Light Deflection and Absorption of high-redshift Quasars by intervening Galaxy Systems

Abstract

The light of a distant quasar can be affected by deflection and absorption by intervening galaxy systems. One example of strong absorption is the damped Lyman-alpha (DLA) system towards the quasar PKS0458-020, in which HI Lyman-alpha is also detected in emission in the center of the damped Lyman-alpha absorption trough. We estimate the star formation rate of the DLA galaxy to be 1.6 M_sun/year. The associated metal lines are found to be blueshifted compared to the Lyman-alpha emission up to a maximum of 100 and 200km/s. This can be interpreted either as the consequence of rotation in a large disk (~7kpc) or as the imprint of a galactic wind. In a similar study, the analysis of Lyman-alpha and metal absorption lines in the spectra of the quasar pair Q 0037-3544 and Q 0037-3545 reveal the spatial extent of absorbing structures. We obtained deep images of the field around the two quasars that allow us to identify galaxies at redshifts corresponding to the observed absorptions, indicating that the absorbing structures extend over a distance of 760kpc. The effect of quasar light deflection is analyzed by studying the variability of the wide separation quintuple gravitational lensed quasar SDSS J1004+4112. Four years of optical monitoring were obtained for the four brightest images. These light curves allow the measurement of the differences in the light arrival times, the time delay, between the images. The measured time delay between the image pair B and A is 40.6+-1.8 days and between images C and A 821.6+-2.1 days (2.3 years). The time delay between the images C and A is the longest measured time delay in a gravitationally lensed quasar so far. A lower limit on the remaining delay between image A and D of 1250 days is derived. We detect microlensing and characterize the intrinsic variability of the quasar.