{\textrm{max}}$, which characterizes the virial mass of the dark halo. On average, lenticular galaxies are distinguished by higher masses $M_{\rm bh}$ compared to other types of galaxies with similar characteristics. The dependence of masses of central objects on the color index is bimodal: galaxies of the red group (red-sequence), which have ($B{-}V) > 0.6{-}0.7$, being mostly early-type galaxies, differ from bluer galaxies, by higher values of $M_{\rm nc}$ and $M_{\rm bh}$. The red-group galaxies have systematically higher $M_{\rm bh}$ values, even when the host-galaxy parameters are similar. In contrast, in the case of nuclear stellar clusters, the "blue" and "red" galaxies form unified sequences at the diagrams. The results agree with scenarios in which most red-group galaxies form as a result of the partial or complete loss of interstellar gas in a stage of high nuclear activity in galaxies whose central black-hole mass exceeds $10^6 {-} 10^7 M_{\odot}$ (depending on the total mass of a galaxy). Most of galaxies with $M_{\rm bh}> 10^7 M_{\odot}$ are lenticular galaxies (types S0, E/S0), whose disks are usually devoid of gas.