Astronomy and Astrophysics – Astrophysics
Scientific paper
1995-12-23
Astrophys.J. 473 (1996) 570
Astronomy and Astrophysics
Astrophysics
Submitted to ApJ. 49 pages; aaspp latex + 5 postscript figures, uuencoded gzipped tar archive. Hardcopies available by request
Scientific paper
10.1086/178171
We present a simple mass model for the lensing galaxy in the gravitationally lensed quasar 0957+561. The model is a generalization of the singular isothermal sphere and includes a core radius, $r_c$, and a power-law index, $\eta$, defined such that mass increases as $r^\eta$ at large radius. We approximate the galaxy cluster surrounding the lensing galaxy with a quadratic potential described by its convergence $\kappa$ and shear $\gamma$. We fit the model to a recent high resolution VLBI map of the two images of 0957+561. We obtain a tight constraint on the radial index, $1.07 < \eta <1.18$, which means that the lens galaxy is nearly isothermal with increasing mass-to-light ratio out to $15 h^{-1}$ kpc. We also obtain an upper limit on the core radius, $r_c < 330 h^{-1}$ pc. We use the model to calculate the Hubble constant $H_0$ as a function of the time delay $\Delta\tau_{BA}$ between the two images: $H_0 = \left({ 82.5^{+5.9} _{-3.0} }\right) (1 - \kappa) \left({ \Delta\tau_{BA}/1.1 \,{\rm yr} }\right)^{-1}$ km/s/Mpc. Once $\Delta \tau_{BA}$ is measured, this will provide an upper bound on $H_0$ since $\kappa$ cannot be negative. In addition, the model degeneracy due to $\kappa$ can be eliminated if the one-dimensional velocity dispersion $\sigma$ of the lensing galaxy is measured. We then have $H_0 = \left({ 82.5^{+8.7} _{-5.6} }\right) (\sigma / 322\,{\rm km/s})^2 \left({ \Delta \tau_{BA} /1.1 \,{\rm yr} }\right)^{-1}$ km/s/Mpc. We investigate the effects of ellipticity in the lensing galaxy and clumpiness in the lensing cluster and find that these cause little change in our results.
Grogin Norman Andrew
Narayan Ramesh
No associations
LandOfFree
A New Model of the Gravitational Lens 0957+561 and a Limit on the Hubble Constant does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A New Model of the Gravitational Lens 0957+561 and a Limit on the Hubble Constant, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A New Model of the Gravitational Lens 0957+561 and a Limit on the Hubble Constant will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-273255