Bibcode
Mediavilla, E.; Jiménez-Vicente, J.; Muñoz, J. A.; Battaner, E.
Bibliographical reference
The Astrophysical Journal, Volume 832, Issue 1, article id. 46, 11 pp. (2016).
Advertised on:
11
2016
Journal
Citations
10
Refereed citations
9
Description
We propose to use the flux variability of lensed quasar images induced
by gravitational microlensing to measure the transverse peculiar
velocity of lens galaxies over a wide range of redshift. Microlensing
variability is caused by the motions of the observer, the lens galaxy
(including the motion of the stars within the galaxy), and the source.
Hence, its frequency is directly related to the galaxy’s
transverse peculiar velocity. The idea is to count time-event rates
(e.g., peak or caustic crossing rates) in the observed microlensing
light curves of lensed quasars that can be compared with model
predictions for different values of the transverse peculiar velocity. To
compensate for the large timescale of microlensing variability, we
propose to count and model the number of events in an ensemble of
gravitational lenses. We develop the methodology to achieve this goal
and apply it to an ensemble of 17 lensed quasar systems. In spite of the
shortcomings of the available data, we have obtained tentative estimates
of the peculiar velocity dispersion of lens galaxies at z ∼ 0.5,
{σ }{pec}(0.53+/- 0.18)≃ (638+/- 213)\sqrt{<
m> /0.3 {M}ȯ } {km} {{{s}}}-1. Scaling at
zero redshift, we derive {σ }{pec}(0)≃ (491+/-
164)\sqrt{< m> /0.3 {M}ȯ } {km}
{{{s}}}-1, consistent with peculiar motions of nearby
galaxies and with recent N-body nonlinear reconstructions of the Local
Universe based on ΛCDM. We analyze the different sources of
uncertainty of the method and find that for the present ensemble of 17
lensed systems the error is dominated by Poisson noise, but that for
larger ensembles the impact of the uncertainty on the average stellar
mass may be significant.