SIMBAD references

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 2.0x10¹⁰ to 3.4x10¹¹M_☉ 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 ε(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.