Iras-allsky

Multiwavelength Analysis of A1240, the Double Radio-relic Merging Galaxy Cluster Embedded in an 80 Mpc-long Cosmic Filament

January 2022 • 2022ApJ...925...68C

Authors • Cho, Hyejeon • James Jee, M. • Smith, Rory • Finner, Kyle • Lee, Wonki

Abstract • 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 an ~4 Mpc filamentary structure elongated in a north-south orientation. The northern ( ${M}_{200}={2.61}_{-0.60}^{+0.51}\times {10}^{14}{M}_{\odot }$ ) and middle ( ${M}_{200}={1.09}_{-0.43}^{+0.34}\times {10}^{14}{M}_{\odot }$ ) mass clumps separated by ~1.3 Mpc are associated with A1240 and colocated with the X-ray peaks and cluster galaxy overdensities revealed by Chandra and MMT/Hectospec observations, respectively. The southern mass clump ( ${M}_{200}={1.78}_{-0.55}^{+0.44}\times {10}^{14}{M}_{\odot }$ ), ~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 postmerger binary system in the returning phase with a time since collision of ~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.

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Kyle Finner

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