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Title: Observation of Small Scale Structure Using Sextupole Lensing

Abstract

Weak gravitational lensing seeks to determine shear by measuring induced quadrupole (elliptical) shapes in background galaxy images. Small impact parameter (a few kpc) gravitational lensing by foreground core masses between 210{sup 9} and 210{sup 12}M{circle_dot} will additionally induce a sextupole shape with the quadrupole and sextupole minima aligned. This correlation in relative orientation of the quadrupole and sextupole provides a sensitive method to identify images which have been slightly curved by lensing events. A general theoretical framework for sextupole lensing is developed which includes several low order coefficients in a general lensing map. Tools to impute map coefficients from the galaxy images are described and applied to the north Hubble deep field. Instrumental PSFs, camera charge diffusion, and image composition methods are modeled in the coefficient determination process. Estimates of Poisson counting noise for each galaxy are used to cut galaxies with signals too small to reliably establish curvature. Curved galaxies are found to be spatially clumped, as would be expected if the curving were due to small impact parameter lensing by localized ensembles of dark matter haloes. Simulations provide an estimate of the total required lensing mass and the acceptable mass range of the constituent haloes. The overdensities andmore » underdensities of visible galaxies and their locations in the Hubble foreground is found to be consistent with our observations and their interpretation as lensing events.« less

Authors:
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
839839
Report Number(s):
SLAC-PUB-11102
TRN: US200516%%414
DOE Contract Number:  
AC02-76SF00515
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CAMERAS; DIFFUSION; GALAXIES; IMPACT PARAMETER; NONLUMINOUS MATTER; ORIENTATION; QUADRUPOLES; SHAPE; SHEAR

Citation Formats

Irwin, J. Observation of Small Scale Structure Using Sextupole Lensing. United States: N. p., 2005. Web. doi:10.2172/839839.
Irwin, J. Observation of Small Scale Structure Using Sextupole Lensing. United States. https://doi.org/10.2172/839839
Irwin, J. 2005. "Observation of Small Scale Structure Using Sextupole Lensing". United States. https://doi.org/10.2172/839839. https://www.osti.gov/servlets/purl/839839.
@article{osti_839839,
title = {Observation of Small Scale Structure Using Sextupole Lensing},
author = {Irwin, J},
abstractNote = {Weak gravitational lensing seeks to determine shear by measuring induced quadrupole (elliptical) shapes in background galaxy images. Small impact parameter (a few kpc) gravitational lensing by foreground core masses between 210{sup 9} and 210{sup 12}M{circle_dot} will additionally induce a sextupole shape with the quadrupole and sextupole minima aligned. This correlation in relative orientation of the quadrupole and sextupole provides a sensitive method to identify images which have been slightly curved by lensing events. A general theoretical framework for sextupole lensing is developed which includes several low order coefficients in a general lensing map. Tools to impute map coefficients from the galaxy images are described and applied to the north Hubble deep field. Instrumental PSFs, camera charge diffusion, and image composition methods are modeled in the coefficient determination process. Estimates of Poisson counting noise for each galaxy are used to cut galaxies with signals too small to reliably establish curvature. Curved galaxies are found to be spatially clumped, as would be expected if the curving were due to small impact parameter lensing by localized ensembles of dark matter haloes. Simulations provide an estimate of the total required lensing mass and the acceptable mass range of the constituent haloes. The overdensities and underdensities of visible galaxies and their locations in the Hubble foreground is found to be consistent with our observations and their interpretation as lensing events.},
doi = {10.2172/839839},
url = {https://www.osti.gov/biblio/839839}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Apr 15 00:00:00 EDT 2005},
month = {Fri Apr 15 00:00:00 EDT 2005}
}