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A Gravitational Lens Candidate Behind The Fornax Dwarf Spheroidal Galaxy

Published online by Cambridge University Press:  25 May 2016

C.G. Tinney*
Affiliation:
Anglo-Australian Observatory, PO Box 296, Epping. NSW. 2121 Australia

Extract

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CCD astrometry makes possible milli-arcsecond precision relative astrometry at faint magnitudes (Tinney 1994a). The measurement of proper motions for the nearest galaxies is therefore a project requiring only years – not decades. A prerequisite for such measurements, however, is a set of unresolved, extragalactic reference objects – ie. QSOs. While searching for such objects behind the Fornax dSph galaxy, Tinney (1995b) discovered the QJ0240-343AB system as a pair of bright, UV-excess objects (U-B = −1.0, B = 19.0 & 19.8) with a separation of 6.1″. Spectra obtained with the 3.9 m Anglo-Australian telescope and the RGO+FORS spectrographs (Fig. 1) have shown both components of the pair to be at a redshift of z = 1.4, with a rest velocity difference consistent with zero at a 1-σ limit of 180 km/s. The spectra also show a definite metal-line absorption system at z = 0.543 and a possible system at z = 0.337. No bright lens is seen, but the strong similarities in the spectra suggest a gravitational lens nature.

Type
Chapter 9: Observational Developments
Copyright
Copyright © Kluwer 1996 

References

Demers, S., Irwin, M. & Kunkel, W. 1995, AJ, 108, 1648 CrossRefGoogle Scholar
Tinney, C.G. 1995a, in Science with the VLT, eds. Walsh, J.R. & Danziger, I.J., (Springer-Verlag: Heidelberg)Google Scholar
Tinney, C.G. 1995b, MNRAS, in press Google Scholar