Stellar collisions in galactic centres: black hole growth and colour gradients

作者：Yu QJ^*

来源：Monthly Notices of the Royal Astronomical Society, 2003, 339(1): 189-211.

DOI：10.1046/j.1365-8711.2003.06156.x

• black hole physics
• blue stragglers
• galaxies : individual : M31
• galaxies : individual : M32
• galaxies : kinematics and dynamics
• galaxies : photometry

We study the effects of stellar collisions, particularly on feeding massive black holes (BHs) and colour gradients, in realistic galactic centres. We find that the mass released by stellar collisions is not sufficient to account for the present BH mass in galactic centres, especially in bright galaxies. This study, together with the study by Magorrian & Tremaine on tidal disruption of stars by massive BHs, implies that the material for BH growth (especially in galaxies brighter than similar to10(9) L-.) can only come from other sources, for example, the mass released by stellar evolution in the initial similar to1 Gyr of the lifetime of the galaxy, or the gas that sinks to the galactic centre in a galaxy merger. We also analyse how the colour of a stellar system is affected by collisions of stars. We find that collisions between main-sequence stars cannot cause observable colour gradients in the visible bands at projected radius R greater than or similar to 0.1 arcsec in M31, M32 and other nearby galactic centres. This result is consistent with the lack of an observable colour gradient in M32 at R greater than or similar to 0.1 arcsec. At even smaller radii, the colour differences caused by collisions between main-sequence stars are at most 0.08 mag at R = 0.02 arcsec. The averaged bluing caused by stellar collisions in the region R < 0.1 arcsec of M32 should not be larger than 0.06 mag in colour index U -V and 0.02 mag in V -I . The observed bluing in the centre of the galaxy M31 (in a 0.14 x 0.14 arcsec(2) box) must be caused by some mechanism other than collisions between main-sequence stars.

• 出版日期2003-2-11