Abstract:
It has been almost 100 years since the Shapley-Curtis debate. Today, we have fantastic images of the “spiral nebulae” Shapley wanted to leave in our Milky Way, and we are quite sure that they are external galaxies. But, our knowledge of the Milky Way’s structure is still quite fuzzy. We are buried deep within the mucky plane of the Milky Way, and hence our view of it is highly obscured. In this talk, though, I will show how the Sun’s placement just 20 or so parsecs above the geometric mid-plane of the Milky Way may afford us enough perspective to map out the Galaxy’s structure in new ways. In particular, I will focus on our study of the “Nessie” cloud, a dense feature with an aspect ratio of [hundreds:one] which we believe to be a “Bone” of the Milky Way, tracing out the centroid of a nearby piece of the Scutum-Centaurus arm. I will also show how new statistical and visualization techniques are being used to create a systematic decomposition of the Milky Way’s molecular gas. I plan to conclude with a discussion of how well, or not well, we really “know” the star formation efficiency of the Milky Way.