THINGS about MOND

TL;DR

This study analyzes high-quality galactic rotation curves from THINGS to test MOND, finding that the simple interpolating function fits best and that the derived acceleration parameter aligns with previous estimates, supporting MOND's viability.

Contribution

The paper provides a detailed analysis of 12 galaxy rotation curves using MOND, confirming the consistency of the acceleration parameter and stellar mass-to-light ratios with prior findings and stellar models.

Findings

The simple interpolating function yields better fits than the standard one.

The median a0 value is consistent with previous studies.

MOND fits are excellent for 75% of the sample when distance is free.

Abstract

We present the analysis of 12 high-resolution galactic rotation curves from The HI Nearby Galaxy Survey (THINGS) in the context of modified Newtonian dynamics (MOND). These rotation curves were selected to be the most reliable for mass modelling, and they are the highest quality rotation curves currently available for a sample of galaxies spanning a wide range of luminosities. We fit the rotation curves with the "simple" and "standard" interpolating functions of MOND, and we find that the "simple" function yields better results. We also redetermine the value of a0, and find a median value very close to the one determined in previous studies, a0 = (1.22 +- 0.33) x 10^{-8} cm/s^2. Leaving the distance as a free parameter within the uncertainty of its best independently determined value leads to excellent quality fits for 75% of the sample. Among the three exceptions, two are also known to give relatively poor fits also in Newtonian dynamics plus dark matter. The remaining case (NGC 3198), presents some tension between the observations and the MOND fit, which might however be explained by the presence of non-circular motions, by a small distance, or by a value of a0 at the lower end of our best-fit interval, 0.9 x 10^{-8} cm/s^2. The best-fit stellar M/L ratios are generally in remarkable agreement with the predictions of stellar population synthesis models. We also show that the narrow range of gravitational accelerations found to be generated by dark matter in galaxies is consistent with the narrow range of additional gravity predicted by MOND.