Probing the relation between X-ray-derived and weak-lensing-derived masses forshear-selected galaxy clusters. I. A781

Neelima Sehgal, John P. Hughes, David Wittman, Vera Margoniner, J. Anthony Tyson, Perry Gee, Ian Dell'Antonio

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


We compare X-ray and weak-lensing masses for four galaxy clusters that comprise the top-ranked shear-selected cluster system in the Deep Lens Survey. The weak-lensing observations of this system, which is associated with A781, are from the Kitt Peak Mayall 4 m telescope, and the X-ray observations are from both Chandra and XMM-Newton. For a faithful comparison of masses, we adopt the same matter density profile for each method, which we choose to be an NFW profile. Since neither the X-ray nor the weak-lensing data are deep enough to well constrain both the NFW scale radius and central density, we estimate the scale radius using a fitting function for the concentration derived from cosmological hydrodynamic simulations and an X-ray estimate of the mass assuming isothermality. We keep this scale radius in common for both X-ray and weak-lensing profiles, and fit for the central density, which scales linearly with mass. We find that for three of these clusters, there is agreement between X-ray and weak-lensing NFW central densities, and thus masses. For the other cluster, the X-ray central density is higher than that from weak lensing by 2 a. X-ray images suggest that this cluster may be undergoing a merger with a smaller cluster. This work serves as an additional step toward understanding the possible biases in X-ray and weak-lensing cluster mass estimation methods. Such understanding is vital to efforts to constrain cosmology using X-ray or weak-lensing cluster surveys to trace the growth of structure over cosmic time.

Original languageEnglish (US)
Pages (from-to)163-175
Number of pages13
JournalAstrophysical Journal
Issue number1
StatePublished - Jan 20 2008

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Cosmology: observations
  • Galaxies: clusters: general
  • Galaxies: clusters: individual (A781)
  • Gravitational lensing
  • X-rays: galaxies: clusters


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