The Origin of WHAM Point Source 46

Abstract

The Wisconsin Hα Mapper surveyed the entire Galactic sky in Hα (∣vLSR∣ ≲ 100 km s−1) to approximately 0.1 Rayleigh (R), albeit with a 1° beam. Reynolds et al. (2005) reported “point sources” which stood out against the Galactic background in space and velocity. Half of the sources are associated with plausible planetary nebulae and OB stars. Reynolds et al. suggested sub dwarfs for one quarter of the sources. Here, we investigate one such source, WPS 46, for which Reynolds et al. suggested the sub-dwarf PG 0931+691 to provide the source of ionization. With the Keck Cosmic Web Imager we found numerous nebular emission lines within the vicinity of WPS 46, but we failed to find Hα emission in the arc-minute vicinity of PG 0931+691. The line ratios (BPT diagram and [S ii]/Hα) combined with the morphology are more consistent with AGN or LI(N)ER-like ionization than with pure warm ionized medium or H ii region-like photoionization. Separately, we offer compelling reasons to argue that PG 0931+691 cannot be the source of ionizing power for WPS 46. We suggest that WPS 46 is associated with an intermediate velocity complex (IVC) and that Hα and nebula emission may arise as a result of a shock. We conclude by outlining a plan of action of using SDSS’s Local Volume Mapper along with deep narrow band imagery obtained by amateur astronomers to explore and study the ionized sky on sub-degree scales, in general, and specifically studies of IVC and high-velocity complexes.