Abstract

We present ALMA observations of the (CO)-C-12, (CO)-C-13, (CO)-O-18 J = 2-1 transitions and the 1.3mm continuum emission for the circumbinary disc around HD 142527, at an angular resolution of approximate to 03. We observe multiple spiral structures in intensity, velocity, and velocity dispersion for the (CO)-C-12 and (CO)-C-13 gas tracers. A newly detected (CO)-C-12 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 degrees. A spatial offset of 30au is observed between the (CO)-C-12 and (CO)-C-13 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 approximate to 180au, coincident with the peak of continuum emission. Here, the dust grains have a Stokes number of approximate to 1, confirming radial and azimuthal trapping in the horseshoe. We measure a cavity radius at half-maximum surface density of approximate to 100au, and a cavity eccentricity between 0.3 and 0.45.