期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 434, 期 4, 页码 3378-3388出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stt1254
关键词
protoplanetary discs; stars: pre-main-sequence
资金
- Canada Foundation for Innovation
- Cambridge University
- STFC
- STFC [ST/H004912/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/H004912/1] Funding Source: researchfish
We consider continuum free-free radio emission from the upper atmosphere of protoplanetary discs as a probe of the ionized luminosity impinging upon the disc. Making use of previously computed hydrodynamic models of disc photoevaporation within the framework of extreme-ultraviolet (EUV) and X-ray irradiation, we use radiative transfer post-processing techniques to predict the expected free-free emission from protoplanetary discs. In general, the free-free luminosity scales roughly linearly with ionizing luminosity in both EUV- and X-ray-driven scenarios, where the emission dominates over the dust tail of the disc and is partial optically thin at cm wavelengths. We perform a test observation of GM Aur at 14-18 GHz and detect an excess of radio emission above the dust tail to a very high level of confidence. The observed flux density and spectral index are consistent with free-free emission from the ionized disc in either the EUV- or the X-ray-driven scenario. Finally, we suggest a possible route to testing the EUV- and X-ray-driven dispersal model of protoplanetary discs, by combining observed free-free flux densities with measurements of mass-accretion rates. On the point of disc dispersal one would expect to find an (M)over dot(*)(2) scaling with free-free flux in the case of EUV-driven disc dispersal or an M-* scaling in the case of X-ray-driven disc dispersal.
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