Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: HI Kinematics, Mass Distribution, and Star Formation Threshold in NGC
  6822, using the SKA pathfinder KAT-7   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$\alpha$
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.

1
The categories of this paper are: cs
16
The categories of this paper are: stat
3
The categories of this paper are: physics
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol