A sensitive, high-resolution, wide-field IRAM NOEMA CO(1–0) survey of the very nearby spiral galaxy IC 342^⋆

¹ Observatorio Astronómico Nacional (IGN), C/Alfonso XII, 3, 28014 Madrid, Spain
e-mail: m.querejeta@oan.es
² Institut de Radioastronomie Millimétrique (IRAM), 300 Rue de la Piscine, 38406 Saint-Martin-d’Hères, France
³ Sorbonne Université, Observatoire de Paris, Université PSL, CNRS, LERMA, 75014 Paris, France
⁴ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching, Germany
⁵ Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
⁶ Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble, France
⁷ Institute of Astronomy and Astrophysics, Academia Sinica, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan
⁸ Center for Astrophysics and Space Sciences, Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
⁹ Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium
¹⁰ Department of Physics, University of Alberta, Edmonton, AB T6G 2E1, Canada
¹¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹² Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1, Canada
¹³ Canadian Institute for Theoretical Astrophysics (CITA), University of Toronto, 60 St George St, Toronto, ON M5S 3H8, Canada
¹⁴ Penn State Mont Alto, 1 Campus Drive, Mont Alto, PA 17237, USA
¹⁵ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹⁶ Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str 2, 69120 Heidelberg, Germany
¹⁷ Cosmic Origins Of Life (COOL) Research DAO, coolresearch.io
¹⁸ European Southern Observatory, Karl-Schwarzschild Straße 2, 85748 Garching bei München, Germany
¹⁹ Univ Lyon, Univ Lyon 1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, 69230 Saint-Genis-Laval, France
²⁰ Department of Physics, University of Connecticut, Storrs, CT 06269, USA
²¹ CNRS, IRAP, 9 Av. du Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
²² Université de Toulouse, UPS-OMP, IRAP, 31028 Toulouse Cedex 4, France
²³ Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Im Neuenheimer Feld 205, 69120 Heidelberg, Germany
²⁴ Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, 69120 Heidelberg, Germany
²⁵ Technical University of Munich, School of Engineering and Design, Department of Aerospace and Geodesy, Chair of Remote Sensing Technology, Arcisstr. 21, 80333 Munich, Germany
²⁶ Department of Physics, Tamkang University, No. 151, Yingzhuan Rd., Tamsui Dist., New Taipei City 251301, Taiwan
²⁷ Department of Astronomy & Astrophysics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA

Received: 31 December 2021
Accepted: 3 October 2023

Abstract

We present a new wide-field 10.75 × 10.75 arcmin² (≈11 × 11 kpc²), high-resolution (θ = 3.6″ ≈ 60 pc) NOEMA CO(1–0) survey of the very nearby (d = 3.45 Mpc) spiral galaxy IC 342. The survey spans out to about 1.5 effective radii and covers most of the region where molecular gas dominates the cold interstellar medium. We resolved the CO emission into > 600 individual giant molecular clouds and associations. We assessed their properties and found that overall the clouds show approximate virial balance, with typical virial parameters of α_vir = 1 − 2. The typical surface density and line width of molecular gas increase from the inter-arm region to the arm and bar region, and they reach their highest values in the inner kiloparsec of the galaxy (median Σ_mol ≈ 80, 140, 160, and 1100 M_⊙ pc⁻², σ_CO ≈ 6.6, 7.6, 9.7, and 18.4 km s⁻¹ for inter-arm, arm, bar, and center clouds, respectively). Clouds in the central part of the galaxy show an enhanced line width relative to their surface densities and evidence of additional sources of dynamical broadening. All of these results agree well with studies of clouds in more distant galaxies at a similar physical resolution. Leveraging our measurements to estimate the density and gravitational free-fall time at 90 pc resolution, averaged on 1.5 kpc hexagonal apertures, we estimate a typical star formation efficiency per free-fall time of 0.45% with a 16 − 84% variation of 0.33 − 0.71% among such 1.5 kpc regions. We speculate that bar-driven gas inflow could explain the large gas concentration in the central kiloparsec and the buildup of the massive nuclear star cluster. This wide-area CO map of the closest face-on massive spiral galaxy demonstrates the current mapping power of NOEMA and has many potential applications. The data and products are publicly available.