Multi-scale analysis of the Monoceros OB 1 star-forming region

II. Colliding filaments in the Monoceros OB1 molecular cloud^★

¹ Institut UTINAM – UMR 6213 – CNRS – University of Bourgogne Franche Comté, France, OSU THETA, 41bis avenue de l’Observatoire, 25000 Besançon, France
e-mail: julien@obs-besancon.fr
² Department of Physics, University of Helsinki, PO Box 64, 00014, Finland
³ IRAP, Université de Toulouse, CNRS, UPS, CNES, 31400 Toulouse, France
⁴ Yunnan Observatories, Chinese Academy of Sciences, 396 Yangfangwang, Guandu, Kunming, 650216, PR China
⁵ Chinese Academy of Sciences, South America Center for Astrophysics (CASSACA), Camino El Observatorio 1515, Las Condes, Santiago, Chile
⁶ Departamento de Astronomía, Universidad de Chile, Las Condes, Santiago, Chile
⁷ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, PR China
⁸ Korea Astronomy and Space Science Institute, 776 Daedeokdaero, Yuseong-gu, Daejeon 34055, Republic of Korea
⁹ East Asian Observatory, 660 N. A’ohoku Place, Hilo, HI 96720, USA
¹⁰ Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK
¹¹ University of Science & Technology, 176 Gajeong-dong, Yuseong-gu, Daejeon, Republic of Korea
¹² Academia Sinica, Institute of Astronomy and Astrophysics, Taipei, Taiwan
¹³ National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁴ SOFIA Science Centre, USRA, NASA Ames Research Centre, MS N232-12 Moffett Field, CA 94035, USA
¹⁵ Department of Physical Science, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
¹⁶ Department of Physics, School of Science and Humanities, Kabanbay batyr ave, 53, Nur-Sultan 010000, Kazakhstan
¹⁷ Eötvös Loránd University, Department of Astronomy, Pázmány Péter sétány 1/A, 1117, Budapest, Hungary
¹⁸ Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
¹⁹ Institute of Physics I, University of Cologne, Zülpicher Str. 77, 50937, Cologne, Germany
²⁰ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
²¹ ICC, University of Barcelona, Marti i Franquès 1, 08028 Barcelona, Spain
²² Konkoly Observatory of the Hungarian Academy of Sciences, 1121 Budapest, Konkoly Thege Miklósút 15-17, Hungary
²³ IAPS – INAF, via Fosso del Cavaliere 100, 00133, Rome, Italy
²⁴ Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, PR China
²⁵ European Southern Observatory (ESO) Headquarters, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany

Received: 17 December 2018
Accepted: 26 August 2019

Abstract

Context. We started a multi-scale analysis of star formation in G202.3+2.5, an intertwined filamentary sub-region of the Monoceros OB1 molecular complex, in order to provide observational constraints on current theories and models that attempt to explain star formation globally. In the first paper (Paper I), we examined the distributions of dense cores and protostars and found enhanced star formation activity in the junction region of the filaments.

Aims. In this second paper, we aim to unveil the connections between the core and filament evolutions, and between the filament dynamics and the global evolution of the cloud.

Methods. We characterise the gas dynamics and energy balance in different parts of G202.3+2.5 using infrared observations from the Herschel and WISE telescopes and molecular tracers observed with the IRAM 30-m and TRAO 14-m telescopes. The velocity field of the cloud is examined and velocity-coherent structures are identified, characterised, and put in perspective with the cloud environment.

Results. Two main velocity components are revealed, well separated in radial velocities in the north and merged around the location of intense N₂H⁺ emission in the centre of G202.3+2.5 where Paper I found the peak of star formation activity. We show that the relative position of the two components along the sightline, and the velocity gradient of the N₂H⁺ emission imply that the components have been undergoing collision for ~10⁵ yr, although it remains unclear whether the gas moves mainly along or across the filament axes. The dense gas where N₂H⁺ is detected is interpreted as the compressed region between the two filaments, which corresponds to a high mass inflow rate of ~1 × 10⁻³ M_⊙ yr⁻¹ and possibly leads to a significant increase in its star formation efficiency. We identify a protostellar source in the junction region that possibly powers two crossed intermittent outflows. We show that the H II region around the nearby cluster NCG 2264 is still expanding and its role in the collision is examined. However, we cannot rule out the idea that the collision arises mostly from the global collapse of the cloud.

Conclusions. The (sub-)filament-scale observables examined in this paper reveal a collision between G202.3+2.5 sub-structures and its probable role in feeding the cores in the junction region. To shed more light on this link between core and filament evolutions, one must characterise the cloud morphology, its fragmentation, and magnetic field, all at high resolution. We consider the role of the environment in this paper, but a larger-scale study of this region is now necessary to investigate the scenario of a global cloud collapse.