The BL Lac Object PKS 0537-441： A Lens or Being Lensed?

Jochen Heidt; Klaus Jger; Kari Nilsson; Ulrich Hopp; Josef W. Fried; Eckhard Sutorius

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Publications of the Yunnan Observatory > 2003 > 0(S1): 117-120.

Jochen Heidt, Klaus Jger, Kari Nilsson, Ulrich Hopp, Josef W. Fried, Eckhard Sutorius. The BL Lac Object PKS 0537-441： A Lens or Being Lensed?[J]. Publications of the Yunnan Observatory, 2003, (S1): 117-120.

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The BL Lac Object PKS 0537-441： A Lens or Being Lensed?

1.
Landessternwarte, Königstuhl, D-69117 Heidelberg, Germany
2.
USG, Geismarlandstr.11, D-37083Göttingen, Germany
3.
Tuorla Observatory, FIN-21500 Piikkiö
, Finland
4.
USM, Scheinerstr.1, D-81679München, Germany
5.
MPIA, Königstuhl 17, D-69117 Heidelberg, Germany
6.
ROE, Blackford Hill, Edinburgh EH9 3HJ, United Kingdom.

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Published Date: October 30, 2003

Graphical Abstract

Abstract

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 the BL Lac object 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)is considerably weakened by our observations.