Catherine Zucker edited sectionMethdology_To.tex  about 9 years ago

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\item{Projected aspect ratio $\ge 50:1$}   \end{enumerate}  The name and coordinates for these ten filaments, along with their "nicknames", average LSR velocities, the number of bone criteria they satisfy, and their key defining features, are listed in figure \ref{fig:candidates}. In figure \ref{fig:mass_of_bones}, we summarize physical parameters for all ten bone candidates, including estimates of distance, volume, mass, and aspect ratio. We calculate mass by \textit{estimating} an average H$_2$ column density of $2\rm{E}22 \rm{cm}^{-2}$), consistent with the minimum IRDC peak column density to be included in the \citet{Peretto_2009} catalog of 11,303 IRDCs. We plan to directly measure this quantity in follow-up studies, using the 8 $\mu\textrm{m}$ imaging data from the GLIMPSE survey to create column density and temperature maps for our candidates. We calculate distance by assuming all filaments are associated with the \citet{Dame_2011} Scutum-Centaurus model, as \ref{fig:skeleton} suggests. Two candidates, BC\_21.25-0.15 and BC_11.13-0.12 show potential association with the Norma-4kpc arm; to confirm their distances, we use the the catalog from \citet{Ellsworth_Bowers_2013}, which provides distances to 1710 molecular clouds from the BGPS survey, derived using a Bayesian distance probability density function. The \citet{Ellsworth_Bowers_2013} derived distance to BC\_11.13-0.12 agrees with our \citet{Dame_2011} distance within estimated errors, while BC\_21.25-0.15 falls slightly outside the acceptable error range. range (see table \ref{fig:mass_of_bones}).  Of the ten filaments with velocities consistent with galactic rotation, \textbf{six} of these meet all six bone criteria: \textbf{BC\_26.94-0.30, BC\_25.24-0.45, BC\_18.88-0.09, BC\_4.14-0.02, BC\_335.31-0.29, and BC\_332.21-0.04}, to varying degrees of excellence. We note that BC\_332.21-0.04 has likely been disrupted by stellar feedback, making its aspect ratio and velocity structure more difficult to define. Since we predict that all galactic bones will likely be destroyed by stellar feedback and/or galactic shear, we include it here as part of a larger attempt to build a catalog of bones at all stages of their evolution. We also include BC\_335.31-0.29, despite a velocity structure tangential to predicted fits of the Scutum-Centaurus arm. As spurs and interarm structures are likely to lie close to the physical Galactic midplane, but with velocity gradients angled with respect to predicted arm fits, we also include this filament in attempt to classify all bones potentially aligned with Galactic structure---be it spiral arms, spurs, feathers, or interarm regions.