Abstract
We precisely constrain the inner mass profile of A2261 (z = 0.225) for the first time and determine that this cluster is not "overconcentrated" as found previously, implying a formation time in agreement with ΛCDM expectations. These results are based on multiple strong-lensing analyses of new 16-band Hubble Space Telescope imaging obtained as part of the Cluster Lensing and Supernova survey with Hubble. Combining this with revised weak-lensing analyses of Subaru wide-field imaging with five-band Subaru + KPNO photometry, we place tight new constraints on the halo virial mass Mvir = (2.2 ± 0.2) × 1015 M⊙ h -1 70 (within rvir ≈ 3 Mpc h-170) 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 (LOS). 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 r2500 ∼ 600kpc. Agreement can be achieved by a halo elongated with a 2:1 axis ratio along our LOS. For this elongated halo model, we find Mvir = (1.7 ± 0.2) × 1015 M ⊙ h-170 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 that these tend to lower M vir further by ∼7% and increase cvir by ∼5%.
Original language | English (US) |
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Article number | 22 |
Journal | Astrophysical Journal |
Volume | 757 |
Issue number | 1 |
DOIs | |
State | Published - Sep 20 2012 |
Externally published | Yes |
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
Keywords
- dark energy
- dark matter
- galaxies: clusters: individual (Abell 2261)
- galaxies: evolution
- gravitational lensing: strong
- gravitational lensing: weak