New Open Cluster Candidates Discovered in the XSTPS-GAC Survey

TL;DR

This study reports the discovery of 24 new open cluster candidates in the Galactic Anti-center region using the XSTPS-GAC survey, along with their properties derived through isochrone fitting, enhancing the understanding of Galactic structure.

Contribution

The paper introduces a method for identifying new open cluster candidates in the GAC region using star density maps and confirms their properties with multi-band photometry, including 2MASS data.

Findings

Discovered 24 new open cluster candidates.

Reidentified 320 known open clusters.

Determined properties of new and known clusters for the first time.

Abstract

The Xuyi Schmidt Telescope Photometric Survey of the Galactic Anti-center (XSTPS-GAC) is a photometric sky survey that covers nearly 6 000 deg^2 towards Galactic anti-center in g r i bands. Half of its survey field locates on the Galactic Anti-center disk, which makes XSTPS-GAC highly suitable for searching new open clusters in the GAC region. In this paper, we report new open cluster candidates discovered in this survey, as well as properties of these open cluster candidates, such as age, distance and reddening, derived by isochrone fitting in the color-magnitude diagram (CMD). These open cluster candidates are stellar density peaks detected in the star density maps by applying the method from Koposov et al. (2008). Each candidate is inspected on its true color image composed from XSTPS-GAC three band images. Then its CMD is checked, in order to identify whether the central region stars have a clear isochrone-like trend differing from the background stars. The parameters derived from isochrone fitting for these candidates are mainly based on three band photometry of XSTPS-GAC. Meanwhile, when these new candidates are able to be seen clearly on 2MASS, their parameters are also derived based on 2MASS (J-H, J) CMD. Finally, there are 320 known open clusters rediscovered and 24 new open cluster candidates discovered in this work. Further more, the parameters of these new candidates, as well as another 11 known recovered open clusters, are properly determined for the first time.