Noisy weak-lensing convergence peak statistics near clusters of galaxies and beyond

Abstract

Taking into account noise from intrinsic ellipticities of source galaxies, in this paper, we study the peak statistics in weak-lensing convergence maps around clusters of galaxies and beyond. We emphasize how the noise peak statistics is affected by the density distribution of nearby clusters, and also how cluster-peak signals are changed by the existence of noise. These are the important aspects to be understood thoroughly in weak-lensing analyses for individual clusters as well as in cosmological applications of weak-lensing cluster statistics. We adopt Gaussian smoothing with the smoothing scale $\theta_G=0.5\hbox{ arcmin}$ in our analyses. It is found that the noise peak distribution near a cluster of galaxies depends sensitively on the density profile of the cluster. For a cored isothermal cluster with the core radius $R_c$, the inner region with $R\le R_c$ appears noisy containing on average $\sim 2.4$ peaks with $\nu\ge 5$ for $R_c= 1.7\hbox{ arcmin}$ and the true peak height of the cluster $\nu=5.6$, where $\nu$ denotes the convergence signal to noise ratio. For a NFW cluster of the same mass and the same central $\nu$, the average number of peaks with $\nu\ge 5$ within $R\le R_c$ is $\sim 1.6$. Thus a high peak corresponding to the main cluster can be identified more cleanly in the NFW case. In the outer region with $R_c<R\le 5R_c$, the number of high noise peaks is considerably enhanced in comparison with that of the pure noise case without the nearby cluster. (abridged)