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11th of May 2021
Cavities in proto-planetary disks
by Norfolk et al.
Protoplanetary discs around young stars are the birth places of planets. Of particular interest are the so-called transition discs, which exhibit inner cavities in their dust distribution. One possible explanation is a dust trap; the trapping of dust at local maxima in the gas density. Dust grains interior to this region accrete onto the host star, depleting the inner disc and forming a cavity. Norfolk et al. have recently presented results from the Discs Down Under program, an 34 GHz continuum Australia Telescope Compact Array (ATCA) survey targeting 15 transition discs with large cavities, and compare the resulting dust emission to Atacama Large millimetre/sub-millimetre Array (ALMA) observations. The ATCA observations resolve the inner cavity for 8 of the 14 detected discs. They find that, for sources with a resolved cavity in both wavebands, the 8.8 mm and sub-mm brightness distributions peak at the same radius from the star, and suggest that a similar cavity size for 8.8 mm and sub-mm dust grains is due to a dust trap induced by the presence of a companion.

The images above are of one of the spatially resolved discs from the survey. The 2 arcsecond x 2 arcsecond images show the 34 GHz ATCA continuum image, 281 GHz ALMA continuum image, "degraded" ALMA continuum image (convolved with the ATCA beam), and the ALMA continuum maps overlaid with ATCA continuum contours. The similarity between the ATCA and ALMA images is evident.

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