A Wave-Corrected Assessment of the Local Midplane

Abstract

As the number of known Galactic structures mounts thanks to the Gaia Space Telescope, it is now pertinent to study methods for disentangling structures occupying the same regions of the Milky Way. Indeed, understanding the precise form of each individual structure and the interactions between structures may aid in understanding their origins and chronology. Moreover, accounting for known structures allows one to probe still finer Galactic structure. In order to demonstrate, we have developed an odd low-pass filter (OLPF) which removes smaller, odd-parity structures like the vertical waves, and use the filtered data to examine the location of the Galaxy's mid-plane. We find that the radial wave identified by Xu et al. (2015) continues inward to at least the Sun's location, with an amplitude that decreases towards the inner, denser parts of the disk, consistent with a simple, qualitative simulation. Additionally, we employ the OLPF results to determine the solar offset, $z_{\odot}$, with smaller structures filtered out. We find that $z_{\odot} = 34.2 \pm 0.3$ pc.