SDSS-IV MaNGA: A serendipitous observation of a potential gas accretion
  event
  The nature of warm, ionized gas outside of galaxies may illuminate several
key galaxy evolutionary processes. A serendipitous observation by the MaNGA
survey has revealed a large, asymmetric H$\alpha$ complex with no optical
counterpart that extends $\approx8"$ ($\approx6.3$ kpc) beyond the effective
radius of a dusty, starbursting galaxy. This H$\alpha$ extension is
approximately three times the effective radius of the host galaxy and displays
a tail-like morphology. We analyze its gas-phase metallicities, gaseous
kinematics, and emission-line ratios, and discuss whether this H$\alpha$
extension could be diffuse ionized gas, a gas accretion event, or something
else. We find that this warm, ionized gas structure is most consistent with gas
accretion through recycled wind material, which could be an important process
that regulates the low-mass end of the galaxy stellar mass function.
