Multiwavelength Analysis of A1240, the Double Radio Relic Merging Galaxy Cluster Embedded in a ~80 Mpc-long Cosmic Filament

We present a multiwavelength study of the double radio relic cluster A1240 at z=0.195. Our Subaru-based weak lensing analysis detects three mass clumps forming a ~4 Mpc filamentary structure elongated in the north-south orientation. The northern (M200=2.61+0.51−0.60×1014M⊙) and middle (M200=1.09+0.34−0.43×1014M⊙) mass clumps separated by ~1.3 Mpc are associated with A1240 and co-located with the X-ray peaks and cluster galaxy overdensities revealed by Chandra and MMT/Hectospec observations, respectively. The southern mass clump (M200=1.78+0.44−0.55×1014M⊙), ~1.5 Mpc to the south of the middle clump, coincides with the galaxy overdensity in A1237, the A1240 companion cluster at z=0.194. Considering the positions, orientations, and polarization fractions of the double radio relics measured by the LOFAR study, we suggest that A1240 is a post-merger binary system in the returning phase with the time-since-collision ~1.7 Gyr. With the SDSS DR16 data analysis, we also find that A1240 is embedded in the much larger-scale (~80 Mpc) filamentary structure whose orientation is in remarkable agreement with the hypothesized merger axis of A1240.

https://arxiv.org/abs/2109.06879