Planetary nebulae in the inner Milky Way II: the Bulge-Disk transition
  In this work, a sample of planetary nebulae located in the inner-disk and bulge of the Galaxy is used in order to find the galactocentric distance which better separates these two populations, from the point of view of abundances. Statistical distance scales were used to study the distribution of abundances across the disk-bulge interface. A Kolmogorov-Smirnov test was used to find the distance in which the chemical properties of these regions better separate.The results of the statistical analysis indicate that, on the average, the inner population has lower abundances than the outer. Additionally, for the $\alpha$-elements abundances, the inner population does not follow the disk radial gradient towards the galactic center. Based on our results, we suggest a bulge-disk interface at 1.5 kpc, marking the transition between the bulge and inner-disk of the Galaxy, as defined by the intermediate mass population. 
O. Cavichia, R. D. D. Costa, and W. J. Maciel
astro-ph.GA