The MASSIVE Survey - VII. The relationship of angular momentum, stellar mass and environment of early-type galaxies
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2017 The Authors. We analyse the environmental properties of 370 local early-type galaxies (ETGs) in theMASSIVE and ATLAS3D surveys, two complementary volume-limited integral-field spectroscopic (IFS) galaxy surveys spanning absolute K-band magnitude -21.5 MK -26.6, or stellar mass 8 109 M* 2 1012M. We find these galaxies to reside in a diverse range of environments measured by four methods: group membership (whether a galaxy is a brightest group/cluster galaxy, satellite or isolated), halo mass, large-scale mass density (measured over a fewMpc) and local mass density (measured within the Nth neighbour). The spatially resolved IFS stellar kinematics provide robust measurements of the spin parameter e and enable us to examine the relationship among e, M* and galaxy environment. We find a strong correlation between e and M*, where the average e decreases from ~0.4 to below 0.1 with increasing mass, and the fraction of slow rotators fslow increase from ~10 to 90 per cent. We show for the first time that at fixed M*, there are almost no trends between galaxy spin and environment; the apparent kinematic morphology-density relation for ETGs is therefore primarily driven by M* and is accounted for by the joint correlations between M* and spin, and between M* and environment. A possible exception is that the increased fslow at high local density is slightly more than expected based only on these joint correlations. Our results suggest that the physical processes responsible for building up the present-day stellar masses of massive galaxies are also very efficient at reducing their spin, in any environment.
