2009ApJ...697.1138J

Using an [O III] λ5007 on-band/off-band filter technique, we identify 109 planetary nebulae (PNe) candidates in the edge-on spiral galaxy M 82, using the FOCAS instrument at the 8.2 m Subaru Telescope. The use of ancillary high-resolution Hubble Space Telescope Advanced Camera for Surveys Hα imaging aided in confirming these candidates, helping to discriminate PNe from contaminants such as supernova remnants and compact H II regions. Once identified, these PNe reveal a great deal about the host galaxy; our analysis covers kinematics, stellar distribution, and distance determination. Radial velocities were determined for 94 of these PNe using a method of slitless spectroscopy, from which we obtain a clear picture of the galaxy's rotation. Overall, our results agree with those derived by CO(2-1) and H I measurements that show a falling, near-Keplerian rotation curve. However, we find a subset of our PNe that appear to lie far (∼1 kpc) above the plane, yet these objects appear to be rotating as fast as objects close to the plane. These objects will require further study to determine if they are members of a halo population, or if they can be interpreted as a manifestation of a thickened disk as a consequence of a past interaction with M 81. In addition, [O III] λ5007 emission-line photometry of the PNe allows the construction of a planetary nebula luminosity function (PNLF) for the galaxy. Our distance determination for M 82, deduced from the observed PNLF, yields a larger distance than those derived using the tip of the red giant branch technique, using Cepheid variable stars in nearby group member M 81, or using the PNLF of M 81. We show that this inconsistency most likely stems from our inability to completely correct for internal extinction imparted by this dusty, starburst galaxy. Additional observations that yield object-by-object foreground and internal extinction corrections are required to make an accurate distance measurement to this galaxy.