Cosmic Mach Number: A Sensitive Probe for the Growth of Structure

TL;DR

This paper explores the Cosmic Mach Number as a tool to constrain cosmological models, demonstrating its sensitivity to structure growth and potential to distinguish between standard and alternative theories with future data.

Contribution

It introduces the use of the Cosmic Mach Number as a sensitive probe for structure growth, comparing observational data with cosmological models and highlighting its potential for future constraints.

Findings

Current data aligns with the WMAP7 LCDM model.

CMN is highly sensitive to structure growth on specific scales.

Future CMN measurements can differentiate between cosmological models.

Abstract

In this Letter, we investigate the potential power of the Cosmic Mach Number (CMN), which is the ratio between the mean velocity and the velocity dispersion of galaxies as a function of cosmic scales, to constrain cosmologies. We first measure the CMN from 5 catalogues of galaxy peculiar velocity surveys at low redshift (0.002<z<0.03), and use them to contrast cosmological models. Overall, current data is consistent with the WMAP7 LCDM model. We find that the CMN is highly sensitive to the growth of structure on scales 0.01<k<0.1 h/Mpc in Fourier space. Therefore, modified gravity models, and models with massive neutrinos, in which the structure growth generally deviates from that in the LCDM model in a scale-dependent way, can be well differentiated from the LCDM model using future CMN data.