An excess of small-scale gravitational lenses observed in galaxy clusters

Creators: Meneghetti, Massimo; Davoli, Guido; Bergamini, Pietro; Rosati, Piero; Natarajan, Priyamvada; Giocoli, Carlo; Caminha, Gabriel B.; Metcalf, R. Benton; Rasia, Elena; Borgani, Stefano; Calura, Francesco; Grillo, Claudio; Mercurio, Amata; Vanzella, Eros

Abstract

Cold dark matter (CDM) constitutes most of the matter in the Universe. The interplay between dark and luminous matter in dense cosmic environments, such as galaxy clusters, is studied theoretically using cosmological simulations. Observations of gravitational lensing are used to characterize the properties of substructures—the small-scale distribution of dark matter—in clusters. We derive a metric, the probability of strong lensing events produced by dark-matter substructure, and compute it for 11 galaxy clusters. The observed cluster substructures are more efficient lenses than predicted by CDM simulations, by more than an order of magnitude. We suggest that systematic issues with simulations or incorrect assumptions about the properties of dark matter could explain our results.

Additional Information

© 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works https://www.sciencemag.org/about/science-licenses-journal-article-reuse. This is an article distributed under the terms of the Science Journals Default License. Received for publication July 9, 2019. Accepted for publication July 27, 2020. We thank S. White and F. van den Bosch for insightful discussions. We also thank G. Murante for sharing the numerical simulations and A. Benitez-Llambay for making public his code PYSPHVIEWER. This work was performed in part at Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611. We acknowledge support from the Italian Ministry of Foreign Affairs and International Cooperation, Directorate General for Country Promotion, from PRIN-MIUR 2015W7KAWC, from PRIN-MIUR 2017WSCC32, from PRIN MIUR 2017-20173ML3WW_001, from ASI through grant ASI-INAF n. 2018-23-HH.0 and ASI-INAF n.2017-14-H.0, from INAF (funding of main-stream projects), and from the INFN INDARK grant. P.N. acknowledges support from the Aspen Center for Physics for the workshop titled "Progress after Impasse: New Frontiers in Dark Matter" in Summer 2019 and the Space Telescope Science Institute grant HST-GO-15117.021. C.G. acknowledges support by VILLUM FONDEN Young Investigator Programme through grant no. 10123. S.B. acknowledges financial support from the EU H2020 Research and Innovation Programme under the ExaNeSt project (grant agreement no. 671553). Author contributions: M.M. coordinated the project, performed the lensing analysis of the simulated clusters, measured the lensing cross sections and probabilities of both simulated halos and observed clusters, and contributed to the modeling of the observed clusters. G.D. developed the algorithm to measure the lensing cross sections. P.B., P.R., G.B.C., A.M., and C.G. built the strong lensing models and the spectroscopic catalogs of MACSJ1206, AS1063, and MACSJ0416 and of the "Gold" CLASH sample. C.G. performed the MOKA simulations of MACSJ1206 and analyzed the subhalo catalogs of the simulated clusters. P.N., F.C., and E.V. contributed to the analysis of the simulations and to the interpretation of the results. E.R. and S.B. produced the numerical simulations and the subhalo catalogs. R.B.M. produced the multilens plane simulations used to test effects of matter along the line of sight. M.M., P.N., and F.C. wrote the manuscript, including contributions from all the other authors. The authors declare no competing interests. Data and materials availability: Our simulation snapshots and simulated subhalo catalogs (both in GADGET file format), along with lens models for the clusters in the reference and CLASH Gold samples (as LENSTOOL parameter files), are available at https://dx.doi.org/10.20371/INAF/DS/2020_00001. The lens models of the clusters in the HFF sample were taken from https://archive.stsci.edu/prepds/frontier/lensmodels/; we used version v4 of the CATS and Sharon maps. The GLAMER software for ray-tracing and the code used to measure the GGSL cross sections are available at Zenodo (31, 32).

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Accepted Version - 2009.04471.pdf

Supplemental Material - aax5164_Meneghetti_SM.pdf

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