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16th of June 2015
ASKAP HI imaging of the galaxy group IC 1459
by Paolo Serra (CASS)
During the last year, the ASKAP commissioning team has produced many images of the radio sky using the first 6 ASKAP antennas equipped with phased array feeds. One of these observations was aimed at studying the distribution of neutral hydrogen (HI) gas in the galaxy group IC 1459. It resulted in the resolved HI imaging of 11 galaxies in the group (see image on the left, showing HI contours in red overlaid on an optical image) and in the discovery of 3 previously unknown HI clouds, each containing ~1 billion solar masses of gas (see cut-out images on the right). The data show that the clouds are, in fact, the tip of the iceberg of a diffuse distribution of HI in the group medium. HI found outside galaxies in this group amounts to at least 10% of the HI contained inside galaxies. This suggests a substantial flow of gas in and out of galaxies during the several billion years of the group's evolution. This work is presented in a paper (Serra, Koribalski, Kilborn et al. 2015), now accepted for publication on MNRAS and available at astro-ph/1506.04399.

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