PHANGS-ALMA: Arcsecond CO(2-1) Imaging of Nearby Star-Forming Galaxies

TL;DR

PHANGS-ALMA is a pioneering survey that maps CO(2-1) emission at ~100pc resolution across 90 nearby star-forming galaxies, enabling detailed study of molecular clouds and star formation in the local universe.

Contribution

This work provides the first high-resolution CO(2-1) imaging survey of a representative sample of nearby galaxies, with comprehensive data products and analysis tools.

Findings

First 1" resolution atlas of CO emission in nearby galaxies

Detailed measurements of molecular gas properties and demographics

Public data release enabling further research

Abstract

We present PHANGS-ALMA, the first survey to map CO J=2-1 line emission at ~1" ~ 100pc spatial resolution from a representative sample of 90 nearby (d<~20 Mpc) galaxies that lie on or near the z=0 "main sequence" of star-forming galaxies. CO line emission traces the bulk distribution of molecular gas, which is the cold, star-forming phase of the interstellar medium. At the resolution achieved by PHANGS-ALMA, each beam reaches the size of a typical individual giant molecular cloud (GMC), so that these data can be used to measure the demographics, life-cycle, and physical state of molecular clouds across the population of galaxies where the majority of stars form at z=0. This paper describes the scientific motivation and background for the survey, sample selection, global properties of the targets, ALMA observations, and characteristics of the delivered ALMA data and derived data products. As the ALMA sample serves as the parent sample for parallel surveys with VLT/MUSE, HST, AstroSat, VLA, and other facilities, we include a detailed discussion of the sample selection. We detail the estimation of galaxy mass, size, star formation rate, CO luminosity, and other properties, compare estimates using different systems and provide best-estimate integrated measurements for each target. We also report the design and execution of the ALMA observations, which combine a Cycle~5 Large Program, a series of smaller programs, and archival observations. Finally, we present the first 1" resolution atlas of CO emission from nearby galaxies and describe the properties and contents of the first PHANGS-ALMA public data release.