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

Adam K. Leroy, Eva Schinnerer, Annie Hughes, Erik Rosolowsky, Jérôme Pety, Andreas Schruba, Antonio Usero, Guillermo A. Blanc, Mélanie Chevance, Eric Emsellem, Christopher M. Faesi, Cinthya N. Herrera, Daizhong Liu, Sharon E. Meidt, Miguel Querejeta, Toshiki Saito, Karin M. Sandstrom, Jiayi Sun, Thomas G. Williams, Gagandeep S. Anand, Ashley T. Barnes, Erica A. Behrens, Francesco Belfiore, Samantha M. Benincasa, Ivana Bešlić, Frank Bigiel, Alberto D. Bolatto, Jakob S. den Brok, Yixian Cao, Rupali Chandar, Jérémy Chastenet, I-Da Chiang, Enrico Congiu, Daniel A. Dale, Sinan Deger, Cosima Eibensteiner, Oleg V. Egorov, Axel García-Rodríguez, Simon C. O. Glover, Kathryn Grasha, Jonathan D. Henshaw, I-Ting Ho, Amanda A. Kepley, Jaeyeon Kim, Ralf S. Klessen, Kathryn Kreckel, Eric W. Koch, J. M. Diederik Kruijssen, Kirsten L. Larson, Janice C. Lee, Laura A. Lopez, Josh Machado, Ness Mayker, Rebecca McElroy, Eric J. Murphy, Eve C. Ostriker, Hsi-An Pan, Ismael Pessa, Johannes Puschnig, Alessandro Razza, Patricia Sánchez-Blázquez, Francesco Santoro, Amy Sardone, Fabian Scheuermann, Kazimierz Sliwa, Mattia C. Sormani, Sophia K. Stuber, David A. Thilker, Jordan A. Turner, Dyas Utomo, Elizabeth J. Watkins, Bradley Whitmore

Published 2021-04-15Version 1

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.