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29th of September 2022
Gas dynamics and star formation in NGC 6822
by Park et al.
Park et al. present HI (neutral hydrogen) gas kinematics and star formation activity in NGC 6822, a dwarf galaxy located in our Local Group of galaxies at a distance of 1.6 million light-years (490 kilo-parsecs). They performed profile decomposition of line-of-sight velocity profiles of archival HI data taken with the Australia Telescope Compact Array (ATCA). The large HI gas disk of the galaxy with a major axis of ~1 degree was observed through a mosaic of eight pointings with the ATCA. The top left panel above shows a multi-wavelength color-composite image of NGC 6822 using the integrated flux density map from ATCA HI 21cm (gray), GALEX FUV (blue), and WISE 22 ┬Ám (yellow) data. The top right, bottom left, and bottom right panels show "moment" maps: moment0 shows the integrated flux density, moment1 the intensity-weighted mean velocity, and moment2 the intensity-weighted velocity dispersion. Two notable features in the HI gas distribution of NGC 6822 (the moment0 map) are the companion HI cloud located in the northwestern (top-right) region of the galaxy, and the supergiant HI shell occupying a large area of the disk in the southeastern region. The team used a new tool to classify the decomposed HI gas components of NGC 6822 into cool-bulk, warm-bulk, cool-non-bulk and warm-non-bulk motions with respect to their centroid velocities and velocity dispersions.

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