Survey

The Survey

We observe a total of 30 galaxies, of various Hubble types, masses and inclinations. The sample is described here. We are achieving our desired goal to detect HI column densities of 1.25 · 10¹⁹ cm⁻² at 5σ over 16 km s⁻¹ at 30” resolution. At a resolution of ∼90", this enables detections at the ∼5 · 10¹⁷ cm⁻² level (3σ). By using stacking of HI profiles these limits can be lowered further. Optimal smoothing to 16 km s⁻¹ channels would increase sensitivities by a factor √(16/5).

The figure on this page compares the sensitivity of MHONGOOSE with those of existing HI surveys. It is clear that MHONGOOSE probes the low column densities in galaxies at resolutions that will only be surpassed by the SKA.

After an extensive commissioning period, observations started in October 2021 and are now well underway. The total observing time for the survey is 1650 hours which is equally divided over 30 galaxies, or 55 hours per galaxy. For each galaxy, this is again divided in 10 tracks of 5.5 hours, five of them rising tracks and five of them setting tracks. For all galaxies, at least one track has been collected and the survey observations are currently 2/3 complete.

The first internal team data release of full-depth data happened in December 2022. This consisted of data for the 10 galaxies for which full-depth data were available. Data cubes were released at different resolutions, along with the corresponding moment maps, and ancillary data.

A number of papers based on the first deep data release are in progress. The commissioning data resulted in a number of commissioning reports (available on the SARAO website) and the scientific paper: de Blok, W.J.G. and 45 colleagues. 2020 on “MeerKAT HI commissioning observations of MHONGOOSE galaxy ESO 302-G014.”