Dynamical histories of the IC 348 and NGC 1333 star-forming regions in Perseus

Abstract

We present analyses of the spatial distributions of stars in the young (1-3 Myr) star-forming regions IC 348 and NGC 1333 in the Perseus giant molecular cloud. We quantify the spatial structure using the Q-parameter and find that both IC 348 and NGC 1333 are smooth and centrally concentrated with Q-parameters of 0.98 and 0.89, respectively. Neither region exhibits mass segregation (Λ _MSR = 1.1^{+0.2}_{-0.3} for IC 348 and Λ _MSR = 1.2^{+0.4}_{-0.3} for NGC 1333, where Λ_MSR ∼ 1 corresponds to no mass segregation) nor do the most massive stars reside in areas of enhanced stellar surface density compared to the average surface density, according to the Σ_LDR method. We then constrain the dynamical histories and hence initial conditions of both regions by comparing the observed values to N-body simulations at appropriate ages. Stars in both regions likely formed with subvirial velocities that contributed to merging of substructure and the formation of smooth clusters. The initial stellar densities were no higher than ρ ∼ 100-500 M_⊙ pc^-3 for IC 348 and ρ ∼ 500-2000 M_⊙ pc^-3 for NGC 1333. These initial densities, in particular that of NGC 1333, are high enough to facilitate dynamical interactions that would likely affect ∼10 per cent of protoplanetary discs and binary stars.