The Importance of Secondary Halos for Strong Lensing in Massive Galaxy Clusters across Redshift

Journal Article · 20 June 2019 · The Astrophysical Journal (Online)

DOI: https://doi.org/10.3847/1538-4357/ab1f74 · OSTI ID:1573368

Li, Nan  ^[1]; Gladders, Michael D. ^[2]; Heitmann, Katrin  ^[3]; Rangel, Esteban M. ^[4]; Child, Hillary L.  ^[5]; Florian, Michael K.  ^[6]; Bleem, Lindsey E. ^[5]; Habib, Salman ^[3]; Finkel, Hal J. ^[4]

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1. Univ. of Nottingham, Univ. Park (United Kingdom); Univ. of Chicago, IL (United States); Argonne National Lab. (ANL), Lemont, IL (United States)
2. Univ. of Chicago, IL (United States)
3. Argonne National Lab. (ANL), Lemont, IL (United States)
4. Argonne National Lab. (ANL), Lemont, IL (United States). Argonne Leadership Computing Facility (ALCF)
5. Argonne National Lab. (ANL), Lemont, IL (United States); Univ. of Chicago, IL (United States)
6. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)

Cosmological cluster-scale strong gravitational lensing probes the mass distribution of the dense cores of massive dark matter halos and the structures along the line of sight from background sources to the observer. It is frequently assumed that the primary lens mass dominates the lensing, with the contribution of secondary masses along the line of sight being neglected. Secondary mass structures may, however, affect both the detectability of strong lensing in a given survey and modify the properties of the lensing that is detected. This paper focuses on the former. Herein we utilize a large cosmological N-body simulation and a multiple lens plane (and many-source plane) ray-tracing technique to quantify the influence of line-of-sight structures on the detectability of cluster-scale strong lensing in a cluster sample with a mass limit that encompasses current cluster catalogs from the South Pole Telescope. We extract both primary and secondary halos from the “Outer Rim” simulation and consider two strong lensing realizations—one with only the primary halos included, and the other with the full mass light cone for each primary halo, including all secondary halos down to a mass limit more than an order of magnitude smaller than the smallest primary halos considered. In both cases, we use the same source information extracted from the Hubble Ultra Deep Field, and create realistic lensed images consistent with moderately deep ground-based imaging; the statistics of the observed strong lensing are extracted from these simulated images. The results demonstrate that down to the mass limit considered the total number of lenses is boosted by ~13%–21% when considering the complete multi-halo light cone; the enhancement is insensitive to different length-to-width cuts applied to the lensed arcs. The increment in strong lens counts peaks at lens redshifts of $$z$$ ~ 0.6 with no significant effect at $$z$$ < 0.3. The strongest trends are observed relative to the primary halo mass, with no significant effect in the most massive quintile of the halo sample, but increasingly boosting the observed lens counts toward small primary halo masses, with an enhancement greater than 50% in the least massive quintile of the halo masses considered.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States). Argonne Leadership Computing Facility (ALCF)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP); University of Chicago; Science and Technology Facilities Council (STFC); National Science Foundation (NSF); National Aeronautics and Space Administration (NASA); Kavli Foundation
• Grant/Contract Number: AC02-06CH11357; DGE-1144082; DGE-1746045; NSF PHY- 91125897
• OSTI ID: 1573368
• Journal Information: The Astrophysical Journal (Online), Vol. 878, Issue 2; ISSN 1538-4357
• Publisher: Institute of Physics (IOP)Copyright Statement
• Country of Publication: United States
• Language: English