Observational diagnostics of gas in protoplanetary disks

TL;DR

This review discusses various observational methods across multiple wavelengths to study the gas in protoplanetary disks, focusing on the inner 20 AU where planet formation occurs, highlighting current capabilities and future prospects.

Contribution

It provides a comprehensive overview of observational diagnostics for gas in protoplanetary disks, emphasizing their potential and limitations in probing planet-forming regions.

Findings

Multiple diagnostics across UV to sub-mm wavelengths are used to study disk gas.

Current methods have limitations in spatial resolution and sensitivity.

Future research prospects include improved instrumentation and techniques.

Abstract

Protoplanetary disks are composed primarily of gas (99% of the mass). Nevertheless, relatively few observational constraints exist for the gas in disks. In this review, I discuss several observational diagnostics in the UV, optical, near-IR, mid-IR, and (sub)-mm wavelengths that have been employed to study the gas in the disks of young stellar objects. I concentrate in diagnostics that probe the inner 20 AU of the disk, the region where planets are expected to form. I discuss the potential and limitations of each gas tracer and present prospects for future research.