Early Observations of the MHONGOOSE Galaxies: Getting Ready for MeerKAT

TL;DR

This paper reports early observations of 20 galaxies from the MHONGOOSE survey using KAT-7, GBT, and MeerKAT, focusing on calibration, gas accretion, and detailed rotation curve analysis to compare dark matter models and MOND.

Contribution

It provides the first detailed rotation curves and mass models for two galaxies using MeerKAT data, and compares dark matter models with MOND, demonstrating the effectiveness of pseudo-isothermal models.

Findings

No signs of gas accretion detected down to specified column density levels.

Dark matter models fit the rotation curves better than MOND.

Pseudo-isothermal model is most consistent with observed data.

Abstract

We present early observations of 20 galaxies in the MHONGOOSE survey galaxies using KAT-7, the GBT, and MeerKAT. We present the best calibrators for five of the MHONGOOSE galaxies observed with the KAT-7, and search for signs of gas accretion in the GBT data, down to $3\sigma$ column density levels of $\rm 2.2\times10^{18}\, cm^{-2}$ over a $\rm 20\, km\, s^{-1}$ linewidth, but identify none. Using the KAT-7 and MeerKAT data, we have derived rotation curves and mass models for NGC 3621 and NGC 7424 out to an unprecedented extent. As a precursor to the SKA, the MeerKAT telescope combines both a high spatial resolution and a large field of view, necessary to map the extended neutral hydrogen in local galaxies. The mass models of the two galaxies were constructed for both the Dark Matter (DM) models (the pseudo-isothermal model and the Navarro-Frenk-White model) and MOND. Overall, we find that the DM models provide a better fit than MOND to the galaxies' rotation curves. Furthermore, the pseudo-isothermal model is found to be the most consistent with the observations.