Brendon J. Brewer, Aaron A. Dutton, Tommaso Treu, Matthew W. Auger, Philip J. Marshall, Matteo Barnabè, Adam S. Bolton, David C. Koo, Léon V. E. Koopmans
We present gravitational lens models for 20 strong gravitational lens systems
observed as part of the Sloan WFC Edge-on Late-type Lens Survey (SWELLS)
project. Fifteen of the lenses are taken from paper I while five are newly
discovered systems. The systems are galaxy-galaxy lenses where the foreground
deflector has an inclined disc, with a wide range of morphological types, from
late-type spiral to lenticular. For each system, we compare the total mass
inside the critical curve inferred from gravitational lens modelling to the
stellar mass inferred from stellar population synthesis (SPS) models, computing
the stellar mass fraction within the critical curve. We find that, for the
lower mass SWELLS systems, adoption of a Salpeter stellar initial mass function
(IMF) leads to estimates of the stellar mass fraction that exceed 1. This is
unphysical, and provides strong evidence against the Salpeter IMF being valid
for these systems. Taking the lower mass end of the SWELLS sample (lensing
velocity dispersion less than 230 km/s), we find that the IMF is lighter (in
terms of stellar mass-to-light ratio) than Salpeter with 98% probability, and
consistent with the Chabrier IMF. This result is consistent with previous
studies of spiral galaxies based on independent techniques. In combination with
the heavier IMF inferred from the lensing and dynamical analysis of more
massive early-type lens galaxies from the SLACS sample, this result provides
strong evidence against a universal stellar IMF.
View original:
http://arxiv.org/abs/1201.1677
No comments:
Post a Comment