Program: GS-2023A-Q-123

The stellar initial mass function (IMF) is the mass distribution of stars with the same origin. This is an essential parameter to understand star formation process as well as the overall properties of remote galaxies. Since Salpeter first introduced the concept of mass function, a number of observational results support the idea that the IMF has a universal form. On the other hand, the deep imaging observations of several young massive clusters in the inner Galaxy revealed that they have shallow (top-heavy) IMFs, suggesting that IMFs may vary depending on the star-forming environments. These observational results have thus sparked debates on the universality of the IMF. In order to examine a variation of the IMFs, we propose medium resolution spectroscopic observation of young stellar clusters in the two pairs of galaxies, the Antennae galaxies and Whirlpool galaxy. These interacting galaxies contain active star-forming regions that form young massive clusters. Since the integrated spectral features of young stellar clusters are governed by the evolutionary stages of the most massive stars and their number ratios to lower-mass stars, the underlying IMFs can be inferred from the spectral energy distributions and the strength of the Balmer jump. Our observation and analysis will test the variation of the IMF with different environments.