The MASSIVE Survey - V. Spatially resolved stellar angular momentum, velocity dispersion, and higher moments of the 41 most massive local early-type galaxies

Abstract

We present spatially resolved two-dimensional stellar kinematics for the 41 most massive early-type galaxies (ETGs; M-K less than or similar to-25.7 mag, stellar mass M* greater than or similar to 10(11.8) M-circle dot) of the volumelimited (D < 108 Mpc) MASSIVE survey. For each galaxy, we obtain high-quality spectra in the wavelength range of 3650-5850 angstrom frome 246-fibre Mitchell integral-field spectrograph at McDonald Observatory, covering a 107 arcsecx107 arcsec field of view(often reaching 2 to 3 effective radii). We measure the 2D spatial distribution of each galaxy’s angular momentum (lambda and fast or slow rotator status), velocity dispersion (sigma), and higher order non-Gaussian velocity features (Gauss-Hermite moments h(3) to h(6)). Our sample contains a high fraction (similar to 80 per cent) of slow and non-rotators with lambda less than or similar to 0.2. When combined with the lower mass ETGs in the ATLAS(3D) survey, we find the fraction of slow rotators to increase dramatically with galaxy mass, reaching similar to 50 per cent at M-K similar to -25.5 mag and similar to 90 per cent at M-K less than or similar to -26 mag. All of our fast rotators show a clear anticorrelation between h(3) and V/sigma, and the slope of the anticorrelation is steeper in more round galaxies. The radial profiles of sigma show a clear luminosity and environmental dependence: the 12 most luminous galaxies in our sample (MK less than or similar to -26 mag) are all brightest cluster/group galaxies (except NGC 4874) and all have rising or nearly flat sigma profiles, whereas five of the seven ‘isolated’ galaxies are all fainter than M-K less than or similar to -25.8 mag and have falling sigma. All of our galaxies have positive average h(4); the most luminous galaxies have average h(4) similar to 0.05, while less luminous galaxies have a range of values between 0 and 0.05. Most of our galaxies show positive radial gradients in h(4), and those galaxies also tend to have rising sigma profiles. We discuss the implications for the relationship among dynamical mass, sigma , h(4), and velocity anisotropy for these massive galaxies.