Cosmology with Doppler lensing

Abstract

Doppler lensing is the apparent change in object size and magnitude due to peculiar velocities. Objects falling into an overdensity appear larger on its near side, and smaller on its far side, than typical objects at the same redshifts. This effect dominates over the usual gravitational lensing magnification at low redshift. Doppler lensing is a promising new probe of cosmology, and we explore in detail how to utilize the effect with forthcoming surveys. We present cosmological simulations of the Doppler and gravitational lensing effects based on the Millennium simulation. We show that Doppler lensing can be detected around stacked voids or unvirialised over-densities. New power spectra and correlation functions are proposed which are designed to be sensitive to Doppler lensing. We consider the impact of gravitational lensing and intrinsic size correlations on these quantities. We compute the correlation functions and forecast the errors for realistic forthcoming surveys, providing predictions for constraints on cosmological parameters. Finally, we demonstrate how we can make 3-D potential maps of large volumes of the Universe using Doppler lensing.

Large-scale imprint of relativistic effects in the cosmic magnification

“…We see that at this epoch, the full (GR-corrected) power spectrum C is greater in power than the standard (lensing) power spectrum C std , by a factor C /C std ∼ 10 3 . This difference is mainly owing to the Doppler effect in C ; the Doppler term in ∆ obs M dominates at low z [20,25], which fluctuates on small 100. Our results are also in agreement with the work by [69] (see Fig.…”

“…For example, when a source is moving towards the observer its flux becomes magnified: this is Doppler effect, i.e. Doppler magnification (also referred to as "Doppler lensing" [25,26]). Time delay also causes magnification by broadening the observed flux.…”

“…(Throughout this work, the DE equation of state parameter w x is used as given by (26).) Note that given our consideration of C , which is evaluated at a fixed z, the sign of Q is irrelevant-see (24) and (25). However, care must be taken when considering the cross- (17)), while the blue line is the standard power spectrum C std containing only the weak lensing effect (i.e.…”

Modelling the impact of intrinsic size and luminosity correlations on magnification estimation

“…We then can use as our point estimators the following (Schmidt et al 2012;Heavens et al 2013;Bacon et al 2014):…”

Unraveling the nature of gravity through our clumpy universe

“…(III) in the case of modified gravity), doppler κ v (this is introduced due to the peculiar velocity of the source and observer), the Sachs-Wolfe (SW) effect κ SW and the Integrated Sachs-Wolfe (ISW) κ ISW (which are related to the difference in the amount of gravitational potential along the line of sight). Consequently, the perturbation terms δd L are [23]…”