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arXiv · 0809.4125

Gauging the dark matter fraction in a $L_*$ S0 galaxy at z=0.47 through gravitational lensing from deep HST/ACS imaging

G. Covone·M. Paolillo·N. R. Napolitano·M. Capaccioli·G. Longo·J. -P. Kneib·E. Jullo·J. Richard·O. Khovanskaya·M. Sazhin·N. A. Grogin·E. Schreier
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Abstract

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.

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G. Covone, M. Paolillo, N. R. Napolitano, M. Capaccioli, G. Longo, J. -P. Kneib, E. Jullo, J. Richard, O. Khovanskaya, M. Sazhin, N. A. Grogin, E. Schreier. 2008-09-24. Gauging the dark matter fraction in a $L_*$ S0 galaxy at z=0.47 through gravitational lensing from deep HST/ACS imaging. https://doi.org/10.1088/0004-637x%2F691%2F1%2F531

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