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19th of August 2021
WALLABY observations of the Eridanus supergroup
by B-Q For et al.
For et al. present observations of the Eridanus supergroup obtained with the Australian Square Kilometre Array Pathfinder (ASKAP) as part of the pre-pilot survey for the Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY). The total number of detected neutral hydrogen (HI) sources is 55, of which 12 are background galaxies not associated with the Eridanus supergroup. The presence of distorted HI morphology in all detected galaxies suggests ongoing tidal interactions within the subgroups. In general, the majority of these galaxies are actively forming stars. The image above shows results for NGC 1415.. The synthesised beam of 30 arcsec x 30 arcsec is plotted at the left bottom corner of each sub-plot as a reference. The left image is the integrated HI column density map overlaid onto the DR8 DESI Legacy Imaging Survey g-band stacked images. The colour scale of blue, orange, red, purple, and olive green represent the contour levels of 1, 2, 5, 10, 20×10^20 cm−2, respectively. The middle image is the 1st moment velocity field map. The right plot is the spectra derived by the SOFIA software package, where the grey area represents the upper and lower limit of uncertainties. NGC 1415 is a large bright galaxy in which the HI traces various star-forming sites and is extended beyond the optical disk. The galaxy is seen mostly edge on, and the velocity map shows the lower side of the galaxy is rotating towards us and the upper side of the galaxy rotating away from us. A comparison of integrated HI flux densities revealed that ASKAP surprisingly detected more emission from NGC 1415 than Parkes single-dish observations, however, on further examination it was apparent that the HIPASS survey had only detected half of the galaxy.

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