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Title: Detection of Lensing Substructure Using Alma Observations of the Dusty Galaxy SDP.81

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 = 108.96±0.12 M subhalo near one of the images, with a significance of 6.9σ 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 ~ 2 × 107 M, 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 carbonmore » monoxide emission). We compare the results of this search to the predictions of ΛCDM halos, and find that given current uncertainties in the host halo properties of SDP.81, our measurements of substructure are consistent with theoretical expectations. Finally, observations of larger samples of gravitational lenses with ALMA should be able to improve the constraints on the abundance of galactic substructure.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [1] ;  [5] ;  [4] ;  [6] ;  [7] ;  [8] ;  [5] ;  [9] ;  [10] ;  [1] ;  [5] ;  [4]
  1. Stanford Univ., CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology and Dept. of Physics
  2. Univ. of Illinois, Urbana-Champaign, IL (United States). Astronomy Dept.; Inst. for Advanced Study, Princeton, NJ (United States). School of Natural Sciences; Univ. of Tokyo (Japan). Kavli Institute for the Physics and Mathematics of the universe, TODIAS; Univ. of Kwa-Zulu Natal, KwaZulu-Natal (South Africa)
  3. Univ. of Arizona, Tucson, AZ (United States). Steward Observatory
  4. Stanford Univ., CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology and Dept. of Physics; SLAC National Accelerator Lab., Menlo Park, CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology and Dept. of Particle Physics and Astrophysics
  5. Univ. of Illinois, Urbana-Champaign, IL (United States). Astronomy Dept.
  6. Univ. of Chicago, IL (United States). Kavli Inst. for Cosmological Physics (KICP)
  7. Univ. of California, Davis, CA (United States). Dept. of Physics
  8. McGill Univ., Montreal, QC (Canada). Dept of Physics
  9. SLAC National Accelerator Lab., Menlo Park, CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology and Dept. of Particle Physics and Astrophysics
  10. Univ. of Toronto, ON (Canada). Canadian Inst. for Theoretical Astrophysics
Publication Date:
OSTI Identifier:
1280817
Grant/Contract Number:
AC02-76SF00515; HST-HF2-51358.001-A; NAS 5-26555; AST-1212195; NNX12AD02G; AST-1312950; PLR-1248097; PHY-0114422; AC05-00OR22725; ACI-1053575; OCI-0725070; ACI-1238993
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 823; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
NASA; USDOE; US National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS dark matter; gravitational lensing: strong