1610.07605
The inner structure of early-type galaxies in the Illustris simulation
Xu, Sprintel, Sluse, et al
Early-type galaxies provide unique tests for the predictions of the CDM cosmology and the baryonic physics assumptions entering models for galaxy formation. In this work, use the Illustris sim to study correlations of 3 main properties of early-type galaxies, namely, the stellar orbital anisotropies, the central dark matter fractions and the central radial density slopes, as well as their redshift evolution since z=1.0. Find that lower-mass galaxies or galaxies at higher redshift tend to be bluer in rest-frame colour, have higher central gas fractions, and feature more tangentially anisotropic orbits and steeper central density slopes than their higher-mass or lower-z counterparts, respectively. The projected central DM fraction within the effective radius shows no significant mass dependence but positively correlates with galaxy effective radii due to the aperture effect. The central density slopes obtained in the simulation by combining SL measurements with single aperture kinematics are found to be shallower than the true density slopes. Identify systematic biases in this measurement due to 2 common modelling assumptions, isotropic stellar orbital distributions and power-law density profiles. Also compare the properties of early-type galaxies in Illustris to those from the SLACS, SL2S and BOSS surveys, ending in general broad agreement but also some tension, which appears to be mostly caused by too large galaxy sizes in Illustris.
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