Samenvatting
We present a detailed two-dimensional stellar dynamical analysis of a
sample of 44 cosmological hydrodynamical simulations of individual
central galaxies with stellar masses of 2 × 1010
M⊙ ≲ M* ≲ 6 × 1011
M⊙. 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 disc 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 (≳18
per cent) in situ formation of stars since z ≈ 2, or with additional
gas-rich major mergers - resulting in a spin-up - in their formation
history, form elongated (ɛ ˜ 0.45) fast rotators
(λR ˜ 0.46) with a clear anticorrelation 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 (λR ˜ 0.43). This formation path does
not result in anticorrelated h3 and v/σ. The formation
histories of slow rotators can include late major mergers. If the merger
is gas rich, the remnant typically is a less flattened slow rotator with
a central dip in the velocity dispersion. If the merger is gas poor, the
remnant is very elongated (ɛ ˜ 0.43) and slowly rotating
(λR ˜ 0.11). 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. We discuss general implications for the
formation of fast and slowly rotating galaxies as well as the weaknesses
and strengths of the underlying models.
Originele taal-2 | English |
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Pagina's (van-tot) | 3357-3387 |
Aantal pagina's | 31 |
Tijdschrift | Monthly Notices of the Royal Astronomical Society |
Volume | 444 |
DOI's | |
Status | Published - nov.-2014 |