Herschel-HOBYS study of the earliest phases of high-mass star formation in NGC 6357★★★

D. Russeil (1) , M. Figueira (1) , Annie Zavagno (1) , F. Motte (2) , N. Schneider (3, 4) , A. Men’shchikov (5) , Sylvain Bontemps (6) , P. André (5) , L. D. Anderson (7) , M. Benedettini (8) , P. Didelon (5) , J. Di Francesco (8) , D. Elia (8) , V. Könyves (5, 9) , Q. Nguyen Luong (10, 11) , T. Nony (2) , S. Pezzuto (8) , K. L. J. Rygl (12) , E. Schisano (8) , L. Spinoglio (8) , J. Tigé (1) , G. J. White (13)

1 LAM - Laboratoire d'Astrophysique de Marseille
2 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
3 University of Cologne
4 LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac]
5 AIM (UMR7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
6 FORMATION STELLAIRE 2019
7 CGWA - Center for Gravitational Wave Astronomy
8 IAPS - Istituto di Astrofisica e Planetologia Spaziali - INAF
9 Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy [Preston]
10 KASI - Korea Astronomy and Space Science Institute
11 NAOJ Chile Observatory
12 OABO - INAF - Osservatorio Astronomico di Bologna
13 RAL Space - Space Science and Technology Department [Didcot]

Aims. To constrain models of high-mass star formation it is important to identify the massive dense cores (MDCs) that are able to form high-mass star(s). This is one of the purposes of the Herschel/HOBYS key programme. Here, we carry out the census and characterise of the properties of the MDCs population of the NGC 6357 H II region.Methods. Our study is based on the Herschel/PACS and SPIRE 70−500 μm images of NGC 6357 complemented with (sub-)millimetre and mid-infrared data. We followed the procedure established by the Herschel/HOBYS consortium to extract ~0.1 pc massive dense cores using the getsources software. We estimated their physical parameters (temperatures, masses, luminosities) from spectral energy distribution (SED) fitting.Results. We obtain a complete census of 23 massive dense cores, amongst which one is found to be IR-quiet and twelve are starless, representing very early stages of the star-formation process. Focussing on the starless MDCs, we have considered their evolutionary status, and suggest that only five of them are likely to form a high-mass star.Conclusions. We find that, contrarily to the case in NGC 6334, the NGC 6357 region does not exhibit any ridge or hub features that are believed to be crucial to the massive star formation process. This study adds support for an empirical model in which massive dense cores and protostars simultaneously accrete mass from the surrounding filaments. In addition, the massive star formation in NGC 6357 seems to have stopped and the hottest stars in Pismis 24 have disrupted the filaments.

Mots clés: stars: formation; stars: massive

Domaines: Astrophysique [astro-ph]; Astrophysique galactique [astro-ph.GA]

D. Russeil, M. Figueira, Annie Zavagno, F. Motte, N. Schneider, et al.. Herschel-HOBYS study of the earliest phases of high-mass star formation in NGC 6357★★★. Astronomy and Astrophysics - A&A, 2019, 625, pp.A134. ⟨10.1051/0004-6361/201833870⟩. ⟨cea-02143113⟩