Investigating Sulfur Chemistry in the HD 163296 disk

TL;DR

This study combines ALMA observations and astrochemical modeling to analyze sulfur chemistry in the HD 163296 protoplanetary disk, revealing insights into molecule distributions and the influence of the C/O ratio.

Contribution

It provides the first detailed comparison of observed and modeled sulfur molecules in HD 163296, highlighting the role of the C/O ratio in sulfur chemistry.

Findings

Simulated CS column density matches observations.

C2S column density is lower than observational limits.

The N[CS]/N[SO] ratio indicates the disk's C/O ratio.

Abstract

Sulfur chemistry in the formation process of low-mass stars and planets remains poorly understood. The protoplanetary disks (PPDs) are the birthplace of planets and its distinctive environment provides an intriguing platform for investigating models of sulfur chemistry. We analyzed the ALMA observations of CS 7-6 transitions in the HD 163296 disk and perform astrochemical modeling to explore its sulfur chemistry. We simulated the distribution of sulfur-containing molecules and compared it with observationally deduced fractional column densities. We have found that the simulated column density of CS is consistent with the observationally deduced fractional column densities, while the simulated column density of C$_2$S is lower than the observationally deduced upper limits on column densities. This results indicate that we have a good understanding of the chemical properties of CS and C$_2$S in the disk. We also investigated the influence of the C/O ratio on sulfur-containing molecules and found that the column densities of SO, SO$_2$, and H$_2$S near the central star are dependent on the C/O ratio. Additionally, we found that the $N$[CS]/$N$[SO] ratio can serve as a promising indicator of the disk's C/O ratio in the HD 163296. Overall, the disk of HD 163296 provides a favorable environment for the detection of sulfur-containing molecules.