Star formation in young star cluster NGC 1893

Abstract

We present a comprehensive multiwavelength study of the star-forming region NGC 1893 to explore the effects of massive stars on low-mass star formation. Using near-infrared colours, slitless spectroscopy and narrow-band Hα photometry in the cluster region we have identified candidate young stellar objects (YSOs) distributed in a pattern from the cluster to one of the nearby nebulae Sim 129. The V, (V−I) colour–magnitude diagram of the YSOs indicates that majority of these objects have ages between 1 and 5 Myr. The spread in the ages of the YSOs may indicate a non-coeval star formation in the cluster. The slope of the K-band luminosity function for the cluster is estimated to be 0.34 ± 0.07, which agrees well with the average value (∼0.4) reported for young clusters. For the entire observed mass range 0.6 < M/M⊙≤ 17.7 the value of the slope of the initial mass function, ‘Γ’, comes out to be −1.27 ± 0.08, which is in agreement with the Salpeter value of −1.35 in the solar neighbourhood. However, the value of ‘Γ’ for pre-main-sequence phase stars (mass range 0.6 < M/M⊙≤ 2.0) is found to be −0.88 ± 0.09 which is shallower than the value (−1.71 ± 0.20) obtained for main-sequence stars having mass range 2.5 < M/M⊙≤ 17.7 indicating a break in the slope of the mass function at ∼2 M⊙. Estimated ‘Γ’ values indicate an effect of mass segregation for main-sequence stars, in the sense that massive stars are preferentially located towards the cluster centre. The estimated dynamical evolution time is found to be greater than the age of the cluster, therefore, the observed mass segregation in the cluster may be the imprint of the star formation process. There is evidence for triggered star formation in the region, which seems to govern initial morphology of the cluster.