Lens magnification by CL0024+1654 in the $\vec{U}$ and $\vec{R}$ band

Abstract

We estimate the total mass distribution of the galaxy cluster CL0024+1654 from the measured source depletion due to lens magnication in the R band. Within a radius of 0:54h 1 Mpc, a total projected mass of (8:1 3:2)10 14 h 1 M (EdS) is measured. The 1 error here includes shot noise, source clustering, uncertainty in background count normalisation and contamination from cluster and foreground galaxies. This corresponds to a mass-to-light ratio of M=LB = 470 180. We compute the luminosity function of CL0024+1654 in order to estimate contamination of the background source counts from cluster galaxies. Three dierent magnication- based reconstruction methods are employed: 1) an estimator method using a local calculation of lens shear; 2) a non-local, self-consistent method applicable to axi-symmetric mass distributions; 3) a non-local, self-consistent method for derivation of 2D mass maps. We have modied the standard single power-law slope number count theory to incorporate a break and applied this to our observations. Fitting analytical magnication proles of dierent cluster models to the observed number counts, we nd that CL0024+1654 is best described either by a NFW model with scale radius rs = 334 191h 1 kpc and normalisation s =0 :23 0:08 or a power-law prole with slope =0 :61 0:11, central surface mass density 0 =1 :52 0:20 and assuming a core radius of rcore =3 5h 1 kpc. The NFW model predicts that the cumulative projected mass contained within a radiusR scales as M(<R )=2 :9 10 14 (R=1 0 ) 1:3 0: 5l g(R=1 0 ) h 1 M. Finally, we have exploited the fact that flux magnication eectively enables us to probe deeper than the physical limiting magnitude of our observations in searching for a change of slope in the U band number counts. We rule out both a total flattening of the counts with a break up to UAB 26:6 and a change of slope, reported by some studies, from d logN=dm =0 :4! 0:15 up to UAB 26:4 with 95% condence.