Compact group analysis using weak gravitational lensing

FÖEX, GAEL; CHALELA, MARTÍN; GONZALEZ, ELIZABETH JOHANA; LAMBAS, DIEGO GARCIA; FÖEX, GAEL; CHALELA, MARTÍN; GONZALEZ, ELIZABETH JOHANA; LAMBAS, DIEGO GARCIA

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2017 vol. 467 p. 1819 - 1829

0035-8711

We present a weak lensing analysis of a sample of Sloan Digital Sky Survey compact groups (CGs). Using the measured radial density contrast profile, we derive the average masses under the assumption of spherical symmetry, obtaining a velocity dispersion for the singular isothermal spherical model, σV = 270 ± 40 km s-1, and for the NFW model, R200 = 0.53 ± 0.10 h 70-1 Mpc. We test three different definitions of CG centres to identify which best traces the true dark matter halo centre, concluding that a luminosity-weighted centre is the most suitable choice. We also study the lensing signal dependence on CG physical radius, group surface brightness and morphological mixing. We find that groups with more concentrated galaxy members show steeper mass profiles and larger velocity dispersions. We argue that both, a possible lower fraction of interloper and a true steeper profile, could be playing a role in this effect. Straightforward velocity dispersion estimates from member spectroscopy yield σV ≈ 230 km s-1 in agreement with our lensing results.