Discovery of an open cluster with a possible physical association with a planetary nebula

Abstract

We report the discovery of a new open cluster (OC) in the Galaxy at l = 167◦ 0 and b = −1◦ 0. Its field includes the planetary nebula (PN) PK 167−0.1. We study the possible associations of the PN/OC pairs NGC2818/2818A, NGC2438/M 46 (NGC 2437), PK 6+2.5/NGC 6469, as well as of the PN PK 167−0.1 with NewCluster 1. The analyses are based on near-infrared colour–magnitude diagrams (CMDs) and stellar radial density profiles. NGC6469 is located in a heavily contaminated bulge field. The CMD morphology, especially for the latter two cases, is defined with a field-star decontamination algorithm applied to the 2MASS J, H and Ks photometry. Field decontamination for the OCs NGC2818A and M46 produced better defined CMDs and more accurate cluster parameters than in the literature. Those pieces of evidence point to M46 as physically associated with the PN NGC2438. The same occurs for the OC NGC2818A and the PN NGC2818; however, previous radial velocity arguments indicate that they are not associated. The OC NGC6469 does not appear to be associated with the PN PK 6+2.5, which probably belongs to the bulge. Finally, the distance of the OC NewCluster 1 is consistent with a physical association with the PN PK 167−0.1.