The bulge-halo conspiracy in massive elliptical galaxies: implications for the stellar initial mass function and halo response to baryonic processes

Understand

Recent studies have shown that massive elliptical galaxies have total mass density profiles within an effective radius that can be approximated as \rho_{tot}\propto r^{-\gamma'}, with mean slope <\gamma'>=2.08 \pm 0.03 and scatter \sigma_\gamma'=0.16 \pm 0.02.

• The small scatter of the slope (known as the bulge-halo conspiracy) is not generic in LCDM based models and therefore contains information about the galaxy formation process.
• We compute the distribution of \gamma' for LCDM-based models that reproduce the observed correlations between stellar mass, velocity dispersion, and effective radius of early-type galaxies in the SDSS.
• The models have a range of stellar initial mass functions (IMFs) and dark halo responses to galaxy formation.