THE SL2S GALAXY-SCALE LENS SAMPLE. V. DARK MATTER HALOS AND STELLAR IMF OF MASSIVE EARLY-TYPE GALAXIES OUT TO REDSHIFT 0.8

• Published in: The Astrophysical journal 2015-02, Vol.800 (2), p.94
• Main Authors: Sonnenfeld, Alessandro, Treu, Tommaso, Marshall, Philip J., Suyu, Sherry H., Gavazzi, Raphaël, Auger, Matthew W., Nipoti, Carlo
• Format: Article
• Language: English
• Subjects: ASTRONOMY AND ASTROPHYSICS; cD; galaxies: elliptical and lenticular; galaxies: evolution; gravitational lensing: strong; Sciences of the Universe
• ISSN: 1538-4357; 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/800/2/94

We investigate the cosmic evolution of the internal structure of massive early-type galaxies over half of the age of the universe. We perform a joint lensing and stellar dynamics analysis of a sample of 81 strong lenses from the Strong Lensing Legacy Survey and Sloan ACS Lens Survey and combine the results with a hierarchical Bayesian inference method to measure the distribution of dark matter mass and stellar initial mass function (IMF) across the population of massive early-type galaxies. Lensing selection effects are taken into account. We find that the dark matter mass projected within the inner 5 kpc increases for increasing redshift, decreases for increasing stellar mass density, but is roughly constant along the evolutionary tracks of early-type galaxies. The average dark matter slope is consistent with that of a Navarro-Frenk-White profile, but is not well constrained. The stellar IMF normalization is close to a Salpeter IMF at log M * = 11.5 and scales strongly with increasing stellar mass. No dependence of the IMF on redshift or stellar mass density is detected. The anti-correlation between dark matter mass and stellar mass density supports the idea of mergers being more frequent in more massive dark matter halos.