A major asymmetric ice trap in a planet-forming disk: II. prominent SO and SO2 pointing to C/O < 1

Abstract

Gas-phase sulphur bearing volatiles appear to be severely depleted in protoplanetary disks. The detection of CS and non-detections of SO and SO2 in many disks have shown that the gas in the warm molecular layer, where giant planets accrete their atmospheres, has a high C/O ratio. In this letter, we report the detection of SO and SO2 in the Oph-IRS 48 disk using ALMA. This is the first case of prominent SO2 emission detected from a protoplanetary disk. The molecular emissions of both molecules is spatially correlated with the asymmetric dust trap. We propose that this is due to the sublimation of ices at the edge of the dust cavity and that the bulk of the ice reservoir is coincident with the millimetre dust grains. Depending on the partition of elemental sulphur between refractory and volatile materials the observed molecules can account for 15-100% of the total sulphur budget in the disk. In strong contrast to previous results, we constrain the C/O ratio from the CS/SO ratio to be < 1 and potentially solar. This has important implications for the elemental composition of planets forming within the cavities of warm transition disks.

Accepted to A&A Letters 7th June 2021

References in corpus (14)

• Chemical enrichment of giant planets and discs due to pebble drift
• Meridional flows in the disk around a young star
• Herschel observations of EXtra-Ordinary Sources: Analysis of the HIFI 1.2 THz Wide Spectral Survey Toward Orion KL I. Methods
• On the diversity of asymmetries in gapped protoplanetary disks
• Sulfur chemistry in protoplanetary disks: CS and H2CS
• A new study of an old sink of sulfur in hot molecular cores: the sulfur residue
• Spatial separation of small and large grains in the transitional disk around the young star IRS 48
• A major asymmetric ice trap in a planet-forming disk: I. Formaldehyde and methanol
• Sulfur-driven Haze Formation in Warm CO2-rich Exoplanet Atmospheres
• ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT) V: Sample, overview, and demography of disk molecular emission
• AB Aur, a Rosetta stone for studies of planet formation (I): chemical study of a planet-forming disk
• Solving grain size inconsistency between ALMA polarization and VLA continuum in the Ophiuchus IRS 48 protoplanetary disk
• Spatially resolved HCN J=4--3 and CS J=7--6 emission from the disk around HD 142527
• ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT). IV. Thioformaldehyde (H${}_2$CS) in protoplanetary disks: spatial distributions and binding energies