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Dipolar modulation in the size of galaxies: the effect of Doppler magnification

Bonvin, Camille and Andrianomena, Sambatra and Bacon, David and Clarkson, Chris and Maartens, Roy and Moloi, Teboho and Bull, Philip (2017) Dipolar modulation in the size of galaxies: the effect of Doppler magnification. Monthly Notices of the Royal Astronomical Society, 472 (4). pp. 3936-3951. ISSN 0035-8711. doi:10.1093/mnras/stx2049.

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Objects falling into an overdensity appear larger on its near side and smaller on its far side than other objects at the same redshift. This produces a dipolar pattern of magnification, primarily as a consequence of the Doppler effect. At low redshift, this Doppler magnification completely dominates the usual integrated gravitational lensing contribution to the lensing magnification. We show that one can optimally observe this pattern by extracting the dipole in the cross-correlation of number counts and galaxy sizes. This dipole allows us to almost completely remove the contribution from gravitational lensing up to redshift ≲0.5, and even at high redshift z ≃ 1, the dipole picks up the Doppler magnification predominantly. Doppler magnification should be easily detectable in current and upcoming optical and radio surveys; by forecasting for telescopes such as the SKA, we show that this technique is competitive with using peculiar velocities via redshift-space distortions to constrain dark energy. It produces similar yet complementary constraints on the cosmological model to those found using measurements of the cosmic shear.

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Additional Information:© 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 August 8. Received 2017 July 27; in original form 2016 October 21. Published: 12 August 2017. It is a pleasure to thank Elisa Chisari for interesting discussions. CB acknowledges support by the Swiss National Science Foundation. DB and RM are supported by the STFC (UK, Grant ST/K00090X/1). SA and RM are supported by the South African SKA Project. RM is also supported by the NRF (South Africa). PB’s research was supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, California Institute of Technology, administered by Universities Space Research Association under contract with NASA.
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)UNSPECIFIED
Science and Technology Facilities Council (STFC)ST/K00090X/1
South African Square Kilometre Array ProjectUNSPECIFIED
National Research Foundation of South AfricaUNSPECIFIED
NASA Postdoctoral ProgramUNSPECIFIED
Subject Keywords:large-scale structure of Universe
Issue or Number:4
Record Number:CaltechAUTHORS:20171211-110752487
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Official Citation:Camille Bonvin, Sambatra Andrianomena, David Bacon, Chris Clarkson, Roy Maartens, Teboho Moloi, Philip Bull; Dipolar modulation in the size of galaxies: the effect of Doppler magnification, Monthly Notices of the Royal Astronomical Society, Volume 472, Issue 4, 21 December 2017, Pages 3936–3951,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83799
Deposited By: Tony Diaz
Deposited On:12 Dec 2017 22:14
Last Modified:15 Nov 2021 20:14

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