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Paper: The BL Lac Object PKS 0537-441: A Lens or Being Lensed?
Volume: 299, High Energy Blazar Astronomy
Page: 293
Authors: Heidt, J.; Jager, K.; Nilsson, K.; Hopp, U.; Fried, J.W.; Sutorius, E.
Abstract: We present and discuss deep high-resolution images taken with the ESO-NTT as well as spectra taken with the ESO-VLT in the field of PKS 0537-441. We could neither detect the host galaxy nor a galaxy along the line-of-sight to the BL Lac as claimed from previous observations. We found 4 nearby companion galaxies which could be a splitted and magnified image of a distant background galaxy. Our VLT-spectra, however, rule out this possibility. All 4 companions have similar redshifts as the BL Lac and may (at least in part) trigger the enormous activity in this source. PKS 0537-441 might be located in a galaxy cluster as rich as Abell 1. Alternatively, the BL Lac could also be located in the outskirts of a galaxy cluster or even be projected on a large-scale structure as indicated by spectra of 30 galaxies in the field. Either lensing hypothesis (lens or being lensed) can be ruled out with high confidence by our observations.
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