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21st of January 2019
ASKAP images of the NGC 7232 galaxy group (Part 1)
by Karen Lee-Waddell
Lee-Waddell et al. (2019) have used the Australian Square Kilometre Array Pathfinder (ASKAP) to detect HI in the NGC 7232 galaxy group. The observations were taken on behalf of WALLABY (the Widefield ASKAP L-band Legacy All-sky Blind surveY) using 12 ASKAP antennas during various commissioning and Early Science phases of the array. The left panel shows circles representing the beams across ASKAP’s wide field of view, which are colour-coded based on each 36-beam footprint that can be simultaneously observed. Footprint A (red) is alternated with footprint B (blue) to provide more even sensitivity across the field. The rotated footprint (green) was observed during a couple of nights to test optimization based on the electronics of the Phased Array Feeds (PAFs). The right panel shows ASKAP total HI intensity contours (white) obtained from combining 150 hours of data from the central region of ASKAP beams. These high resolution ASKAP observations are able to spatially resolve several gas-rich galaxies. For comparison, single-dish HIPASS total intensity contours are shown in yellow. Within the region analyzed, ASKAP detects 17 HI sources. Eleven of these detections are identified with stellar counterparts, of which five are newly resolved HI galaxies (indicated by the blue diamonds). The other six HI detections (circled in green) are likely tidal debris associated with NGC 7232/3 triplet.

Reference: K. Lee-Waddell, B.S. Koribalski, T. Westmeier, A. Elagali, B.-Q. For, D. Kleiner, J.P. Madrid, A. Popping, T. N. Reynolds, J. Rhee, P. Serra, L. Shao, L. Staveley-Smith, J. Wang, M.T. Whiting, O.I. Wong, J.R. Allison, S. Bhandari, J.D. Collier, G. Heald, J. Marvil, S.M. Ord, 2019, MNRAS, in press (arXiv:1901.00241)

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