Arguments against using h^{1} Mpc units in observational cosmology
Abstract
It is common to express cosmological measurements in units of h^{1} Mpc . Here, we review some of the complications that originate from this practice. A crucial problem caused by these units is related to the normalization of the matter power spectrum, which is commonly characterized in terms of the lineartheory rms mass fluctuation in spheres of radius 8 h^{1} Mpc , σ_{8}. This parameter does not correctly capture the impact of h on the amplitude of density fluctuations. We show that the use of σ_{8} has caused critical misconceptions for both the socalled σ_{8} tension regarding the consistency between lowredshift probes and cosmic microwave background data and the way in which growthrate estimates inferred from redshiftspace distortions are commonly expressed. We propose to abandon the use of h^{1} Mpc units in cosmology and to characterize the amplitude of the matter power spectrum in terms of σ_{12}, defined as the mass fluctuation in spheres of radius 12 Mpc, whose value is similar to the standard σ_{8} for h ∼0.67 .
 Publication:

Physical Review D
 Pub Date:
 December 2020
 DOI:
 10.1103/PhysRevD.102.123511
 arXiv:
 arXiv:2002.07829
 Bibcode:
 2020PhRvD.102l3511S
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 6 pages, 4 figures. Minor changes. Matches version published in PRD