Weak lensing with sizes, magnitudes and shapes
File(s)
Published version
Author(s)
Alsing, J
Kirk, D
Heavens, A
Jaffe, AH
Type
Journal Article
Abstract
Weak lensing can be observed through a number of effects on the images of distant galaxies; their shapes are sheared, sizes and fluxes (magnitudes) are magnified and positions on the sky are modified by the lensing field. Galaxy shapes probe the shear field whilst size, magnitude and number density probe the convergence field. Both contain cosmological information. In this paper, we are concerned with the magnification of sizes and magnitudes of individual galaxies as a probe of cosmic convergence. We develop a Bayesian approach for inferring the convergence field from measured sizes, magnitudes and redshifts and demonstrate that this inference requires detailed knowledge of the joint distribution of intrinsic sizes and magnitudes. We build a simple parametrized model for the size–magnitude distribution and estimate this distribution for CFHTLenS galaxies. In light of the measured distribution, we show that the typical dispersion on convergence estimation is ∼0.8, compared to ∼0.38 for shear. We discuss the possibility of physical systematics for magnification (similar to intrinsic alignments for shear) and compute the expected gains in the dark energy figure-of-merit (FoM) from combining magnification with shear for different scenarios regarding systematics: accounting for intrinsic alignments but no systematics for magnification, including magnification could improve the FoM by up to a factor of ∼2.5, whilst when accounting for physical systematics in both shear and magnification we anticipate a gain between ∼25 and ∼65 per cent. The fact that shear and magnification are subject to different systematics makes magnification an attractive complement to any cosmic shear analysis.
Date Issued
2015-07-14
Date Acceptance
2015-06-02
Citation
Monthly Notices of the Royal Astronomical Society, 2015, 452 (2), pp.1202-1216
ISSN
1365-2966
Publisher
Oxford University Press
Start Page
1202
End Page
1216
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
452
Issue
2
Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2015 The Royal Astronomical Society. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Sponsor
Imperial College Trust
Science and Technology Facilities Council (STFC)
Grant Number
N/A
ST/K001051/1
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
gravitational lensing: weak
DIGITAL SKY SURVEY
INTRINSIC ELLIPTICITY CORRELATION
MORPHOLOGY-DENSITY RELATION
LUMINOUS RED GALAXIES
DARK-MATTER HALOES
COSMIC SHEAR
GRAVITATIONAL SHEAR
REDSHIFT SURVEY
POWER SPECTRA
ALIGNMENTS
0201 Astronomical And Space Sciences
Publication Status
Published