Bibcode
Urry, C. M.; Scarpa, R.; O'Dowd, M.; Broadhurst, T.; Falomo, R.; Treves, A.; Webster, R.; Sillanpaa, A.; Takalo, L.; Heidt, H.
Bibliographical reference
American Astronomical Society, 194th AAS Meeting, #73.08; Bulletin of the American Astronomical Society, Vol. 31, p.951
Advertised on:
5
1999
Citations
0
Refereed citations
0
Description
The HST snapshot survey of 108 BL Lac objects has revealed several
instances of unusual morphologies, three jets and a possible Einstein
ring. Of the three detected optical jets, two were already known (PKS
0521-365 and 3C371) and one is a new discovery (PKS 2201+044). At HST
resolution the jets are well resolved and individual knots clearly seen,
closely corresponding to the radio knots. The derived radio-to-optical
spectral index is remarkably constant along each jet, implying similar
conditions in each knot, and indeed similarity among the three sources.
Considerations of the energy budgets of these and other known optical
jets constrain the presence of bulk relativistic motion on kiloparsec
scales, the intrinsic magnetic field strengths, and the need for
reacceleration along the jet. The most unusual morphology in the survey
is a ring-like structure around an unresolved BL Lac object at z>0.7.
The most plausible of several possible explanations is that the BL Lac
object has lensed one or two background galaxies into arcs approximating
an Einstein ring. We present composite images from a joint deconvolution
of the HST image and ground-based images from the NOT and CFHT
telescopes, as well as a tentative model of the system.