Bibcode
Wu, Xufen; Gerhard, Ortwin; Naab, Thorsten; Oser, Ludwig; Martinez-Valpuesta, I.; Hilz, Michael; Churazov, Eugene; Lyskova, Natalya
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 438, Issue 3, p.2701-2715
Fecha de publicación:
3
2014
Número de citas
78
Número de citas referidas
67
Descripción
We study the dark and luminous mass distributions, circular velocity
curves (CVCs), line-of-sight kinematics and angular momenta for a sample
of 42 cosmological zoom simulations of galaxies with stellar masses from
2.0 × 1010 to 3.4 × 1011
M⊙ h-1. Using a temporal smoothing technique,
we are able to reach large radii. We find the following. The dark matter
halo density profiles outside a few kpc follow simple power-law models,
with flat dark matter CVCs for lower mass systems, and rising CVCs for
high-mass haloes. The projected stellar density distributions at large
radii can be fitted by Sérsic functions with n ≳ 10, larger
than for typical early-type galaxies (ETGs).The massive systems have nearly flat total (luminous
plus dark matter) CVCs at large radii, while the less massive systems
have mildly decreasing CVCs. The slope of the circular velocity at large
radii correlates with circular velocity itself.The dark matter fractions within the projected stellar
half-mass radius Re are in the range 15-30 per cent and
increase to 40-65 per cent at 5Re. Larger and more massive
galaxies have higher dark matter fractions. The fractions and trends
with mass and size are in agreement with observational estimates, even
though the stellar-to-total mass ratio is ˜2-3 times higher than
estimated for ETGs.The short axes of
simulated galaxies and their host dark matter haloes are well aligned
and their short-to-long axis ratios are correlated.The stellar root mean square velocity
vrms(R) profiles are slowly declining, in agreement with
planetary nebulae observations in the outer haloes of most
ETGs.The line-of-sight velocity
fields {bar{v}} show that rotation properties at small and large radii
are correlated. Most radial profiles for the cumulative specific angular
momentum parameter λ(R) are nearly flat or slightly rising, with
values in [0.06, 0.75] from 2Re to 5Re. A few
cases show local maxima in |{bar{v}}|/σ (R). These properties
agree with observations of ETGs at large radii.Stellar mass, ellipticity at large radii
ɛ(5Re) and λ(5Re) are correlated:
the more massive systems have less angular momentum and are rounder, as
for observed ETGs.More massive
galaxies with a large fraction of accreted stars have radially
anisotropic velocity distributions outside Re. Tangential
anisotropy is seen only for galaxies with high fraction of in situ
stars.
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