Gauging the Dark Matter Fraction in an L S0 Galaxy at z = 0.47 Through Gravitational Lensing from Deep Hubble Space Telescope/Advanced Camera for Surveys Imaging

• Published in: The Astrophysical journal 2009-01, Vol.691 (1), p.531-536
• Main Authors: Covone, G, Paolillo, M, Napolitano, N. R, Capaccioli, M, Longo, G, Kneib, J.-P, Jullo, E, Richard, J, Khovanskaya, O, Sazhin, M, Grogin, N. A, Schreier, E
• Format: Article
• Language: English
• Subjects: Astrophysics; Cosmology and Extra-Galactic Astrophysics; Physics; Sciences of the Universe
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/691/1/531

We analyze a new gravitational lens OAC-GL J1223-1239, serendipitously found in a deep I 814-band image of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS). The lens is an L*, edge-on S0 galaxy at z l = 0.4656. The gravitational arc has a radius of 042 1.74 h -1 kpc. We have determined the total mass and the dark matter (DM) fraction within the Einstein radius R E as a function of the lensed source redshift, which is presently unknown. For z s ~ 1.3, which is in the middle of the redshift range plausible for the source according to some external constraints, we find the central velocity dispersion to be ~180 km s -1. With this value, close to that obtained by means of the Faber-Jackson relation at the lens redshift, we compute a 30% DM fraction within R E (given the uncertainty in the source redshift, the allowed range for the DM fraction is 25%-35% in our lensing model). When compared with the galaxies in the local universe, the lensing galaxy OAC-GL J1223-1239 seems to fall in the transition regime between massive, DM-dominated galaxies and lower-mass, DM-deficient systems.