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Abstract: The characterization of our Galaxy's longest filamentary gas features hasbeen the subject of several studies in recent years, producing not only asizeable sample of large-scale filaments, but also confusion as to whether allthese features (e.g. 'Bones', 'Giant Molecular Filaments') are the same. Theyare not. We undertake the first standardized analysis of the physicalproperties ($rm{H_2};$column densities, dust temperatures, morphologies,radial column density profiles) and kinematics of large-scale filaments in theliterature. We expand and improve upon prior analyses by using the same datasets, techniques, and spiral arm models to disentangle the filaments' inherentproperties from selection criteria and methodology. Our results suggest thatthe myriad filament finding techniques are uncovering different physicalstructures, with length ($11-269,rm,pc$), width ($1-40,rm,pc$), mass($rm3times10^3; M_odot-1.1times10^{6};M_odot$), aspect ratio(3:1-117:1), and high column density fraction ($0.2-100%$) varying by over anorder of magnitude across the sample of 45 filaments. We develop a radialprofile fitting code, $texttt{RadFil}$, which is publicly available. We alsoperform a $textit{position-position-velocity}$ ($textit{p-p-v}$) analysis ona subsample and find that while $60-70%$ lie spatially in the plane of theGalaxy, only $30-45%$ concurrently exhibit spatial $textit{and}$ kinematicproximity to spiral arms. In a parameter space defined by aspect ratio, dusttemperature, and column density, we broadly distinguish three filamentcategories, which could indicate different formation mechanisms or histories.Highly elongated 'Bone-like' filaments show the most potential for tracinggross spiral structure (e.g. arms, spurs), while other categories could belarge concentrations of molecular gas (GMCs, core complexes).

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Submission history

From: Catherine Zucker [view email]
[v1] Wed, 27 Dec 2017 18:57:07 UTC (7,434 KB)
[v2]Tue, 29 May 2018 17:12:33 UTC (6,299 KB)
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