Kavli Affiliate: Joshua Frieman
| First 5 Authors: Chin Yi Tan, Anowar J. Shajib, Simon Birrer, Alessandro Sonnenfeld, Tommaso Treu
| Summary:
The mass distribution in massive elliptical galaxies encodes their
evolutionary history, thus providing an avenue to constrain the baryonic
astrophysics in their evolution. The power-law assumption for the radial mass
profile in ellipticals has been sufficient to describe several observables to
the noise level, including strong lensing and stellar dynamics. In this paper,
we quantitatively constrained any deviation, or the lack thereof, from the
power-law mass profile in massive ellipticals through joint lensing-dynamics
analysis of a large statistical sample with 77 galaxy-galaxy lens systems. We
performed an improved and uniform lens modelling of these systems from archival
Hubble Space Telescope imaging using the automated lens modelling pipeline
dolphin. We combined the lens model posteriors with the stellar dynamics to
constrain the deviation from the power law after accounting for the
line-of-sight lensing effects, a first for analyses on galaxy-galaxy lenses. We
find that the Sloan Lens ACS Survey (SLACS) lens galaxies with a mean redshift
of 0.2 are consistent with the power-law profile within 1.1$sigma$
(2.8$sigma$) and the Strong Lensing Legacy Survey (SL2S) lens galaxies with a
mean redshift of 0.6 are consistent within 0.8$sigma$ (2.1$sigma$), for a
spatially constant (Osipkov-Merritt) stellar anisotropy profile. We adopted the
spatially constant anisotropy profile as our baseline choice based on previous
dynamical observables of local ellipticals. However, spatially resolved stellar
kinematics of lens galaxies are necessary to differentiate between the two
anisotropy models. Future studies will use our lens models to constrain the
mass distribution individually in the dark matter and baryonic components.
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