Depleted cores, multicomponent fits, and structural parameter relations for luminous early-type galaxies

Abstract

New surface brightness profiles from 26 early-type galaxies with suspected partially depleted cores have been extracted from the full radial extent of Hubble Space Telescope images. We have carefully quantified the radial stellar distributions of the elliptical galaxies using the core- Sérsic model whereas for the lenticular galaxies a core-Sérsic bulge plus an exponential disc model gives the best representation. We additionally caution about the use of excessive multiple Sérsic functions for decomposing galaxies and compare with past fits in the literature. The structural parameters obtained from our fitted models are, in general, in good agreement with our initial study using radially limited (R ≲ 10 arcsec) profiles, and are used here to update several 'central' as well as 'global' galaxy scaling relations. We find near-linear relations between the break radius Rb and the spheroid luminosity L such that Rb ∝ L1.13±0.13, and with the supermassive black hole mass MBH such that Rb ∝ M0.83±0.21BH. This is internally consistent with the notion that major, dry mergers add the stellar and black hole mass in equal proportion, i.e. MBH ∝ L. In addition, we observe a linear relation Rb ∝ R0.98±0.15e for the core-Sérsic elliptical galaxies - where Re is the galaxies' effective half-light radii - which is collectively consistent with the approximately linear, bright-end of the curved L-Re relation. Finally, we measure accurate stellar mass deficits Mdef that are in general 0.5-4 MBH, and we identify two galaxies (NGC 1399, NGC 5061) that, due to their high Mdef/MBH ratio, may have experienced oscillatory core-passage by a (gravitational radiation)-kicked black hole. The galaxy scaling relations and stellar mass deficits favour core-Sérsic galaxy formation through a few 'dry' major merger events involving supermassive black holes such that Mdef ∝ M3.70±0.76BH, for MBH≳ 2 × 108M⊙.