Gas kinematics around filamentary structures in the Orion B cloud

¹ LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, 75014 Paris, France
e-mail: maryvonne.gerin@obspm.fr
² Chalmers University of Technology, Department of Space, Earth and Environment, 412 93 Gothenburg, Sweden
³ IRAM, 300 rue de la Piscine, 38406 Saint-Martin-d’Hères, France
⁴ Aix-Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
⁵ Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 Saint George Street, 14th floor, Toronto, ON M5S 3H8, Canada
⁶ Laboratoire de Physique de l’Ecole normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris-Cité, Paris, France
⁷ Université Paris-Saclay, Université Paris-Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
⁸ Instituto de Física Fundamental (CSIC), Calle Serrano 121, 28006, Madrid, Spain
⁹ LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, 92190 Meudon, France
¹⁰ University of Toulouse, IRIT/INP-ENSEEIHT, CNRS, 2 rue Charles Camichel, BP 7122, 31071 Toulouse cedex 7, France
¹¹ Univ. Lille, CNRS, Centrale Lille, UMR 9189 – CRIStAL, 59651, Villeneuve d’Ascq, France
¹² Univ. Grenoble-Alpes, Inria, CNRS, Grenoble INP, GIPSA-Lab, Grenoble 38000, France
¹³ Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France
¹⁴ Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
¹⁵ Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Paul Sabatier, Toulouse cedex 4, France
¹⁶ Université Paris-Cité, 75006 Paris, France
¹⁷ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
¹⁸ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138, USA
¹⁹ School of Physics and Astronomy, Cardiff University, Queen’s buildings, Cardiff CF24 3AA, UK
²⁰ Université Paris-Saclay, UVSQ, CNRS, CEA, Maison de la Simulation, 91191 Gif-sur-Yvette, France

Received: 30 August 2021
Accepted: 14 November 2022

Abstract

Context. Understanding the initial properties of star-forming material and how they affect the star formation process is key. From an observational point of view, the feedback from young high-mass stars on future star formation properties is still poorly constrained.

Aims. In the framework of the IRAM 30m ORION-B large program, we obtained observations of the translucent (2 ≤ A_V < 6 mag) and moderately dense gas (6 ≤ A_V < 15 mag), which we used to analyze the kinematics over a field of 5 deg² around the filamentary structures.

Methods. We used the Regularized Optimization for Hyper-Spectral Analysis (ROHSA) algorithm to decompose and de-noise the C¹⁸O(1–0) and ¹³CO(1–0) signals by taking the spatial coherence of the emission into account. We produced gas column density and mean velocity maps to estimate the relative orientation of their spatial gradients.

Results. We identified three cloud velocity layers at different systemic velocities and extracted the filaments in each velocity layer. The filaments are preferentially located in regions of low centroid velocity gradients. By comparing the relative orientation between the column density and velocity gradients of each layer from the ORION-B observations and synthetic observations from 3D kinematic toy models, we distinguish two types of behavior in the dynamics around filaments: (i) radial flows perpendicular to the filament axis that can be either inflows (increasing the filament mass) or outflows and (ii) longitudinal flows along the filament axis. The former case is seen in the Orion B data, while the latter is not identified. We have also identified asymmetrical flow patterns, usually associated with filaments located at the edge of an H II region.

Conclusions. This is the first observational study to highlight feedback from H II regions on filament formation and, thus, on star formation in the Orion B cloud. This simple statistical method can be used for any molecular cloud to obtain coherent information on the kinematics.