What do gas-rich galaxies actually tell us about modified Newtonian dynamics?

TL;DR

This paper critically examines claims that the baryonic Tully-Fisher relation supports modified Newtonian dynamics over cold dark matter, finding that current data and interpretations are inconsistent and unreliable for testing these theories.

Contribution

The study provides a comprehensive critique of recent claims supporting MOND using the BTFR, highlighting data inconsistencies and the oversimplification of CDM predictions.

Findings

Data scatter conflicts with observational uncertainties

BTFR measurements are highly discrepant across studies

CDM predictions oversimplify galaxy physics

Abstract

It has recently been claimed that measurements of the baryonic Tully-Fisher relation (BTFR), a power-law relationship between the observed baryonic masses and outer rotation velocities of galaxies, support the predictions of modified Newtonian dynamics for the slope and scatter in the relation, while challenging the cold dark matter (CDM) paradigm. We investigate these claims, and find that: 1) the scatter in the data used to determine the BTFR is in conflict with observational uncertainties on the data; 2) these data do not make strong distinctions regarding the best-fit BTFR parameters; 3) the literature contains a wide variety of measurements of the BTFR, many of which are discrepant with the recent results; and 4) the claimed CDM "prediction" for the BTFR is a gross oversimplification of the complex galaxy-scale physics involved. We conclude that the BTFR is currently untrustworthy as a test of CDM.