Dust Populations in the Iconic Vega Planetary System Resolved by ALMA

Left: Combined image of the Vega system at 1.34 mm using naturally weighted visibility data from both the ACA and 12m datasets, after applying a 1000 u-v taper to enhance the sensitivity to large-scale emission. Right: Same as left, but with imaging carried out after interferometrically removing the star from the visibilities, as described in §3.2. Contours are [2,4,6 ..]×70 µJy beam−1 , the RMS noise level of the images. No primary beam correction was applied to these images.

The Vega planetary system hosts the archetype of extrasolar Kuiper belts, and is rich in dust from the sub-au region out to 100's of au, suggesting intense dynamical activity.

We present ALMA mm observations that detect and resolve the outer dust belt from the star for the first time. The interferometric visibilities show that the belt can be fit by a Gaussian model or by power-law models with a steep inner edge (at 60-80 au). The belt is very broad, extending out to at least 150-200 au. We strongly detect the star and set a stringent upper limit to warm dust emission previously detected in the infrared. We discuss three scenarios that could explain the architecture of Vega's planetary system, including the new {ALMA} constraints: no outer planets, a chain of low-mass planets, and a single giant planet.

The planet-less scenario is only feasible if the outer belt was born with the observed sharp inner edge. If instead the inner edge is currently being truncated by a planet, then the planet must be ≳6 M⊕ and at ≲71 au to have cleared its chaotic zone within the system age. In the planet chain scenario, outward planet migration and inward scattering of planetesimals could produce the hot and warm dust observed in the inner regions of the system. In the single giant planet scenario, an asteroid belt could be responsible for the warm dust, and mean motion resonances with the planet could put asteroids on star-grazing orbits, producing the hot dust.

Luca Matrà, William R. F. Dent, David J. Wilner, Sebastián Marino, Mark C. Wyatt, Jonathan P. Marshall, Kate Y. L. Su, Miguel Chavez, Antonio Hales, A. Meredith Hughes, Jane S. Greaves, Stuartt A. Corder

Comments: 18 pages, 3 figures, Accepted for publication in ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2006.16257 [astro-ph.EP] (or arXiv:2006.16257v1 [astro-ph.EP] for this version)
Submission history
From: Luca Matrà
[v1] Mon, 29 Jun 2020 18:00:02 UTC (1,970 KB)

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