Prague Relativistic Astrophysics

Zeinab Khorrami

I will present the photometric analysis of the core of two young massive clusters, R136 and NGC3603, on the basis of HST data in the visible and the VLT high dynamic imaging that we obtained in the infrared thanks to the SPHERE focal instrument operated since 2015 and its extreme Adaptive Optics. In an extensive photometric study of these data we discovered a significantly larger number of faint low-mass stars in the core of both these clusters compared to previous works. These stars are often detected in the vicinity of known massive bright objects. By comparing HST and SPHERE measures, NGC3603 does not show any signature of mass segregation in its core since the MF slope of the very core and the next radial bin are similarly flat and agree well with the MF found in previous works of the outer regions. On the other hand R136 is partially resolved using the SPHERE/IRDIS mode with most of the massive stars having visual companions. Considering the spectroscopic and photometric errors on the extinction and the age of cluster members, I estimate a mass range for each detected star. The MF is plotted at different ages with given errors on stellar masses. Finally I demonstrate that we need more resolution to go further on studying R136 which is 7-8 times further than NGC3603.