Dynamics of cluster-forming hub-filament systems: The case of the high-mass star-forming complex Monoceros R2

S P Treviño-Morales; A Fuente; Á Sánchez-Monge; J Kainulainen; P Didelon; S Suri; N Schneider; J Ballesteros-Paredes; Y-N Lee; P Hennebelle; P Pilleri; M González-García; C Kramer; S García-Burillo; A Luna; J R Goicoechea; P Tremblin; S Geen

doi:10.1051/0004-6361/201935260

Dynamics of cluster-forming hub-filament systems: The case of the high-mass star-forming complex Monoceros R2

Astron Astrophys. 2019 Sep:629:A81. doi: 10.1051/0004-6361/201935260. Epub 2019 Sep 12.

Authors

S P Treviño-Morales¹, A Fuente², Á Sánchez-Monge³, J Kainulainen^{1

4}, P Didelon⁵, S Suri^{3

4}, N Schneider³, J Ballesteros-Paredes⁶, Y-N Lee⁷, P Hennebelle⁵, P Pilleri⁸, M González-García⁹, C Kramer¹⁰, S García-Burillo², A Luna¹¹, J R Goicoechea¹², P Tremblin⁵, S Geen¹³

Affiliations

¹ Chalmers University of Technology, Department of Space, Earth and Environment, SE-412 93 Gothenburg, Sweden.
² Observatorio Astronómico Nacional, Apdo. 112, 28803 Alcalá de Henares Madrid, Spain.
³ I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany.
⁴ Max-Planck-Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany.
⁵ Laboratoire AIM, Paris-Saclay, CEA/IRFU/SAp - CNRS - Université Paris Diderot, 91191 Gif-sur-Yvette Cedex, France.
⁶ Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, P.O. Box 3-72, 58090 Morelia, Mexico.
⁷ Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, UMR 7154 CNRS, 75005 Paris, France.
⁸ IRAP, Université de Toulouse, CNRS, UPS, CNES, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France.
⁹ Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain.
¹⁰ Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint Martin d'Hères, France.
¹¹ Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis Enrique Erro #1, 72840 Tonantzintla, Puebla, Mexico.
¹² Instituto de Física Fundamental (CSIC). Calle Serrano 121, E-28006, Madrid, Spain.
¹³ Zentrum für Astronomie, Institut für Theoretische Astrophysik, Universität Heidelberg, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany.

Abstract

Context: High-mass stars and star clusters commonly form within hub-filament systems. Monoceros R2 (hereafter Mon R2), at a distance of 830 pc, harbors one of the closest such systems, making it an excellent target for case studies.

Aims: We investigate the morphology, stability and dynamical properties of the Mon R2 hub-filament system.

Methods: We employ observations of the ¹³CO and C¹⁸O 1→0 and 2→1 lines obtained with the IRAM-30m telescope. We also use H₂ column density maps derived from Herschel dust emission observations.

Results: We identified the filamentary network in Mon R2 with the DisPerSE algorithm and characterized the individual filaments as either main (converging into the hub) or secondary (converging to a main filament) filaments. The main filaments have line masses of 30-100 M _⊙ pc^-1 and show signs of fragmentation, while the secondary filaments have line masses of 12-60 M _⊙ pc^-1 and show fragmentation only sporadically. In the context of Ostriker's hydrostatic filament model, the main filaments are thermally supercritical. If non-thermal motions are included, most of them are trans-critical. Most of the secondary filaments are roughly transcritical regardless of whether non-thermal motions are included or not. From the morphology and kinematics of the main filaments, we estimate a mass accretion rate of 10^-4-10^-3 M _⊙ yr^-1 into the central hub. The secondary filaments accrete into the main filaments with a rate of 0.1-0.4×10^-4 M _⊙ yr^-1. The main filaments extend into the central hub. Their velocity gradients increase towards the hub, suggesting acceleration of the gas.We estimate that with the observed infall velocity, the mass-doubling time of the hub is ~ 2:5 Myr, ten times larger than the free-fall time, suggesting a dynamically old region. These timescales are comparable with the chemical age of the Hii region. Inside the hub, the main filaments show a ring- or a spiral-like morphology that exhibits rotation and infall motions. One possible explanation for the morphology is that gas is falling into the central cluster following a spiral-like pattern.

Keywords: ISM: clouds; ISM: hub-filament systems; ISM: kinematics and dynamics; ISM: structure; Individual: Monoceros R2; Stars: massive formation.

Grants and funding

610256/ERC_/European Research Council/International