2022MNRAS.510.1136P

We quantify the spatial distribution of stars for two subclusters centred around the massive/intermediate-mass stars S Mon and IRS 1/2 in the NGC 2264 star-forming region. We find that both subclusters have neither a substructured nor a centrally concentrated distribution according to the Q-parameter. Neither subcluster displays mass segregation according to the Λ_MSR ratio, but the most massive stars in IRS 1/2 have higher relative surface densities according to the Σ_LDR ratio. We then compare these quantities to the results of N-body simulations to constrain the initial conditions of NGC 2264, which are consistent with having been dense (∼ρ∼10⁴ M_☉ pc^–3), highly substructured and subvirial. These initial conditions were also derived from a separate analysis of the runaway and walkaway stars in the region, and indicate that star-forming regions within 1 kpc of the Sun likely have a broad range of initial stellar densities. In the case of NGC 2264, its initial stellar density could have been high enough to cause the destruction or truncation of protoplanetary discs and fledgling planetary systems due to dynamical encounters between stars in the early stages of its evolution.