Molecular content of the circumstellar disk in AB Aur: First detection of SO in a circumstellar disk

TL;DR

This study reports the first detection of SO molecules in a circumstellar disk around AB Aur, highlighting the disk's rich molecular content and providing insights into its young chemical state.

Contribution

It presents the first detection of SO in a circumstellar disk and compares molecular abundances across different disks, advancing understanding of disk chemistry.

Findings

Detected SO in AB Aur's disk, first such detection.

SO is less abundant in DM Tau compared to AB Aur.

Disk around AB Aur is chemically rich and young.

Abstract

Very few molecular species have been detected in circumstellar disks surrounding young stellar objects. We are carrying out an observational study of the chemistry of circumstellar disks surrounding T Tauri and Herbig Ae stars. First results of this study are presented in this note. We used the EMIR receivers recently installed at the IRAM 30m telescope to carry a sensitive search for molecular lines in the disks surrounding AB Aur, DM Tau, and LkCa 15. We detected lines of the molecules HCO+, CN, H2CO, SO, CS, and HCN toward AB Aur. In addition, we tentatively detected DCO+ and H2S lines. The line profiles suggest that the CN, HCN, H2CO, CS and SO lines arise in the disk. This makes it the first detection of SO in a circumstellar disk. We have unsuccessfully searched for SO toward DM Tau and LkCa 15, and for c-C3H2 toward AB Aur, DM Tau, and LkCa 15. Our upper limits show that contrary to all the molecular species observed so far, SO is not as abundant in DM Tau as it is in AB Aur. Our results demonstrate that the disk associated with AB Aur is rich in molecular species. Our chemical model shows that the detection of SO is consistent with that expected from a very young disk where the molecular adsorption onto grains does not yet dominate the chemistry.