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

• Published in: arXiv.org 2021-03
• Main Authors: Garg, Himanshi, Pinte, Christophe, Christiaens, Valentin, Price, Daniel, Lazendic, Jasmina, Boehler, Yann, Casassus, Simon, Marino, Sebastian, Perez, Sebastian, Zuleta, Andres
• Format: Article
• Language: English
• Subjects: Angular resolution; Carbon monoxide; Continuum radiation; Density; Dust; Emission; Rotation; Spirals; Stokes number; Surfing; Temperature gradients; Tracers
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2010.15310

We present ALMA observations of the \(^{12}\)CO, \(^{13}\)CO, C\(^{18}\)O J=2-1 transitions and the 1.3\,mm continuum emission for the circumbinary disc around HD 142527, at an angular resolution of \(\approx\)\,0\farcs3. We observe multiple spiral structures in intensity, velocity and velocity dispersion for the \(^{12}\)CO and \(^{13}\)CO gas tracers. A newly detected \(^{12}\)CO spiral originates from the dust horseshoe, and is rotating at super-Keplerian velocity or vertically ascending, whilst the inter-spiral gas is rotating at sub-Keplerian velocities. This new spiral possibly connects to a previously identified spiral, thus spanning > 360\(^\circ\). A spatial offset of ~30 au is observed between the \(^{12}\)CO and \(^{13}\)CO 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\,\(\approx\)\,180\,au, coincident with the peak of continuum emission. Here the dust grains have a Stokes number of \(\approx\)\,1, confirming radial and azimuthal trapping in the horseshoe. We measure a cavity radius at half-maximum surface density of \(\approx\)\,100\,au, and a cavity eccentricity between 0.3 and 0.45.