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Non-Keplerian spirals, a gas-pressure dust trap, and an eccentric gas cavity in the circumbinary disc around HD 142527

Abstract : We present ALMA observations of the 12CO, 13CO, C18O J = 2-1 transitions and the 1.3 mm continuum emission for the circumbinary disc around HD 142527, at an angular resolution of ≍ 0${_{.}^{\prime\prime}}$3. We observe multiple spiral structures in intensity, velocity, and velocity dispersion for the 12CO and 13CO gas tracers. A newly detected 12CO spiral originates from the dust horseshoe, and is rotating at super-Keplerian velocity or vertically ascending, whilst the interspiral gas is rotating at sub-Keplerian velocities. This new spiral possibly connects to a previously identified spiral, thus spanning >360°. A spatial offset of 30 au is observed between the 12CO and 13CO spirals, to which we hypothesize that the gas layers are propagating at different speeds (surfing) due to a non-zero vertical temperature gradient. Leveraging the varying optical depths between the CO isotopologues, we reconstruct temperature and column density maps of the outer disc. Gas surface density peaks at r ≍ 180 au, coincident with the peak of continuum emission. Here, the dust grains have a Stokes number of ≍ 1, confirming radial and azimuthal trapping in the horseshoe. We measure a cavity radius at half-maximum surface density of ≍ 100 au, and a cavity eccentricity between 0.3 and 0.45.
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https://hal-insu.archives-ouvertes.fr/insu-03705304
Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Monday, June 27, 2022 - 8:54:45 AM
Last modification on : Tuesday, July 5, 2022 - 3:06:13 AM

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H. Garg, C. Pinte, V. Christiaens, D. J. Price, J. S. Lazendic, et al.. Non-Keplerian spirals, a gas-pressure dust trap, and an eccentric gas cavity in the circumbinary disc around HD 142527. Monthly Notices of the Royal Astronomical Society, 2021, 504, pp.782-791. ⟨10.1093/mnras/stab800⟩. ⟨insu-03705304⟩

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