Limits on the transverse velocity of the lensing galaxy in Q2237+0305 from the lack of strong microlensing variability

Free access article

Issue		A&A Volume 432, Number 1, March II 2005


Page(s)		83 - 89
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20047123

A&A 432, 83-89 (2005)
DOI: 10.1051/0004-6361:20047123

Limits on the transverse velocity of the lensing galaxy in Q2237+0305 from the lack of strong microlensing variability

R. Gil-Merino, J. Wambsganss, L. J. Goicoechea and G. F. Lewis

Universidad de Cantabria, Departamento de Física Moderna, Avda. de Los Castros s/n, 39005 Santander, Spain
    e-mail: [gilmerinor;goicol]@unican.es Astronomisches Rechen-Institut (ARI) and Universität Heidelberg, Mönschhofstr. 12-14, 69120 Heidelberg, Germany
    e-mail: jkw@ari.uni-heidelberg.de University of Sydney, Institute of Astronomy, School of Physics A28, NSW 2006, Australia
    e-mail: gfl@physics.usyd.edu.au

(Received 22 January 2004 / Accepted 2 November 2004)

Abstract
We present a method for the determination of upper limits on the transverse velocity of the lensing galaxy in the quadruple quasar system Q2237+0305, based on the lack of strong microlensing signatures in the quasar lightcurves. The limits we derive here are based on four months of high quality monitoring data, by comparing the low amplitudes of the lightcurves of the four components with extensive numerical simulations. We make use of the absence of strong variability of the components (especially components B and D) to infer that a "flat" time interval of such a length is only compatible with an effective transverse velocity of the lensing galaxy of ${v_{\rm bulk}}~\leq~630$ km s ^-1 for typical microlenses masses of $M_{\rm\mu lens}=0.1~M_{\odot}$ (or ${v_{\rm bulk}}~\leq~2160$ km s ^-1 for $M_{\rm\mu lens}=1.0~M_{\odot}$ ) at the 90% confidence level. This method may be applicable in the future to other systems.

Key words: gravitational lensing -- galaxies: quasars: individual: Q2237+0305 -- methods: numerical

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