Early-type galaxy core phase densities

Abstract

Early-type galaxies have projected central density brightness profile logarithmic slopes, γ′, ranging from about 0 to 1. We show that γ′ is strongly correlated, r = 0.83, with the coarse grain phase density of the galaxy core, Q 0 ≡ ρ/σ3. The luminosity-γ′ correlation is much weaker, r = -0.51. Q 0 also serves to separate the distribution of steep core profiles, γ′ > 0.5, from shallow profiles, γ′ < 0.3, although there are many galaxies of intermediate slope, at intermediate Q 0, in a volume-limited sample. The transition phase density separating the two profile types is approximately 0.003 M⊙ pc-3 km-3 s3, which is also where the relation between Q 0 and core mass shows a change in slope, the rotation rate of the central part of the galaxy increases, and the ratio of the black hole to core mass increases. These relations are considered relative to the globular cluster inspiral core buildup and binary black hole core scouring mechanisms for core creation and evolution. Mass-enhanced globular cluster inspiral models have quantitative predictions that are supported by data, but no single model yet completely explains the correlations. © 2014. The American Astronomical Society. All rights reserved.