Mon. Not. R. Astron. Soc., 373, 1369-1378 (2006/December-3)
Constraints on the velocity profiles of galaxies from strong lensing statistics and semi-analytical modelling of galaxy formation.
CHAE K.-H., MAO S. and KANG X.
Abstract (from CDS):
Semi-analytical models of galaxy formation can be used to predict the evolution of the number density of early-type galaxies as a function of the circular velocity at the virial radius, vc,vir. Gravitational lensing probability and separation distribution on the other hand are sensitive to the velocity dispersion (or circular velocity) at about the effective radius. We adopt the singular isothermal ellipsoid (SIE) lens model to estimate the velocity dispersion at the effective radius. The velocity dispersion from strong lensing based on the SIE, σSIEis then closely related to the observational central stellar velocity dispersion, σcent; we have empirically σSIE~ σcent. We use radio lenses from the Cosmic Lens All-Sky Survey and the PMN-NVSS Extragalactic Lens Survey to study how the velocity dispersions, σSIE, are related to vc,vir; if the galaxy were a singular isothermal sphere up to the virial radius,. When we include both the lensing probability and separation distribution as our lensing constraints, we find for 200km/s ≲ σSIE≲ 260km/s; at σSIE= 200km/s, the ratio is about 1.65+0.57–0.37[68 per cent confidence limit (CL)] but decreases to 0.65+0.15–0.12(68 per cent CL) for σSIE= 260km/s. These results are consistent with those of Seljak obtained from galaxy-galaxy weak lensing for galaxies of around L*. However, our results clearly suggest that the ratio must vary significantly as σSIEis varied and are marginally discrepant with the Seljak results at σSIE= 260km/s. The scaling σSIE ∝ v0.22±0.05c,viris broadly consistent with those from galaxy occupation statistics studies and the most recent galaxy-galaxy weak lensing study. We discuss briefly the implications of our results for galaxy formations and structures. These constraints can be significantly strengthened when larger lens samples become available and the accuracy of semi-analytical model predictions improves.
2006 The Authors. Journal compilation © 2006 RAS
gravitational lensing - galaxies: formation - galaxies: haloes - galaxies: kinematics and dynamics - galaxies: structure
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