ALMA-IMF. I. Investigating the origin of stellar masses: Introduction to the Large Program and first results

Frédérique Motte (1) , Sylvain Bontemps (2) , Timéa Csengeri (2) , Yohan Pouteau (1) , Fabien Louvet (1, 3, 4) , Amelia M. Stutz (5, 6) , Nichol Cunningham (1) , Ana López-Sepulcre (1) , Nathalie Brouillet (2) , Roberto Galván-Madrid (7) , Adam Ginsburg (8) , Luke Maud (9) , Alexander Men’shchikov (3) , Fumitaka Nakamura (10, 11) , Thomas Nony (7) , Patricio Sanhueza (10, 11) , Rodrigo H. Álvarez-Gutiérrez (5) , Mélanie Armante (12, 13) , Tapas Baug (14) , Melisse Bonfand (15) , Gemma Busquet (1, 16, 17) , Edwige Chapillon (15, 18) , Daniel Díaz-González (7) , Manuel Fernández-López (19) , Andrés Guzmán (10) , Fabrice Herpin (15) , Hong-Li Liu (5, 20) , Fernando A. Olguin (21) , Allison P. M. Towner (8) , John Bally (22) , Cara Battersby (23) , Jonathan Braine (15) , Leonardo Bronfman (4) , H.-R. V. Chen (21) , Pierre Dell'Ova (12) , James Di Francesco (24) , Marta González (1) , Antoine Gusdorf (12) , Patrick Hennebelle (3) , Natsuko Izumi (10, 25, 26) , Isabelle Joncour (1) , Yueh-Ning Lee (27) , Bertrand Lefloch (1) , Pierre Lesaffre (12) , Xing Lu (3) , Karl Menten (28) , Raphaël Mignon-Risse (3) , Jordan Molet (15) , Estelle Moraux (1) , Lee Mundy (29) , Quang Nguyen Luong (30) , Nastassia Reyes (31) , Nicolas Reyes (28, 4) , S. D. Reyes Reyes (5) , Jean-François Robitaille (1) , Erik Rosolowsky (32) , Nicolas Antonio Sandoval-Garrido (5) , Frédéric Schuller (28, 33) , Brian E Svoboda (34) , Ken'Ichi Tatematsu (10) , Benjamin Thomasson (1) , Daniel Lewis Walker (23) , Benjamin Wu (10, 35) , Anthony Whitworth (36) , Friedrich Wyrowski (28)

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
2 FEMIS 2021
3 AIM (UMR_7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
4 UCHILE - Universidad de Chile = University of Chile [Santiago]
5 Universidad de Concepción - University of Concepcion [Chile]
6 MPIA - Max Planck Institute for Astronomy
7 IRyA - Instituto de Radioastronomía y Astrofísica [Mexico]
8 UF - University of Florida [Gainesville]
9 ESO - European Southern Observatory
10 NAOJ - National Astronomical Observatory of Japan
11 SOKENDAI - Graduate University for Advanced Studies [Hayama]
12 Astrophysique
13 Observatoire de Paris
14 S. N. Bose National Centre for Basic Sciences
15 LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac]
16 ICE-CSIC - Institut de Ciencies de l'Espai [Barcelona]
17 IEEC-CSIC - Institut d'Estudis Espacials de Catalunya
18 IRAM - Institut de RadioAstronomie Millimétrique
19 IAR - Instituto Argentino de Radioastronomia
20 Yunnan University
21 NTHU - National Tsing Hua University [Hsinchu]
22 Department of Astrophysical and Planetary Sciences [Boulder]
23 UCONN - University of Connecticut
24 NRC - National Research Council of Canada
25 Ibaraki University
26 ASIAA - Academia Sinica Institute of Astronomy and Astrophysics
27 NTNU - National Taiwan Normal University
28 Max Planck Institute for Radio Astronomy
29 University of Maryland [College Park]
30 AUP - The American University of Paris
31 UMR MARBEC - MARine Biodiversity Exploitation and Conservation - MARBEC
32 University of Alberta
33 AIP - Leibniz-Institut für Astrophysik Potsdam
34 NRAO - National Radio Astronomy Observatory [Socorro]
35 NVIDIA Research [Austin]
36 School of Physics and Astronomy [Cardiff]

Aims. Thanks to the high angular resolution, sensitivity, image fidelity, and frequency coverage of ALMA, we aim to improve our understanding of star formation. One of the breakthroughs expected from ALMA, which is the basis of our Cycle 5 ALMA-IMF Large Program, is the question of the origin of the initial mass function (IMF) of stars. Here we present the ALMA-IMF protocluster selection, first results, and scientific prospects.Methods. ALMA-IMF imaged a total noncontiguous area of ~53 pc2, covering extreme, nearby protoclusters of the Milky Way. We observed 15 massive (2.5 −33 × 103 M⊙), nearby (2−5.5 kpc) protoclusters that were selected to span relevant early protocluster evolutionary stages. Our 1.3 and 3 mm observations provide continuum images that are homogeneously sensitive to point-like cores with masses of ~0.2 M⊙ and ~0.6 M⊙, respectively, with a matched spatial resolution of ~2000 au across the sample at both wavelengths. Moreover, with the broad spectral coverage provided by ALMA, we detect lines that probe the ionized and molecular gas, as well as complex molecules. Taken together, these data probe the protocluster structure, kinematics, chemistry, and feedback over scales from clouds to filaments to cores.Results. We classify ALMA-IMF protoclusters as Young (six protoclusters), Intermediate (five protoclusters), or Evolved (four proto-clusters) based on the amount of dense gas in the cloud that has potentially been impacted by H II region(s). The ALMA-IMF catalog contains ~700 cores that span a mass range of ~0.15 M⊙ to ~250 M⊙ at a typical size of ~2100 au. We show that this core sample has no significant distance bias and can be used to build core mass functions (CMFs) at similar physical scales. Significant gas motions, which we highlight here in the G353.41 region, are traced down to core scales and can be used to look for inflowing gas streamers and to quantify the impact of the possible associated core mass growth on the shape of the CMF with time. Our first analysis does not reveal any significant evolution of the matter concentration from clouds to cores (i.e., from 1 pc to 0.01 pc scales) or from the youngest to more evolved protoclusters, indicating that cloud dynamical evolution and stellar feedback have for the moment only had a slight effect on the structure of high-density gas in our sample. Furthermore, the first-look analysis of the line richness toward bright cores indicates that the survey encompasses several tens of hot cores, of which we highlight the most massive in the G351.77 cloud. Their homogeneous characterization can be used to constrain the emerging molecular complexity in protostars of high to intermediate masses.Conclusions. The ALMA-IMF Large Program is uniquely designed to transform our understanding of the IMF origin, taking the effects of cloud characteristics and evolution into account. It will provide the community with an unprecedented database with a high legacy value for protocluster clouds, filaments, cores, hot cores, outflows, inflows, and stellar clusters studies.

Mots clés: stars: formation; stars: luminosity function; mass function; stars: protostars; ISM: clouds; evolution; H II regions

Domaines: Astrophysique [astro-ph]

Frédérique Motte, Sylvain Bontemps, Timéa Csengeri, Yohan Pouteau, Fabien Louvet, et al.. ALMA-IMF. I. Investigating the origin of stellar masses: Introduction to the Large Program and first results. Astronomy and Astrophysics - A&A, 2022, 662, pp.A8. ⟨10.1051/0004-6361/202141677⟩. ⟨hal-03683790⟩