Correcting the gravitational dipole direction for a partial sky survey

Abstract

. The gravitational dipole approach is suitable for measuring β, the velocity parameter scale and, consequently, fσ 8, the product of the cosmic growth rate, f, and the matter density fluctuation on scales of 8 Mpc/h, σ 8. In cosmology, measurements of fσ 8 are important because they are a powerful tool for constraining alternative gravity models. However, in gravitational dipole analyses, if one uses a survey with incomplete sky coverage, this will certainly bias the measurement of the direction and magnitude of the dipole, which must be corrected accordingly. In this work we follow a new approach developed in ref. [1] to correct gravitational dipole measurements for partial sky data. Specifically, we study the gravitational dipole direction, important information to obtain an unbiased value of β. Our results show that, when comparing the velocity of the Local Group with the gravitational dipole, the correction procedure can actually recover the dipole direction with great precision, ensuring a robust result for β.