Probing the Relation Between X-Ray-Derived and Weak-Lensing-Derived Masses for Shear-Selected Galaxy Clusters. I. A781
Abstract
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 σ. 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2008
- DOI:
- 10.1086/523840
- arXiv:
- arXiv:0706.2351
- Bibcode:
- 2008ApJ...673..163S
- Keywords:
-
- cosmology: observations;
- galaxies: clusters: general;
- galaxies: clusters: individual: A781;
- gravitational lensing;
- X-rays: galaxies: clusters;
- Astrophysics
- E-Print:
- 14 pages, 7 figures, matches version in ApJ