Ellipticals at $z=0$ from Self-Consistent Hydrodynamical Simulations: Comparison with SDSS Structural and Kinematical Data

Abstract

We present results of an analysis of the structural and kinematical properties of a sample of elliptical-like objects (ELOs) identified in four hydrodynamical, self-consistent simulations run with the DEVA code (Serna et al. 2003). Star formation has been implemented in the code through a simple phenomenological parameterization, that takes into account stellar physics processes only implicitly through the values of a threshold gas density, ${\rho }_{\mathrm{g},\mathrm{thres}}$, and an efficiency parameter, $c_{\ast }$. The four simulations operate in the context of a $\Lambda$CDM cosmological model consistent with observations, resolve ELO mass assembly at scales up to $\simeq$ 2 kpc, and differ in the values of their star formation parameters. Stellar masses, projected half-mass radii and central l.o.s. velocity dispersions, ${\sigma }_{\mathrm{los},0}$, have been measured on the ELO sample and their values compared with data from the Sloan digital sky survey. For the first time in self-consistent simulations, a good degree of agreement has been shown, including the Faber-Jackson and the $D_n-{\sigma }_{\mathrm{los},0}$ relations, among others, but only when particular values of the ${\rho }_{\mathrm{g},\mathrm{thres}}$ and $c_{\ast }$ parameters are used. This demostrates the effect that the star formation parameterization has on the ELO mass distribution. Additionally, our results suggest that it is not strictly necessary, at the scales resolved in this work, to appeal to energy sources other than gravitational (as for example supernovae feedback effects) to account for the structure and kinematics of large ellipticals.

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