Volume 480, Number 2, March III 2008
|Page(s)||327 - 334|
|Section||Cosmology (including clusters of galaxies)|
|Published online||02 January 2008|
The multiple quasar Q2237+0305 under a microlensing caustic*
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstrasse 12-14, 69120 Heidelberg, Germany e-mail: email@example.com
2 Princeton University Observatory, Peyton Hall, Princeton, NJ 08544, USA
3 School of Physics, The University of Melbourne, Parkville, Victoria 3052, Australia
4 Apache Point Observatory, 2001 Apache Point Rd, Sunspot NM 88349, USA
Accepted: 22 November 2007
We use the high magnification event seen in the 1999 OGLE campaign light curve of image C of the quadruply imaged gravitational lens Q2237+0305 to study the structure of the quasar engine. We have obtained g'- and r'-band photometry at the Apache Point Observatory 3.5 m telescope where we find that the event has a smaller amplitude in the r'-band than in the g'- and OGLE V-bands. By comparing the light curves with microlensing simulations we obtain constraints on the sizes of the quasar regions contributing to the g'- and r'-band flux. Assuming that most of the surface mass density in the central kiloparsec of the lensing galaxy is due to stars and by modeling the source with a Gaussian profile, we obtain for the Gaussian width 1.201015 cm 7.96 10 cm, where M is the mean microlensing mass, and a ratio . With the limits on the velocity of the lensing galaxy from Gil-Merino et al. (2005) as our only prior, we obtain 0.601015 cm 1.571015 cm and a ratio (all values at 68 percent confidence). Additionally, from our microlensing simulations we find that, during the chromatic microlensing event observed, the continuum emitting region of the quasar crossed a caustic at ≥72 percent confidence.
Key words: gravitational lensing / galaxies: quasars: individual: Q2237+0305 / cosmology: observations / accretion, accretion disks
© ESO, 2008
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