The Surprisingly Steep Mass Profile of A1689, from a Lensing Analysis of Subaru Images

Abstract

Subaru observations of A1689 (z = 0.183) are used to derive an accurate, model-independent mass profile for the entire cluster, r < ∼ 2Mpc/h, by combining magnification bias and distortion measurements. The projected mass profile steepens quickly with increasing radius, falling away to zero at r ∼ 1.0Mpc/h, well short of the anticipated virial radius. Our profile accurately matches onto the inner profile, r < ∼ 200kpc/h, derived from deep HST/ACS images. The combined ACS and Subaru information is well fitted by an NFW profile with virial mass, (1.93 ± 0.20) × 10 15 M ⊙ , and surprisingly high concentration, c vir = 13.7 +1.4 −1.1 , significantly larger than theoretically expected (c vir ≃ 4), corresponding to a relatively steep overall profile. A slightly better fit is achieved with a steep power-law model, d logΣ(θ)/d logθ ≃ −3, with a core θ c ≃ 1. ′ 7 (r c ≃ 210kpc/h), whereas an isothermal profile is strongly rejected. These results are based on a reliable sample of background galaxies selected to be redder than the cluster E/S0 sequence. By including the faint blue galaxy population a much smaller distortion signal is found, demonstrating that blue cluster members significantly dilute the true signal for r < ∼ 400kpc/h. This contamination is likely to affect most weak lensing results to date.

Weak lensing density profiles and mass reconstructions of the galaxy clusters Abell 1351 and Abell 1995

“…Kneib et al (2003) found c = 22 +9 −5 for the central mass concentration of the cluster Cl 0024 + 1654. Gavazzi (2005) concluded on c = 11.73 ± 0.55 for MS2137 − 23, while Broadhurst et al (2005) found c = 13.7 +1.4 −1.1 for Abell 1689. Limousin et al (2007) presented a thorough discussion of the different concentration parameters derived for Abell 1689 in the literature, concluding that a distribution of best fit c parameters is needed for observed lensing clusters in order to provide a sample large enough to make an adequate comparison with simulations.…”

LoCuSS: weak-lensing mass calibration of galaxy clusters

“…This is often referred to as a dilution effect, because the contaminants dilute the signal (Broadhurst et al 2005;Umetsu et al 2010;Okabe et al 2010aOkabe et al , 2013. The dominant source of contaminant galaxies is faint cluster members, the number density of which increases towards the cluster core.…”

“…Broadhurst et al 2005;Limousin et al 2007). It is therefore of prime importance to make a secure selection of background galaxies.…”

A predicted relation between the temperature and density profile of cluster hot gas

“…(7) has a soft core which is different from the NFW profile obtained by N-body simulation. Nevertheless, recent gravitational lensing data support the existence of soft cores in clusters, in contradiction to the NFW profile (Tyson et al 1998;Sand et al 2002;Broadhurst 2005). …”