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  • The Skeleton of the Milky Way

    Abstract

    Recently, Goodman et al. (2014) argued that the very long, very thin infrared dark cloud “Nessie” lies directly in the Galactic midplane and runs along the Scutum-Centaurus arm in position-position-velocity (p-p-v) space as traced by lower density \(\textrm{CO}\) and higher density \(\mathrm{NH_3}\) gas. Nessie was presented as the first “bone” of the Milky Way, an extraordinarily long, thin, high-contrast filament that can be used to map our Galaxy’s ”skeleton.“ Here, we present evidence for additional bones in the Milky Way Galaxy, arguing that Nessie is not a curiosity but one of several filaments that could potentially trace Galactic structure. Our ten bone candidates are all long, filamentary, mid-infrared extinction features which lie parallel to, and no more than twenty parsecs from, the physical Galactic mid-plane. We use \(\textrm{CO}\), \(\mathrm{N_2H+}\), \(\textrm{HCO}^{+}\) and \(\mathrm{NH_3}\) radial velocity data to establish the three-dimensional location of the candidates in p-p-v space. Of the ten candidates, six also: have a projected aspect ratio of \(\ge 50\colon1\); run along, or extremely close to, the Scutum-Centaurus arm in p-p-v space; and exhibit no abrupt shifts in velocity. Evidence suggests that these candidates are marking the locations of significant spiral features, with the bone called filament 5 (”BC_18.88-0.09"