The New General Catalogue designation number NGC 2264 identifies two astronomical objects as a single object: the Cone Nebula and the Christmas Tree Cluster. The Snowflake Cluster and the Fox Fur Nebula are also within this designation but are not officially included.
Astronomers investigated NGC 2264, a young star cluster, using data from ESA’s XMM-Newton and Gaia satellites. The study’s findings, which were published on the arXiv pre-print repository on November 16, shed more light on the structure of this object and may be useful in furthering our understanding of stellar evolution.
Star clusters (SCs) are large groups of stars that are gravitationally bound together. They are regarded as vital laboratories for studying the evolution of stars and clusters. SCs are also useful for studying the structure of the Milky Way.
NGC 2264 (also known as Dahm 2008) is a young (estimated to be 3-5 million years old) stellar cluster with over a thousand stellar-mass members located 2,480 light years away. It is one of the most accessible star-forming regions in the Milky Way due to its proximity and the fact that the cluster’s activity is still ongoing within its parental cloud.
We revisit the structure, dynamics, and star-forming history of NGC 2264 in order to advance our understanding of the processes that lead from molecular clouds to protostars, stellar associations, and the evolution of both.
Ettore Flaccomio
So a group of astronomers led by Ettore Flaccomio of the Palermo Astronomical Observatory in Italy studied NGC 2264 in detail. For this purpose they analyzed new X-ray data obtained with the XMM-Newton and data from Gaia’s EDR3 (Early Data Release 3). The study was complemented by datasets from various catalogs.
“We revisit the structure, dynamics, and star-forming history of NGC 2264 in order to advance our understanding of the processes that lead from molecular clouds to protostars, stellar associations, and the evolution of both,” the researchers wrote in the paper.
The available data allowed the team to create a catalog of 2,257 candidate members of NGC 2264—therefore almost twice as large as previous catalogs. Afterward, the astronomers analyzed the spatial distribution of these objects and defined new substructures in the cluster.
The scientists named four new substructures based on the surface density map of candidate members: compact S Mon(C) region, embedded Cone (C-IR), Extended Halo, and S Mon(ref) region. It was discovered that the Extended Halo contains nearly 80% of all candidate members (1,794 objects). It was also mentioned that S Mon(C) is possibly older than the surrounding region or has a significantly lower fraction of stars with disks and undergoing accretion.
The authors of the paper underlined that the identification of such a high number of candidate members in the Extended Halo significantly enlarges the known extent of NGC 2264.
“The cluster is likely even broader, but a less contaminated membership is needed in order to characterize the outer population,” the researchers explained.
In summarizing the findings, the astronomers noted that stars in the southern regions of NGC 2264 are generally younger than those in the northern regions near S Mon—a larger substructure containing the newly identified S Mon(C). They believe that star formation in this cluster began around four million years ago in the S Mon region and progressed southward, where it is still ongoing.
According to the study’s authors, the findings show that NGC 2264 is not dynamically relaxed and that its current configuration is the result of multiple dynamical processes. They went on to say that this SC is one of the best places to study the mechanisms of star and cluster formation.
