A Preliminary Study of the Orion Nebula Cluster Structure and Dynamics

摘要: We use optical and near-infrared star counts to explore the structure dynamics of Orion Nebula Cluster (ONC). This very young (<1 Myr) cluster is not circularly symmetric in projection but elongated north-south a manner similar molecular gas distribution region, suggesting that stellar system may still reflect geometry protocluster cloud. Azimuthally averaged source compare well with simple spherically symmetric, single-mass King models. The model fits suggest inner Trapezium region should be regarded as core ONC, distinct entity sometimes advocated. estimate radius 0.16-0.21 pc central density approaches 2 × 10^4 stars pc^(-3). Adopting velocity dispersion from published proper-motion studies, virial equilibrium would require total mass within about ~4500 M_☉, slightly more than twice known population comparable estimated projected onto same sky. If ≳ 20% remaining converted into stars, thus adding binding mass, given present alone has energy close zero, ONC likely produce gravitationally bound cluster. also exhibits segregation, most massive (Trapezium) clearly concentrated toward center some evidence for degree concentration decrease decreasing down 1-2 expected general segregation. Given extreme youth compared range collisional relaxation times, segregation unlikely result relaxation. Instead, we reflects preference higher form dense, regions.