# Possible origins of anomalous H$\,$I gas around MHONGOOSE galaxy, NGC 5068

**Authors:** J. Healy, W. J. G. de Blok, F. M. Maccagni, P. Amram, L. Chemin, F. Combes, B. W. Holwerda, P. Kamphuis, D. J. Pisano, E. Schinnerer, K. Spekkens, L. Verdes-Montenegro, F. Walter, E. A. K. Adams, B. K. Gibson, D. Kleiner, S. Veronese, N. Zabel, J. English, C. Carignan  
**arXiv:** [2402.13749](https://arxiv.org/abs/2402.13749)  
**Date:** 2024-02-21  
**Summary page:** https://www.summarizepaper.com/en/paper/2402.13749v1/

## Key points

- Investigated anomalous neutral atomic hydrogen gas (H$\,$I) around NGC 5068 using deep H$\,$I observations with MeerKAT
- Existing H$\,$I reservoirs in galaxies are insufficient to sustain observed star formation levels without replenishment
- Regularly rotating inner disk aligned with main star-forming disk
- Warped outer disk with low column density gas
- Clumps of gas on north-west side of galaxy
- Identified anomalous gas deviating from galaxy's main rotation, suggesting possible extra-galactic origin
- Explored scenarios and concluded fresh accretion as most likely explanation for anomalous gas presence
- High sensitivity and resolution of MeerKAT data detected low column density H$\,$I around NGC 5068 down to N$_{\rm{H\,I}} = 6.4 \times 10^{17}\,$cm$^{-2}$ at 90$''$ resolution over a $20\,$km/s linewidth
- Detailed analysis sheds light on dynamics and origins of H$\,$I gas in galaxies, contributing to understanding processes like accretion fueling star formation activities and how galaxies evolve through interactions with surrounding environment

## Summary

In this study, we investigate the presence of anomalous neutral atomic hydrogen gas (H$\,$I) around the star-forming galaxy NGC 5068 using deep H$\,$I observations obtained with MeerKAT as part of the MHONGOOSE survey. The existing reservoirs of H$\,$I in galaxies are insufficient to sustain observed levels of star formation without replenishment. Our data reveal a complex morphology and kinematics of H$\,$I in NGC 5068, including a regularly rotating inner disk aligned with the main star-forming disk, a warped outer disk with low column density gas, and clumps of gas on the north-west side of the galaxy. By employing a two-disk model to describe the inner and outer disks, we identify anomalous gas that deviates from the galaxy's main rotation. The morphology and kinematics suggest a possible extra-galactic origin for this anomalous gas. We explore various scenarios to explain its presence and conclude that fresh accretion is the most likely explanation. The high sensitivity and resolution of our MeerKAT data allow us to detect low column density H$\,$I around NGC 5068 down to N$_{\rm{H\,I}} = 6.4 \times 10^{17}\,$cm$^{-2}$ at 90$''$ resolution over a $20\,$km/s linewidth. This detailed analysis provides valuable insights into the dynamics and origins of H$\,$I gas in galaxies, shedding light on processes such as accretion that contribute to fueling star formation activities. Our findings contribute to a better understanding of how galaxies evolve over time through interactions with their surrounding environment.