Correlation of gas dynamics and dust in the evolved filament G82.65-02.00^⋆,⋆⋆

¹ Department of Physics, PO Box 64, University of Helsinki, 00014 Helsinki, Finland
e-mail: mika.saajasto@helsinki.fi
² Institut UTINAM – UMR 6213 – CNRS – Univ. Bourgogne Franche Comté, 25000 Besançon, France
³ Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan
⁴ Université de Toulouse, UPS-OMP, IRAP, 31028 Toulouse, France
⁵ CNRS, IRAP, 9 Av. Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
⁶ Laboratoire AIM, IRFU/Service d’Astrophysique – CEA/DSM – CNRS – Université Paris Diderot, France
⁷ Department of Physics, Florida State University, Tallahassee, FL 32306, USA
⁸ Institute of Physics I, University of Cologne, Germany
⁹ Finnish Centre for Astronomy with ESO, University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
¹⁰ Eötvös University, Department of Astronomy, Pázmány P. s. 1/a, 1117 Budapest, Hungary
¹¹ European Space Astronomy Centre ESA/ESAC, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
¹² Department of Physical Science, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan

Received: 3 November 2016
Accepted: 26 June 2017

Abstract

Context. The combination of line and continuum observations can provide vital insight into the formation and fragmentation of filaments and the initial conditions for star formation. We have carried out line observations to map the kinematics of an evolved, actively star forming filament G82.65-2.00. The filament was first identified from the Planck data as a region of particularly cold dust emission and was mapped at 100–500 μm as a part of the Herschel key program Galactic Cold Cores. The Herschel observations cover the central part of the filament, corresponding to a filament length of ~ 12 pc at the assumed distance of 620 pc.

Aims. CO observations show that the filament has an intriguing velocity field with several velocity components around the filament. In this paper, we study the velocity structure in detail, to quantify possible mass accretion rate onto the filament, and study the masses of the cold cores located in the filament.

Methods. We have carried out line observations of several molecules, including CO isotopologues, HCO⁺, HCN, and CS with the Osaka 1.85 m telescope and the Nobeyama 45 m telescope. The spectral line data are used to derive velocity and column density information.

Results. The observations reveal several velocity components in the field, with strongest line emission concentrated to velocity range ~[3,5] km s^-1. The column density of molecular hydrogen along the filament varies from 1.0 to 2.3 × 10²²cm². We have examined six cold clumps from the central part of the filament. The clumps have masses in the range 10−20M_⊙ (~ 70 M_⊙ in total) and are close to or above the virial mass. Furthermore, the main filament is heavily fragmented and most of the substructures have a mass lower than or close to the virial mass, suggesting that the filament is dispersing as a whole. Position-velocity maps of ¹²CO and ¹³CO lines indicate that at least one of the striations is kinematically connected to two of the clumps, potentially indicating mass accretion from the striation onto the main filament. We tentatively estimate the accretion rate to be Ṁ = 2.23 × 10^-6M_⊙/ yr.

Conclusions. Our line observations have revealed two or possibly three velocity components connected to the filament G82.65-2.00 and putative signs of mass accretion onto the filament. The line observations combined with Herschel and WISE maps suggest a possible collision between two cloud components.