Volume 586, February 2016
|Number of page(s)||12|
|Section||Interstellar and circumstellar matter|
|Published online||05 February 2016|
A rotating helical filament in the L1251 dark cloud⋆
Hamburger Sternwarte, Universität Hamburg,
Gojenbergsweg 112, 21029
2 Ioffe Physical-Technical Institute, Polytekhnicheskaya Str. 26, 194021 St. Petersburg, Russia
3 St. Petersburg Electrotechnical University LETI, Prof. Popov Str. 5, 197376 St. Petersburg, Russia
4 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
5 Astronomy Department, King Abdulaziz University, PO Box 80203, 21589 Jeddah, Saudi Arabia
Received: 18 November 2015
Accepted: 22 December 2015
Aims. We derive the physical properties of a filament discovered in the dark cometary-shaped cloud L1251.
Methods. Mapping observations in the NH3(1, 1) and (2, 2) inversion lines, encompassing 300 positions toward L1251, were performed with the Effelsberg 100-m telescope at a spatial resolution of 40′′ and a spectral resolution of 0.045 km s-1.
Results. The filament L1251A consists of three condensations (α, β, and γ) of elongated morphology, which are combined in a long and narrow structure covering a 38′ × 3′ angular range (∼3.3 pc × 0.3 pc). Comparing the kinematics with the more extended envelope (∼61′ × 33′) emitting in 13CO, we find that: (1) the angular velocity of the envelope around the horizontal axis E → W is ΩEWCO ≈−2 × 10-14 rad s-1 (the line-of-sight velocity is more negative to the north); (2) approximately one half of the filament (combined α and β condensations) exhibits counter-rotation with ΩEWαβ ≈2 × 10-14 rad s-1; (3) one third of the filament (the γ condensation) co-rotates with ΩEWγ ≈−2 × 10-14 rad s-1; (4) the central part of the filament between these two kinematically distinct regions does not show any rotation around this axis; (5) the whole filament revolves slowly around the vertical axis S → N with ΩSNtot ≈7 × 10-15 rad s-1.
The opposite chirality (dextral and sinistral) of the αβ and γ condensations indicates magnetic field helicities of two types, negative and positive, which were most probably caused by dynamo mechanisms. We estimated the magnetic Reynolds number Rm ≳ 600 and the Rossby number ℛ < 1, which means that dynamo action is important.
Key words: ISM: clouds / ISM: molecules / ISM: kinematics and dynamics / radio lines: ISM / techniques: spectroscopic / line: profiles
FITS cube is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A126
© ESO, 2016
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.