An unbiased ALMA spectral survey of the LkCa 15 and MWC 480 protoplanetary disks

TL;DR

This paper presents an unbiased ALMA spectral survey of two protoplanetary disks, detecting 14 molecules and revealing significant differences in their chemical compositions, thus enhancing understanding of disk chemistry and physical conditions.

Contribution

It provides the first comprehensive, sensitive spectral line survey of these disks, detecting new molecules and comparing their chemical inventories in detail.

Findings

Detected 14 molecular species, including 5 new in disks.

Observed significant differences in molecular inventories between the two disks.

Survey increased sensitivity by an order of magnitude over previous studies.

Abstract

The volatile contents of protoplanetary disks both set the potential for planetary chemistry and provide valuable probes of defining disk system characteristics such as stellar mass, gas mass, ionization, and temperature structure. Current disk molecular inventories are fragmented, however, giving an incomplete picture: unbiased spectral line surveys are needed to assess the volatile content. We present here an overview of such a survey of the protoplanetary disks around the Herbig Ae star MWC 480 and the T Tauri star LkCa 15 in ALMA Band 7, spanning $\sim$36 GHz from 275--317 GHz and representing an order of magnitude increase in sensitivity over previous single-dish surveys. We detect 14 molecular species (including isotopologues), with 5 species (C$^{34}$S, $^{13}$CS, H$_{2}$CS, DNC, and C$_2$D) detected for the first time in protoplanetary disks. Significant differences are observed in the molecular inventories of MWC~480 and LkCa~15, and we discuss how these results may be interpreted in light of the different physical conditions of these two disk systems.