Introduction

The interpretation of gravitational lensing effects by galaxy clusters is complicated by the fact that lenses have unknown three-dimensional shapes, fairly well described by triaxial mass districutions. Lensing only probes the projected mass distribution of the lenses (or, better, their projected gravitational potential). In many cases, however, we aim at probing three-dimensional quantities, such as masses, density profiles, etc. In absence of better knwoledge of the lens shapes, it is a common practice to de-project the lensing signal by making the strong assumption of spherical symmetry. As shown in e.g. Meneghetti et al. (2010), this introduces significant uncertainties in the measurements of some structural properties of Galaxy Clusters.

Sometimes, the selection function used to build a sample of lenses introduces strong orientation biases. For example, using numerical simulations Hennawi et al. 2007 and by Meneghetti et al. 2010 showed that clusters selected for being strong gravitational lenses tend to have their major axes pointing preferentially towards the observer. Under these circumstances, lenses may appear overdense on the plane of the sky and de-projecting their mass distribution assuming sphericity may result in overestimating both the mass and the cooncentration of their dark matter halos.

CLASH

The Cluster Lensing And Supernova survey with Hubble (CLASH, PI Marc Postman) is a treasury program of the Hubble Space Telescope targeting a sample of 25 galaxy clusters observed in 16 bands using the Advanced Camera for Survey (ACS) and the Wide Field Camera 3 (WFC3). Twenty of the CLASH clusters were selected because of their regular X-ray morphology and high temperature. Among the criteria used to quantify the X-ray morphology are the ellipticity of the surface brightness distribution, the concentration of the X-ray emission and the degree of asymmetry of the iso-surface-brightness contours.

MUSIC-2 and CLASH

Aiming at comparing the masses and concentrations of the CLASH clusters with the theoretical expectations in the framework of LCDM , we mimicked the selection function of the CLASH relaxed sub-sample. For each CLASH cluster, we identified a number of cluster-sized halos in the MUSIC-2 simulations having X-ray morphologies consistent with the observed ones. The X-ray morphologies of both simulated and real clusters were consistently evaluated via 5 different morphological estimators. The MUSIC project is a collaboration between UAM, Sapienza and the Leibniz Institute of Astrohysics at Potsdam. The MUSIC-2 simulations consist of halos extracted from the Multidark database.

Products

The BLF portal gives access to convergence, shear and magnification maps for all CLASH-like clusters in the MUSIC-2 simulation set. In addition it provides their density and surface-density profiles.

To download the data products, use the BLF portal

References

  • The CLASH web site is at this URL
  • More information about the MUSIC project can be found here
  • More information the MUSIC of CLASH project can be found in the paper by Meneghetti et al. (2014)

People

Funding

This program is supported via the PRIN-INAF 2014 "Glittering Kaleidoscopes in the sky, the multifaceted nature and role of galaxy clusters" (PI. M. Nonino), coordinated at INAF-OABO by M. Meneghetti.