Clash: Precise New Constraints on the Mass Profile of the Galaxy Cluster A2261

Abstract

We precisely constrain the inner mass profile of Abell 2261 (z = 0.225) for the first time and determine this cluster is not "over-concentrated" as found previously, implying a formation time in agreement with ΛCDM expectations. These results are based on strong lensing analyses of new 16-band HST imaging obtained as part of the Cluster Lensing and Supernova survey with Hubble (CLASH). Combining this with revised weak lensing analyses of Subaru wide field imaging with 5band Subaru + KPNO photometry, we place tight new constraints on the halo virial mass M vir = 2.2 ± 0.2 × 10 15 M h −1 70 (within r vir ≈ 3 Mpc h −1 70 ) and concentration c vir = 6.2 ± 0.3 when assuming a spherical halo. This agrees broadly with average c(M, z) predictions from recent ΛCDM simulations which span 5 c 8. Our most significant systematic uncertainty is halo elongation along the line of sight. To estimate this, we also derive a mass profile based on archival Chandra X-ray observations and find it to be ∼ 35% lower than our lensing-derived profile at r 2500 ∼ 600 kpc. Agreement can be achieved by a halo elongated with a ∼ 2 : 1 axis ratio along our line of sight. For this elongated halo model, we find M vir = 1.7 ± 0.2 × 10 15 M h −1 70 and c vir = 4.6 ± 0.2, placing rough lower limits on these values. The need for halo elongation can be partially obviated by non-thermal pressure support and, perhaps entirely, by systematic errors in the X-ray mass measurements. We estimate the effect of background structures based on MMT/Hectospec spectroscopic redshifts and find these tend to lower M vir further by ∼ 7% and increase c vir by ∼ 5%.

Dark Matter Halo Profiles of Massive Clusters: Theory Versus Observations

“…Nevertheless, we note that there is a clear trend of lensing concentrations reducing over time and becoming more consistent with the theoretical predictions. Other data our results appear to be in agreement with can be found in Comerford & Natarajan (2007) (strong lensing) and Coe et al (2012) (strong and weak lensing). A cautionary note regarding weak lensing concentration measurements of clusters is provided in Figure 6 of Comerford & Natarajan (2007) regarding Abell 1689 and in the results given in Israel et al (2011) as part of the 400d weak lensing survey.…”

“…On the observational front, cluster (and group) halo profiles can be studied using both strong and weak gravitational lensing, individually, and in combination (see, e.g., Comerford & Natarajan 2007;Broadhurst et al 2008;Mandelbaum et al 2008;Okabe et al 2010;Oguri et al 2011;Zitrin et al 2011;Coe et al 2012), projected gas density and temperature profiles from X-ray observations (see, e.g., Vikhlinin et al 2006;Buote et al 2007;Schmidt & Allen 2007;Gastaldello et al 2007;Vikhlinin et al 2009;Sun et al 2009;Ettori et al 2011), and galaxy kinematics (Diaferio, Geller, & Rines 2005;Rines & Diaferio 2006;Wojtak & Lokas 2010 and references therein). Results from these observations have generally shown qualitative agreement with the c − M relation obtained from simulations, although there have been difficulties with matching the shape and normalization.…”

The projected gravitational potential of the galaxy cluster MACS J1206 derived from galaxy kinematics

“…The gravitational potential can then be projected along the line of sight. These methods complement our techniques for joint cluster reconstruction from weak and strong gravitational lensing Cacciato et al 2006;Merten et al 2009; see also Coe et al 2012;Merten et al 2011;Merten 2014 for examples).…”

A Multiply-Imaged z ∼ 6.3 Lyman Alpha Emitter candidate behind Abell 2261

“…The H-band (14,500-17,770Å) mask included a slit placed on multiple image 4a at (17:22:28.56, +32:08:07.92), using the ID given in Coe et al (2012). The image was identified initially using the method of Zitrin et al (2009), which is the one used here for lens modeling as well.…”