ALMA-IMF

II. Investigating the origin of stellar masses: Continuum images and data processing^⋆

¹ Department of Astronomy, University of Florida, PO Box 112055 Florida, USA
e-mail: adam.g.ginsburg@gmail.com
² Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
³ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia, Michoacán 58089, Mexico
⁴ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁵ Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, 4030000 Concepción, Chile
⁶ S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
⁷ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁸ Institut de Ciències de l’Espai (ICE, CSIC), Can Magrans, s/n, 08193 Cerdanyola del Vallès, Catalonia, Spain
⁹ Institut d’Estudis Espacials de Catalunya (IEEC), 08340 Barcelona, Catalonia, Spain
¹⁰ Instituto Argentino de Radioastronomía (CCT-La Plata, CONICET; CICPBA), C.C. No. 5, 1894, Villa Elisa, Buenos Aires, Argentina
¹¹ National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹² Department of Astronomy, Yunnan University, Kunming 650091, PR China
¹³ Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint-Martin-D’Hères, France
¹⁴ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
¹⁵ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
¹⁶ LERMA (UMR CNRS 8112), École Normale Supérieure, 75231 Paris Cedex, France
¹⁷ ESO Headquarters, Karl-Schwarzchild-Str 2, 85748 Garching, Germany
¹⁸ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁹ Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
²⁰ The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
²¹ Institute of Astronomy, National Tsing Hua University, Hsinchu 30013, Taiwan
²² Department of Astronomical Science, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
²³ Max-Planck-Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
²⁴ Laboratoire de Physique de l’Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 75005 Paris, France
²⁵ University of Connecticut, Department of Physics, 196A Auditorium Road, Unit 3046, Storrs, CT 06269, USA
²⁶ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
²⁷ Herzberg Astronomy and Astrophysics Research Centre, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
²⁸ College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan
²⁹ Institute of Astronomy and Astrophysics, Academia Sinica, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
³⁰ AIM, IRFU, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
³¹ Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany
³² Department of Astronomy, University of Maryland, College Park, MD 20742, USA
³³ 4-183 CCIS, University of Alberta, Edmonton, Alberta, Canada
³⁴ Jansky fellow of the National Radio Astronomy Observatory, Socorro, NM 87801, USA
³⁵ School of Physics and Astronomy, Cardiff University, Cardiff, UK
³⁶ NVIDIA Research, 2788 San Tomas Expy, Santa Clara, CA 95051, USA
³⁷ Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago de Chile, Chile

Received: 25 June 2021
Accepted: 21 September 2021

Abstract

We present the first data release of the ALMA-IMF Large Program, which covers the 12m-array continuum calibration and imaging. The ALMA-IMF Large Program is a survey of fifteen dense molecular cloud regions spanning a range of evolutionary stages that aims to measure the core mass function. We describe the data acquisition and calibration done by the Atacama Large Millimeter/submillimeter Array (ALMA) observatory and the subsequent calibration and imaging we performed. The image products are combinations of multiple 12 m array configurations created from a selection of the observed bandwidth using multi-term, multi-frequency synthesis imaging and deconvolution. The data products are self-calibrated and exhibit substantial noise improvements over the images produced from the delivered data. We compare different choices of continuum selection, calibration parameters, and image weighting parameters, demonstrating the utility and necessity of our additional processing work. Two variants of continuum selection are used and will be distributed: the “best-sensitivity” (bsens) data, which include the full bandwidth, including bright emission lines that contaminate the continuum, and “cleanest” (cleanest), which select portions of the spectrum that are unaffected by line emission. We present a preliminary analysis of the spectral indices of the continuum data, showing that the ALMA products are able to clearly distinguish free-free emission from dust emission, and that in some cases we are able to identify optically thick emission sources. The data products are made public with this release.