The 400d Galaxy Cluster Survey Weak Lensing Programme: I: MMT/Megacam Analysis of CL0030+2618 at z=0.50

TL;DR

This paper demonstrates the effectiveness of deep imaging with MEGACAM at MMT for measuring weak lensing signals of high-redshift galaxy clusters, providing reliable mass estimates and validating the method for future large surveys.

Contribution

It presents the first weak lensing analysis of the high-redshift cluster CL0030+2618 using MMT/Megacam, showing the instrument's suitability and achieving significant mass measurement.

Findings

Detected weak lensing signal at 5.8 sigma significance

Measured a virial mass of 7.5 x 10^{14} solar masses

Weak lensing and X-ray mass estimates are in agreement

Abstract

The mass function of galaxy clusters at high redshifts is a particularly useful probe to learn about the history of structure formation and constrain cosmological parameters. We aim at deriving reliable masses for a high-redshift, high-luminosity sample of clusters of galaxies selected from the 400d survey of X-ray selected clusters. Here, we will focus on a particular object, CL0030+2618 at z=0.50 Using deep imaging in three passbands with the MEGACAM instrument at MMT, we show that MEGACAM is well-suited for measuring gravitational shear. We detect the weak lensing signal of CL0030+2618 at 5.8 sigma significance, using the aperture mass technique. Furthermore, we find significant tangential alignment of galaxies out to ~10 arcmin or >2r_200 distance from the cluster centre. The weak lensing centre of CL0030+2618 agrees with several X-ray measurements and the position of the brightest cluster galaxy. Finally, we infer a weak lensing virial mass of M_200=7.5 10^{14} M_sun for CL0030+2618. Despite complications by a tentative foreground galaxy group in the line of sight, the X-ray and weak lensing estimates for CL0030+2618 are in remarkable agreement. This study paves the way for the largest weak lensing survey of high-redshift galaxy clusters to date.