A comprehensive study of the young star cluster HD 97950 in NGC 3603

Abstract

I study the young massive star cluster HD,97950 located in the Galactic giant H,{sc ii} region NGC,3603. My goals are (1) to estimate the survival probability of the cluster, (2) to investigate the origin of its mass segregation, and (3) to investigate the interplay between the cluster and the surrounding interstellar medium (ISM). All the studies are done with data of the Hubble Space Telescope. I determine the cluster velocity dispersion from the stars' relative proper motions, and calculate the virial mass of the cluster. The cluster star formation efficiency is estimated to be about 50%, which suggests that the HD,97950 cluster will most likely survive as a bound cluster to gas expulsion. I apply the $Lambda$ minimum spanning tree technique to measure the mass segregation down to 30,M$_{odot}$. The high-mass stars are more segregated than low-mass stars, implying that the mass segregation in HD,97950 is mostly of dynamical origin. To improve the age determination for the cluster stars that are severely reddened by the surrounding dusty ISM, I compute a pixel-to-pixel distribution of the gas reddening, $E(B-V)_{rm g}$, associated with the cluster. The radial profiles of $E(B-V)_{rm g}$ show significant spatial variations around HD,97950. Using $UBVRI$ photometry, I estimate the stellar reddening of cluster stars. After correcting for foreground reddening, the total to selective extinction ratio in the cluster is $R_V=3.49pm0.79$. The extinction curve in the $UBVRI$ filters in the cluster is greyer than the average Galactic extinction laws, but close to the extinction law for starburst galaxies. This indicates that stellar feedback from massive stars changes the dust properties in the HD,97950 cluster in a similar way as in starburst galaxies.