Large-scale collective motion of RFGC galaxies in curved space-time

TL;DR

This study investigates the large-scale collective motion of flat edge-on spiral galaxies considering space-time curvature effects, finding that relativistic corrections have minimal impact and the observed velocities align with ΛCDM predictions.

Contribution

It extends the analysis of galaxy motions by incorporating relativistic effects and evaluates their significance using simulations, confirming consistency with standard cosmological models.

Findings

Relativistic effects minimally alter the velocity field.

Measurement errors can significantly influence parameter estimates.

Bulk flow velocities agree with ΛCDM cosmology.

Abstract

We consider large-scale collective motion of flat edge-on spiral galaxies from the Revised Flat Galaxy Catalogue (RFGC) taking into account the curvature of space-time in the Local Universe at the scale 100 Mpc/h. We analyse how the relativistic model of collective motion should be modified to provide the best possible values of parameters, the effects that impact these parameters and ways to mitigate them. Evolution of galactic diameters, selection effects, and difference between isophotal and angular diameter distances are inadequate to explain this impact. At the same time, measurement error in HI line widths and angular diameters can easily provide such an impact. This is illustrated in a toy model, which allows analytical consideration, and then in the full model using Monte Carlo simulations. The resulting velocity field is very close to that provided by the non-relativistic model of motion. The obtained bulk flow velocity is consistent with {\Lambda}CDM cosmology.