An 80 pc Long Massive Molecular Filament in the Galactic Mid-Plane

Conference paper
Part of the Astrophysics and Space Science Proceedings book series (ASSSP, volume 36)


The ubiquity of filaments in star forming regions on a range of scales is clear, yet their role in the star formation process remains in question. We suggest that there are distinct classes of filaments which are responsible for their observed diversity in star-forming regions. An example of a massive molecular filament in the Galactic mid-plane formed at the intersection of UV-driven bubbles which displays a coherent velocity structure (< 4 km s−1) over 80 pc is presented. We classify such sources as Massive Molecular Filaments (MMFs; M \(\geq \) 104M, length \(\geq \) 10 pc, \(\bigtriangleup \) v ≤ 5 km s−1) and suggest that MMFs are just one of the many different classes of filaments discussed in the literature today. Many MMFs are aligned with the Galactic Plane and may be akin to the dark dust lanes seen in Grand Design Spirals.

1 Observations

G32.02+0.06, a Massive Molecular Filament (MMF), has a coherent velocity structure over about 80 pc as traced by13CO [The Galactic Ring Survey, 4]. The molecular hydrogen mass of this filament over 80 pc is 2 × 105M in13CO and 3 × 104M in 1.1 mm dust continuum emission [The Bolocam Galactic Plane Survey, 1]. This MMF exhibits a uniform velocity field ( < 4 km s−1) over 80 pc and is parallel to the Galactic Plane. It appears to be a ridge formed at the intersection of two UV-driven bubbles.

G32.02+0.06 has been shaped by older generations of massive stars. At least three 10–50 pc diameter bubbles, likely old HII regions, each of which contain at least several massive stars appear to have compressed this cloud and created its various loops and bends. More details on the large-scale environment of this source are presented in [2] (Fig. 1).
Fig. 1

Left: An image in13CO of the Massive Molecular Filament (MMF) G32.02+0.06. Right: A position velocity cut in13CO along the spine of the filament G32.02+0.06 as traced by the black line in the left panel

2 Interpretation and Discussion

Nessie [3] is another such MMF; it too exhibits coherent ( < 3.4 km s−1) velocity structure over about 80 pc and has a total mass of about 104M as traced by dense gas, comparable to G32.02+0.06. Nessie is also parallel to the Galactic Plane, but slightly offset in latitude from the mid-plane (\(\vert b\vert \sim -0.{4}^{\circ }\)).

There are at least a handful of other MMFs aligned with the Galactic Plane (Tackenberg et al., submitted). If a majority of MMFs are aligned with the Galactic Plane this indicates that Galactic processes such as shear and spiral density waves are more important than super-bubbles in their formation. Their alignment with the Galactic Plane is analogous to dark dust lanes along spiral arms seen in face-on galaxies.

G32.02+0.06 represents just one example of an MMF in the Galactic mid-plane formed by the compression of previous generations of massive stars. We classify such filaments (M \(\geq \) 104M, length \(\geq \) 10 pc, \(\bigtriangleup \) v \(\leq \) 5 km s−1) as MMFs and suggest that they represent just one category of the oft-discussed “filaments” in the literature of late.


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Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  1. 1.Harvard-Smithsonian Center for AstrophysicsCambridgeUSA
  2. 2.Center for Astrophysics and Space AstronomyUniversity of ColoradoBoulderUSA

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