Extinction properties of lensing galaxies
Nov, 2007Citations per year
Abstract: (arXiv)
Context. Observations of quasars shining through foreground galaxies offer a way to probe the dust extinction curves of distant galaxies. Interesting objects for this study can be found in strong gravitational lensing systems, where the foreground galaxies cause multiple images. Aims. The reddening law of lensing galaxies have been investigated by studying colours of gravitationally lensed quasars and a handful of other quasars where a foreground galaxy is detected. Methods. The analysis was made by comparing the observed colours of quasar images in the literature with spectral templates reddened with different extinction laws and dust properties. Our sample consists of 21 quasar-galaxy systems with a total of 48 images. The galaxies, which are both early and late type, have redshifts in the interval z=0.04-1.51. Results. The difference in rest frame B-V for our set of quasar images compared to quasars without resolved foreground galaxies indicates that the quasar colours are affected by dust extinction in the intervening galaxy. Good fits to standard extinction laws were found for 22 of the images, corresponding to 13 different galaxies. Our fits yield a wide range of best values for the total-to-selective extinction ratio, Rv. The distribution was found to be broad with a weighted mode of Rv=2.4 and a FWHM of 2.7 (sigma = 1.1). Thus the bulk of the galaxies considered in this study for which good reddening fits could be made has dust properties compatible with the Milky Way value (Rv=3.1).References(41)
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