Józsa, G. I. G., Jarrett, T. H., Cluver, M. E., Wong, O. I., Havenga, O., Yao, H. F. M., Marchetti, L., Taylor, E. N., Kamphuis, P., Maccagni, F. M., Ramaila, A. J. T., Serra, P., Smirnov, O. M., White, S. V., Kilborn, V., Holwerda, B. W., Hopkins, A. M., Brough, S., Pimbblet, K. A., and Driver, S. P.
We report on the detection of a large, extended H i cloud complex in the Galaxy and Mass Survey G23 field, located at a redshift of z ∼ 0.03, observed as part of the MeerKAT Habitat of Galaxies Survey campaign (a pilot survey to explore the mosaicing capabilities of the MeerKAT telescope). The cloud complex, with a total mass of 1010.0M⊙, lies in proximity to a large galaxy group with Mdyn ∼ 1013.5M⊙. We identify seven H ɪ peak concentrations, interconnected as a tenuous chain structure, extending ∼400 kpc from east to west, with the largest (central) concentration containing 109.7M⊙ in H ɪ gas distributed across 50 kpc. The main source is not detected in ultraviolet, optical, or infrared imaging. The implied gas mass-to-light ratio (MH I/Lr) is extreme (>1000) even in comparison to other dark clouds. The complex has very little kinematic structure (110 km s−1), making it difficult to identify cloud rotation. Assuming pressure support, the total mass of the central concentration is > 1010.2M⊙, while a lower limit to the dynamical mass in the case of full rotational support is 1010.4M⊙. If the central concentration is a stable structure, it has to contain some amount of unseen matter, but potentially less than is observed for a typical galaxy. It is, however, not clear whether the structure has any gravitationally stable concentrations. We report a faint UV-optical-infrared source in proximity to one of the smaller concentrations in the gas complex, leading to a possible stellar association. The system nature and origins is enigmatic, potentially being the result of an interaction with or within the galaxy group it appears to be associated with. [ABSTRACT FROM AUTHOR]