CLASH: Precise new constraints on the mass profile of the galaxy cluster A2261

Dan Coe, Keiichi Umetsu, Adi Zitrin, Megan Donahue, Elinor Medezinski, Marc Postman, Mauricio Carrasco, Timo Anguita, Margaret J. Geller, Kenneth J. Rines, Antonaldo Diaferio, Michael J. Kurtz, Larry Bradley, Anton Koekemoer, Wei Zheng, Mario Nonino, Alberto Molino, Andisheh Mahdavi, Doron Lemze, Leopoldo InfanteSara Ogaz, Peter Melchior, Ole Host, Holland Ford, Claudio Grillo, Piero Rosati, Yolanda Jiménez-Teja, John Moustakas, Tom Broadhurst, Begoña Ascaso, Ofer Lahav, Matthias Bartelmann, Narciso Benítez, Rychard Bouwens, Or Graur, Genevieve Graves, Saurabh Jha, Stephanie Jouvel, Daniel Kelson, Leonidas Moustakas, Dan Maoz, Massimo Meneghetti, Julian Merten, Adam Riess, Steve Rodney, Stella Seitz

Research output: Contribution to journalArticlepeer-review

113 Scopus citations


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 languageEnglish (US)
Article number22
JournalAstrophysical Journal
Issue number1
StatePublished - Sep 20 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • dark energy
  • dark matter
  • galaxies: clusters: individual (Abell 2261)
  • galaxies: evolution
  • gravitational lensing: strong
  • gravitational lensing: weak


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