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Do cores with sharp transitions to coherence correspond to velocity-coherent fibers?---the case of Perseus B5
  • Hope How-Huan Chen,
  • Jaime Pineda,
  • Alyssa Goodman
Hope How-Huan Chen
Harvard-Smithsonian Center for Astrophysics (CFA)

Corresponding Author:[email protected]

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Jaime Pineda
Max-Planck-Institut für extraterrestrische Physik
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Alyssa Goodman
Harvard-Smithsonian Center for Astrophysics (CFA)
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Abstract

\citet{Hacar_2013} found “velocity-coherent fibers” in Taurus, by applying Friends-of-Friends (FoF) algorithm on the fitted peaks of FCRAO C\(^{18}\)O (1-0) line emission. Ever since, the velocity-coherent fibers are more than often related to the coherent cores defined by a sharp transition from supersonic velocity dispersion outside the core to subsonic velocity dispersion inside \citep{Goodman_1998}. For example, the elongated coherent core found in Perseus B5 \citep{Pineda_2010} is often treated as a velocity-coherent fiber. Here we examine the C\(^{18}\)O (2-1) line emission in Perseus B5 from IRAM 30m telescope, and compare to the GBT NH\(_3\) emission from \citet{Pineda_2010}. We find that, even though the coherent core defined by the sharp transition in velocity dispersion overlaps in the position-position-velocity (PPV) space with a velocity-coherent fiber found by applying the FoF algorithm on the C\(^{18}\)O (2-1) emission, the two structures do not match in the PPV space and have different kinematics. The result indicates that the coherent core does not always correspond to the velocity-coherent fiber, and that the structures defined by the sharp transition in velocity dispersion (coherent cores) and those defined by connection of velocity centroids in the PPV space (velocity-coherent fiber) are not the same.