Catherine Zucker edited sectionMethdology_To.tex  about 9 years ago

Commit id: de5d6241972a99f5022f8cdc5d8df42eed7b6779

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Of the four remaining filaments that do not meet all six criteria---BC\_24.96-0.17, BC\_21.25-0.15, BC\_11.13-0.12, and BC\_357.62-0.33---all of them fail criterion 6 (aspect ratio $\ge 50:1$). As our criterion 6 does not allow for projection effects in imposing an aspect ratio limit, we emphasize that those filaments lying more tangential to our line-of-sight will appear foreshortened, and could very well meet the 50:1 minimum limit if projection effects were removed. Two of these filaments BC\_24.96-0.17 and BC\_357.62-0.33 show particular promise, both lying within 1-2 pc of the physical Galactic midplane. The third filament, BC\_11.13-0.12, dubbed "the snake", has been well-studied   In summary, it is important to emphasize that some of the above criteria will likely be modified in the long run, as we learn more about the Skeleton of the Milky Way. Given our limited a priori knowledge of the Galaxy's structure, it is presently easier to confirm Bones that are spine-like, lying along arms with velocities predicted by extant modeling (criteria 1, 5), and harder to find spurs off those arms or inter-arm features (e.g. BC\_335.31-0.29), the velocities of which are hard to predict well. Similarly, since criterion 6 does not allow for projection effects in imposing an aspect ratio limit, bones which otherwise meet all criteria could fail due to their unfavorable orientation if they are oriented more perpendicular  with respect to the Earth. sun.  As we learn more about spiral structure from simulations and modeling, these criteria will also be adjusted to allow for Bone-like features that represent spurs, inter-arm structures, and/or foreshortened structures lying close to our line of sight.