We present high sensitivity HI observations of NGC 6822, obtained with the Karoo Array Telescope (KAT-7). We study the kinematics, the mass distribution, and the star formation thresholds. The KAT-7 short baselines and low system temperature make it sensitive to large-scale, low surface brightness emission. The observations detected $\sim$ 23$\%$ more flux than previous ATCA observations. We fit a tilted ring model to the HI velocity field to derive the rotation curve (RC). The KAT-7 observations allow the measurement of the rotation curve of NGC 6822 out to 5.8 kpc, $\sim$ 1 kpc further than existing measurements.
NGC 6822 is seen to be dark matter dominated at all radii. The observationally motivated pseudo-isothermal dark matter (DM) halo model reproduces well the observed RC while the Navarro Frank-White DM model gives a poor fit to the data. We find the best fit mass to light ratio (M/L) of 0.12 $\pm$ 0.01 which is consistent with the literature. The Modified Newtonian Dynamics (MOND) gives a poor fit to our data.
We derive the star formation threshold in NGC 6822 using the HI and H$α$ data. The critical gas densities were calculated for gravitational instabilities using the Toomre-Q criterion and the cloud-growth criterion. We found that in regions of star formation, the cloud-growth criterion explains star formation better than the Toomre-Q criterion. This shows that the local shear rate could be a key player in cloud formation for irregular galaxies such as NGC 6822.
Carbon chain diversity in L1544 and IRAS 16293-2422: an astrochemical pathfinder study for the SKAO
INAF, Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所，阿切尔西天文台）；National Radio Astronomy Observatory（美国国家射电天文台）；Univ. Grenoble Alpes, CNRS, IPAG（格勒诺布尔阿尔卑斯大学，法国国家科学研究中心，行星与地球物理学研究所）；European Southern Observatory（欧洲南方天文台）；Dipartimento di Chimica, Biologia e Biotecnologie（化学、生物与生物技术系）；Department of Chemistry, University of Virginia（弗吉尼亚大学化学系）；Department of Astronomy, University of Virginia（弗吉尼亚大学天文学系）；Université du Rennes, CNRS, IPR (Institut de Physique de Rennes)UMR 6251（雷恩大学，法国国家科学研究中心，雷恩物理研究所）
University of Alberta（阿尔伯塔大学）；Ludwig Maximilian University of Munich (LMU)（慕尼黑大学）；The University of Western Australia（西澳大学）；University of the Witwatersrand（威特沃特斯兰德大学）；NASA Ames Research Center（美国国家航空航天局艾姆斯研究中心）；Cardiff University（卡迪夫大学）；University Catholic of Lyon（里昂天主教大学）
Rhodes University（罗德斯大学）；Queen’s University（女王大学）；Arthur B. McDonald Canadian Astroparticle Physics Research Institute, Queen’s University（亚瑟·B·麦克唐纳加拿大高能粒子物理研究所，女王大学）；IFPU – Institute for Fundamental Physics of the Universe（宇宙基础物理研究所 (IFPU)）；Seoul National University（首尔大学）；The University of Western Australia（西澳大学）
