The ATLAS3D project - XXV: Two-dimensional kinematic analysis of simulated galaxies and the cosmological origin of fast and slow rotators

T. Naab, L. Oser, E. Emsellem, M. Cappellari, D. Krajnovic, R. M. McDermid, K. Alatalo, E. Bayet, L. Blitz, M. Bois, F. Bournaud, M. Bureau, A. Crocker, R. L. Davies, T. A. Davis, P. T. de Zeeuw, P.-A. Duc, M. Hirschmann, P. H. Johansson, S. KhochfarH. Kuntschner, R. Morganti, T. Oosterloo, M. Sarzi, N. Scott, P. Serra, G. van de Ven, A. Weijmans, L. M. Young

Research output: Contribution to journalArticlepeer-review

265 Citations (Scopus)

Abstract

We present a detailed two-dimensional stellar dynamical analysis of as ample of 44 cosmological hydrodynamical simulations of individual central galaxies with stellar masses of 2 x 1010Msun ∼≤ Mstar ∼≤ 6x 1011Msun. Kinematic maps of the stellar line-of-sight velocity, velocity dispersion, and higher-order Gauss-Hermite moments h3 and h4 are constructed for each central galaxy and for the most massive satellites. The amount of rotation is quantified using the λR-parameter. The velocity, velocity dispersion, h3, and h4 fields of the simulated galaxies show a diversity similar to observed kinematic maps of early-type galaxies in the ATLAS3D survey. This includes fast (regular), slow, and misaligned rotation, hot spheroids with embedded cold disk components as well as galaxies with counter-rotating cores or central depressions in the velocity dispersion. We link the present-day kinematic properties to the individual cosmological formation histories of the galaxies. In general, major galaxy mergers have a significant influence on the rotation properties resulting in both a spin-down as well as a spin-up of the merger remnant. Lower mass galaxies with significant in-situ formation of stars, or with additional gas-rich major mergers - resulting in a spin-up - in their formation history, form elongated fast rotators with a clear anti-correlation of h3 and v/σ. An additional formation path for fast rotators includes gas-poor major mergers leading to a spin-up of the remnants. This formation path does not result in anti-correlated h3 and v/σ. The galaxies most consistent with the rare class of non-rotating round early-type galaxies grow by gas-poor minor mergers alone. In general, more massive galaxies have less in-situ star formation since z ∼ 2, rotate slower and have older stellar populations. (shortened)

Original languageEnglish
Pages (from-to)3357-3387
JournalMonthly Notices of the Royal Astronomical Society
Volume444
Issue number4
Early online date17 Sept 2014
DOIs
Publication statusPublished - 11 Nov 2014

Keywords

  • ISM: clouds
  • ISM: kinematics and dynamics
  • Stars: formation

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