WORKING DRAFT authorea.com/249

# The Bones of the Milky Way

This is a preprint. The published article is available at the Astrophysical Journal (ApJ 797 53) (Goodman 2014). This online version, published in December 2012, is citable as an online “Authorea” preprint, and you can use the article’s URL to do that.

Abstract

ABSTRACT The very long, thin infrared dark cloud “

# Introduction

Determining the structure of the Milky Way, from our vantage point within it, is a perpetual challenge for astronomers. We know the Galaxy has spiral arms, but it remains unclear exactly how many, cf. (Vallée, 2008). Recent observations of maser proper motions give unprecedented accuracy in determining the three-dimensional position of the Galaxy’s center and rotation speed (Reid et al., 2009; Brunthaler et al., 2011). But, to date, we still do not have a definitive picture of the Milky Way’s three dimensional structure.

The analysis offered in this paper suggests that some Infrared Dark Clouds1–in particular very long, very dark, clouds–appear to delineate major features of our Galaxy as would be seen from outside of it. In particular, we study a $$>3^{\circ}$$-long cloud associated with the IRDC called “

Our analysis uses diverse data sets, but it hinges on combining those data