Two new large-separation gravitational lenses from SDSS

Belokurov, V.; Evans, N. W.; Hewett, P. C.;Moiseev, A.; McMahon, R. G.; Sanchez, S. F.;King, L. J.. Two new large-separation gravitational lenses from SDSS. Monthly Notices of the Royal Astronomical Society. 2009, Vol. Volume 392, Issue 1, pp. 104-112., p. -2009.

We present discovery images, together with follow-up imaging and
spectroscopy, of two large-separation gravitational lenses found by our
survey for wide arcs [the CAmbridge Sloan Survey Of Wide ARcs in the skY
(CASSOWARY)]. The survey exploits the multicolour photometry of the
Sloan Digital Sky Survey to find multiple blue components around red
galaxies. CASSOWARY 2 (or `the Cheshire Cat') is composed of two massive
early-type galaxies at z = 0.426 and 0.432, respectively, lensing two
background sources, the first a star-forming galaxy at z = 0.97 and the
second a high -redshift galaxy (z > 1.4). There are at least three
images of the former source and probably four or more of the latter,
arranged in two giant arcs. The mass enclosed within the larger arc of
radius ~11 arcsec is ~33 × 10<SUP>12</SUP>M<SUB>solar</SUB>.
CASSOWARY 3 comprises an arc of three bright images of a z = 0.725
source, lensed by a foreground elliptical at z = 0.274. The radius of
the arc is ~4 arcsec and the enclosed mass is ~2.5 ×
10<SUP>12</SUP>M<SUB>solar</SUB>. Together with earlier discoveries like
the Cosmic Horseshoe and the 8 o'clock Arc, these new systems, with
separations intermediate between the arcsecond-separation lenses of
typical strong galaxy lensing and arcminute-separation cluster lenses,
probe the very high end of the galaxy mass function.