Morphology of Open Clusters NGC 1857 and Czernik 20 using Clustering
  Algorithms
  The morphology and cluster membership of the Galactic open clusters - Czernik
20 and NGC 1857 were analyzed using two different clustering algorithms. We
present the maiden use of density-based spatial clustering of applications with
noise (DBSCAN) to determine open cluster morphology from spatial distribution.
The region of analysis has also been spatially classified using a statistical
membership determination algorithm. We utilized near infrared (NIR) data for a
suitably large region around the clusters from the United Kingdom Infrared Deep
Sky Survey Galactic Plane Survey star catalogue database, and also from the Two
Micron All Sky Survey star catalogue database. The densest regions of the
cluster morphologies (1 for Czernik 20 and 2 for NGC 1857) thus identified were
analyzed with a K-band extinction map and color-magnitude diagrams (CMDs). To
address significant discrepancy in known distance and reddening parameters, we
carried out field decontamination of these CMDs and subsequent isochrone
fitting of the cleaned CMDs to obtain reliable distance and reddening
parameters for the clusters (Czernik 20: D = 2900 pc; E(J-K) = 0.33; NGC 1857:
D = 2400 pc; E(J-K) = 0.18-0.19). The isochrones were also used to convert the
luminosity functions for the densest regions of Czernik 20 and NGC 1857 into
mass function, to derive their slopes. Additionally, a previously unknown
over-density consistent with that of a star cluster is identified in the region
of analysis.
