Molecules with ALMA at Planet-forming Scales (MAPS) I: Program Overview and Highlights

TL;DR

The MAPS ALMA program investigates the chemical structures of five planet-forming disks at high resolution, revealing links between dust, gas, and chemistry that reshape our understanding of planet formation processes.

Contribution

This study provides the first comprehensive high-resolution chemical mapping of multiple disks, uncovering new insights into disk chemistry and planet formation environments.

Findings

Discovered links between dust, gas, and chemical sub-structures.

Found large reservoirs of nitriles and organics in inner disk regions.

Observed elevated C/O ratios across most disks.

Abstract

Planets form and obtain their compositions in dust and gas-rich disks around young stars, and the outcome of this process is intimately linked to the disk chemical properties. The distributions of molecules across disks regulate the elemental compositions of planets, including C/N/O/S ratios and metallicity (O/H and C/H), as well as access to water and prebiotically relevant organics. Emission from molecules also encodes information on disk ionization levels, temperature structures, kinematics, and gas surface densities, which are all key ingredients of disk evolution and planet formation models. The Molecules with ALMA at Planet-forming Scales (MAPS) ALMA Large Program was designed to expand our understanding of the chemistry of planet formation by exploring disk chemical structures down to 10 au scales. The MAPS program focuses on five disks - around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480 - in which dust substructures are detected and planet formation appears to be ongoing. We observed these disks in 4 spectral setups, which together cover ~50 lines from over 20 different species. This paper introduces the ApJS MAPS Special Issue by presenting an overview of the program motivation, disk sample, observational details, and calibration strategy. We also highlight key results, including discoveries of links between dust, gas, and chemical sub-structures, large reservoirs of nitriles and other organics in the inner disk regions, and elevated C/O ratios across most disks. We discuss how this collection of results is reshaping our view of the chemistry of planet formation.