2016A&A...594A.121P

Aims. We present a new strong lensing mass reconstruction of the Bullet cluster (1E 0657-56) at z=0.296, based on WFC3 and ACS HST imaging and VLT/FORS2 spectroscopy. The strong lensing constraints underwent substantial revision compared to previously published analysis, there are now 14 (six new and eight previously known) multiply-imaged systems, of which three have spectroscopically confirmed redshifts (including one newly measured from this work).
Methods. The reconstructed mass distribution explicitly included the combination of three mass components: (i) the intra-cluster gas mass derived from X-ray observation; (ii) the cluster galaxies modeled by their fundamental plane scaling relations and (iii) dark matter.
Results. The model that includes the intra-cluster gas is the one with the best Bayesian evidence. This model has a total rms value of 0.158'' between the predicted and measured image positions for the 14 multiple images considered. The proximity of the total rms to resolution of HST/WFC3 and ACS (0.07-0.15''FWHM) demonstrates the excellent precision of our mass model. The derived mass model confirms the spatial offset between the X-ray gas and dark matter peaks. The fraction of the galaxy halos mass to total mass is found to be f_s=11±5% for a total mass of 2.5±0.1x10¹⁴M_☉ within a 250kpc radial aperture.