Inner disc and circumplanetary material in the PDS 70 system

Abstract

The two giant protoplanets directly imaged in the dust-depleted cavity of PDS 70 offer a unique opportunity to study ongoing planet formation. Both planets have been detected in infrared thermal emission and in H$\hat{I}\pm$, indicating active accretion. We calibrate and analyse archival ALMA Band 6 and 7 observations of PDS 70 from 2019, 2021, and 2023 to search for circumplanetary material and assess its motion. Using 2D visibility modelling of the high-resolution (~0.11"x0.08" in Band 6; ~0.05"x0.05" in Band 7) dust continuum from the outer disc, we subtract the model and image the cavity at multiple epochs. We re-detect compact dust emission around PDS 70 c in all datasets with >$3.8\ddot{I}ƒ$ significance, and tentatively detect emission near PDS 70 b at ~$3\ddot{I}ƒ$ in Band 6, with peak fluxes of $59\pm 17\hat{I}¼$Jy/beam and $46\pm 14\hat{I}¼$Jy/beam. The relative astrometry of the compact emission around PDS 70 c is consistent with the expected position of the planet between 2019-2023. We find a peak flux difference up to $64\pm 34\hat{I}¼$Jy/beam at 1$\ddot{I}ƒ$, but Bayesian analysis indicates no significant variability. We detect no flux variability in the inner disc. The inferred dust mass near PDS 70 c and in the inner disc ranges from $0.008$-$0.063M_{\oplus }$ and $0.04$-$0.31M_{\oplus }$, respectively, consistent with prior estimates. Finally, we measure Band 6-7 spectral indices of $2.5\pm 1.2$ (PDS 70 c) and $3.2\pm 0.5$ (inner disc), suggesting that the inner disc emission is dominated by optically thin dust.

12 pages, 5 figures. Accepted for publication in A&A June 04, 2025