Sejong Open Cluster Survey (SOS). 0. Target Selection and Data Analysis

TL;DR

The Sejong Open Cluster Survey aims to provide homogeneous photometric data for numerous open clusters to study their properties and Galactic structure, using precise observational and calibration methods.

Contribution

This paper introduces the target selection, observational strategy, and calibration procedures for the SOS, focusing on small, sparse clusters previously unobserved.

Findings

Established criteria for target selection and data calibration.

Developed methods for reddening law and membership determination.

Provided initial data analysis for cluster distances and properties.

Abstract

Star clusters are superb astrophysical laboratories containing cospatial and coeval samples of stars with similar chemical composition. We have initiated the Sejong Open cluster Survey (SOS) - a project dedicated to providing homogeneous photometry of a large number of open clusters in the SAAO Johnson-Cousins' $UBVI$ system. To achieve our main goal, we have paid much attention to the observation of standard stars in order to reproduce the SAAO standard system. Many of our targets are relatively small, sparse clusters that escaped previous observations. As clusters are considered building blocks of the Galactic disk, their physical properties such as the initial mass function, the pattern of mass segregation, etc. give valuable information on the formation and evolution of the Galactic disk. The spatial distribution of young open clusters will be used to revise the local spiral arm structure of the Galaxy. In addition, the homogeneous data can also be used to test stellar evolutionary theory, especially concerning rare massive stars. In this paper we present the target selection criteria, the observational strategy for accurate photometry, and the adopted calibrations for data analysis such as color-color relations, zero-age main sequence relations, Sp - Mv relations, Sp - Teff relations, Sp - color relations, and Teff - BC relations. Finally we provide some data analysis such as the determination of the reddening law, the membership selection criteria, and distance determination.