The study of gravitational lenses has become a powerful tool to address several distinct cosmological and astrophysical questions. These include the distribution of dark matter in galaxies (Keeton et al. 1998), studying dust extinction at redshift (Nadeau et al. 1991; Jean & Surdej 1998), and determining the Hubble parameter from measurements of light travel time delay between different lines of sight (Refsdal 1964). The appeal of this method lies in its complete independence of the traditional cosmic distance ladder, yielding distances for high-redshift objects in a single leap.
The uncertainties of estimation are mainly limited by ambiguities in modelling the deflector mass distribution, since all relevant measurement errors can be reduced to insignificance. While `simple' lenses such as double QSOs do not strongly constrain the deflector model, multiple systems such as quadruply imaged QSOs provide many additional constraints, allowing e.g. to independently test the assumed mass distribution models (cf. Saha & Williams 1997). A problem with quadruple systems, however, can be excessive symmetry leading to time delays which are short compared to intrinsic radio and optical variability timescales, as in the famous `Einstein Cross' 2237+030 or in the `Clover Leaf ' H 1413+117.
In this paper we present the discovery of the new multiple QSO HE 0230-2130. The object was originally identified as a high-probability QSO candidate in the course of the Hamburg/ESO survey (Wisotzki et al. 1996) and subsequently observed as part of a large imaging search for lensed QSOs. The coordinates of this object are R.A. = , Dec = (J2000.0), as measured in the Digitized Sky Survey .
© European Southern Observatory (ESO) 1999
Online publication: July 26, 1999