Fast and spurious: a robust determination of our peculiar velocity with future galaxy surveys
arxiv(2024)
Abstract
To date, the most precise measurement of the observer's peculiar velocity
comes from the dipole in the Cosmic Microwave Background (CMB). This velocity
also generates a dipole in the source number counts, whose amplitude is
governed not only by the observer velocity, but also by specific properties of
the sources, that are difficult to determine precisely. Quantitative studies of
the source number counts currently give dipoles which are reasonably well
aligned with the CMB dipole, but with a significantly larger amplitude than
that of the CMB dipole. In this work, we explore an alternative way of
measuring the observer velocity from the source number counts, using
correlations between neighboring spherical harmonic coefficients, induced by
the velocity. We show that these correlations contain both a term sensitive to
the source properties and another one directly given by the observer velocity.
We explore the potential of a Euclid-like survey to directly measure this
second contribution, independently of the characteristics of the population of
sources. We find that the method can reach a precision of 4
a detection significance of 24 sigma, on the observer velocity. This will
settle with precision the present "dipole tension".
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