A Three-Dimensional Analysis of the NGC 1977 Cluster with Gaia DR3 and Spitzer

NGC 1977 is a far-ultraviolet radiation environment significantly weaker than that of the famous Orion Nebula Cluster (ONC) a short distance to the south. Because the effects of this type of environment, which may be common in nearby star-forming regions, on circumstellar material and cluster properties has not been extensively studied, NGC 1977 is a region of particular interest for a deeper understanding of star formation processes. The high population of young stars in the area surrounding NGC 1977 introduces a degree of uncertainty in its cluster’s extent. Gaia’s Data Release 3 allows us to investigate the cluster membership and properties using this new data of unprecedented accuracy.

We present an analysis of the three-dimensional structure of the cluster and a preliminary analysis of the members’ stellar characteristics. We crossmatched Gaia sources to photometric information from Spitzer and 2MASS, and used these data to investigate the cluster size, member distribution, K-luminosity function, and infrared excess fraction (an indicator of circumstellar disks). We find that the size of the cluster and the distribution of cluster sources agrees with the discovery of an expanding bubble around the region by Pabst et al. (2022). Further analysis of the cluster’s history via source motion may support the notion that the cluster could have been formed by feedback from the Orion-BB event hypothesized by Großschedl et al. (2020), especially considering the correlation between the proper motions of the ONC and NGC 1977.