Journal Article

Reducing distance errors for standard candles and standard sirens with weak-lensing shear and flexion maps

Stefan Hilbert, Jonathan R. Gair and Lindsay J. King

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 412, issue 2, pages 1023-1037
Published in print April 2011 | ISSN: 0035-8711
Published online March 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17963.x
Reducing distance errors for standard candles and standard sirens with weak-lensing shear and flexion maps

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Gravitational lensing induces significant errors in the measured distances to high-redshift standard candles and standard sirens such as Type Ia supernovae, gamma-ray bursts and merging supermassive black hole binaries. There will therefore be a significant benefit from correcting for the lensing error by using independent and accurate estimates of the lensing magnification. Here, we investigate how accurately the magnification can be inferred from convergence maps reconstructed from galaxy shear and flexion data. We employ ray-tracing through the Millennium Simulation (MS) to simulate lensing observations in large fields, and perform a weak-lensing reconstruction on the simulated fields. We identify optimal ways to filter the reconstructed convergence maps and to convert them to magnification maps, and analyse the resulting relation between the estimated and true magnification for sources at redshifts zS= 1 to 5. We find that a deep shear survey with 100 galaxies arcmin−2 can help to reduce the lensing-induced distance errors for standard candles/sirens at redshifts zS≈ 1.5 (zS≈ 5) on average by 20 per cent (10 per cent), whereas a futuristic survey with shear and flexion estimates from 500 galaxies arcmin−2 yields much larger reductions of 50 per cent (35 per cent). For redshifts zS≥ 3, a further improvement by ∼5 per cent can be achieved, if the individual redshifts of the galaxies are used in the reconstruction. Moreover, the reconstruction allows one to identify regions for which the convergence is low, and in which an error reduction by up to 75 per cent can be achieved. Such strongly reduced magnification uncertainties will greatly improve the value of high-redshift standard candles/sirens as cosmological probes.

Keywords: gravitational lensing: weak; gravitational waves; gamma-ray burst: general; supernovae: general; distance scale

Journal Article.  10258 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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