The ATLAS3D project - XXV: Two-dimensional kinematic analysis of simulated galaxies and the cosmological origin of fast and slow rotators
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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)
Naab , T , Oser , L , Emsellem , E , Cappellari , M , Krajnovic , D , McDermid , R M , Alatalo , K , Bayet , E , Blitz , L , Bois , M , Bournaud , F , Bureau , M , Crocker , A , Davies , R L , Davis , T A , de Zeeuw , P T , Duc , P-A , Hirschmann , M , Johansson , P H , Khochfar , S , Kuntschner , H , Morganti , R , Oosterloo , T , Sarzi , M , Scott , N , Serra , P , van de Ven , G , Weijmans , A & Young , L M 2014 , ' The ATLAS 3D project - XXV: Two-dimensional kinematic analysis of simulated galaxies and the cosmological origin of fast and slow rotators ' Monthly Notices of the Royal Astronomical Society , vol 444 , no. 4 , pp. 3357-3387 . DOI: 10.1093/mnras/stt1919
Monthly Notices of the Royal Astronomical Society
© 2014. The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society
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