The ellipticity of galaxy cluster halos from satellite galaxies and weak lensing

Understand

We study the ellipticity of galaxy cluster halos as characterized by the distribution of cluster galaxies and as measured with weak lensing.

• We use monte-carlo simulations of elliptical cluster density profiles to estimate and correct for Poisson noise bias, edge bias and projection effects.
• We apply our methodology to 10,428 SDSS clusters identified by the redMaPPer algorithm with richness above 20.
• We find a mean ellipticity $= 0.271 \pm 0.002$ (stat) $\pm 0.031$ (sys) corresponding to an axis ratio $= 0.573 \pm 0.002$ (stat) $\pm 0.039$ (sys).