Journal
ASTROPHYSICAL JOURNAL
Volume 823, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/0004-637X/823/1/37
Keywords
dark matter; gravitational lensing: strong
Categories
Funding
- NASA through Hubble Fellowship - Space Telescope Science Institute [HST-HF2-51358.001-A]
- NASA [NAS 5-26555, NNX12AD02G]
- NSF [AST-1212195, PLR-1248097, PHY-0114422]
- Sloan Fellowship
- Institute for Advanced Study
- Ambrose Monell Foundation
- Center for Advanced Study at UIUC
- U.S. National Science Foundation [AST-1312950]
- U.S. Department of Energy [DE-AC02-76SF00515]
- Weiland Family Stanford Graduate Fellowship
- Office of Science of the Department of Energy [DE-AC05-00OR22725]
- National Science Foundation [ACI-1053575, OCI-0725070, ACI-1238993]
- state of Illinois
- NASA [52865, NNX12AD02G] Funding Source: Federal RePORTER
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1312950] Funding Source: National Science Foundation
- Directorate For Geosciences
- Office of Polar Programs (OPP) [1248097] Funding Source: National Science Foundation
- Division Of Physics
- Direct For Mathematical & Physical Scien [1125897] Funding Source: National Science Foundation
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We study the abundance of substructure in the matter density near galaxies using ALMA Science Verification observations of the strong lensing system SDP. 81. We present a method to measure the abundance of subhalos around galaxies using interferometric observations of gravitational lenses. Using simulated ALMA observations we explore the effects of various systematics, including antenna phase errors and source priors, and show how such errors may be measured or marginalized. We apply our formalism to ALMA observations of SDP. 81. We find evidence for the presence of a M = 10(8.96 +/- 0.12)M(circle dot) subhalo near one of the images, with a significance of 6.9 sigma in a joint fit to data from bands 6 and 7; the effect of the subhalo is also detected in both bands individually. We also derive constraints on the abundance of dark matter (DM) subhalos down to M similar to 2 x 10(7) M-circle dot, pushing down to the mass regime of the smallest detected satellites in the Local Group, where there are significant discrepancies between the observed population of luminous galaxies and predicted DM subhalos. We find hints of additional substructure, warranting further study using the full SDP. 81 data set (including, for example, the spectroscopic imaging of the lensed carbon monoxide emission). We compare the results of this search to the predictions of Lambda CDM halos, and find that given current uncertainties in the host halo properties of SDP. 81, our measurements of substructure are consistent with theoretical expectations. Observations of larger samples of gravitational lenses with ALMA should be able to improve the constraints on the abundance of galactic substructure.
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