## “School of Astronomy”

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Paper   IPM / Astronomy / 13925
School of Astronomy
Title:   Peculiar velocity measurement in a clumpy universe
Author(s):
 1 F. Habibi 2 S. Baghram 3 S. Tavasoli
Status:   Published
Journal: Astronomy & Astrophysics
Year:  2016
Pages:   7
Supported by:            IPM IPM
Abstract:
At low redshifts, deviations of the measured luminosity distance from the background FRW universe can be attributed to peculiar velocities of galaxies. Via observing the cosmic standard candles, this is one of the conventional ways to estimate peculiar velocities. However, at intermediate redshifts (z > 0.5), deviations from the background FRW model are not uniquely governed by peculiar velocities. Luminosity distances are modified by gravitational lensing which affects the light trajectories. Hence using the conventional peculiar velocity method will result in an overestimate of the measured peculiar velocities at intermediate redshifts. Here we quantify this effect and show that although present data are still incapable of extracting any lensing effect on distance measurement and peculiar velocity estimation, this effect will however be significant for future large-scale structure surveys.