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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

2009; IOP Publishing; Volume: 691; Issue: 1 Linguagem: Inglês

10.1088/0004-637x/691/1/531

1538-4357

G. Covone, M. Paolillo, N. R. Napolitano, M. Capaccioli, G. Longo, Jean‐Paul Kneib, Eric Jullo, Johan Richard, O. S. Khovanskaya, M. V. Sazhin, Norman A. Grogin, E. Schreier,

Astronomy and Astrophysical Research

We analyze a new gravitational lens, OAC-GL J1223-1239, serendipitously found in a deep I-band image of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS). The lens is a L_*, edge-on S0 galaxy at z=0.4656. The gravitational arc has a radius of 0.42 arcsec. We have determined the total mass and the dark matter (DM) fraction within the Einstein radius as a function of the lensed source redshift, which is presently unknown. For z ~ 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. 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 the Einstein radius (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.