Spatially resolved study of the Local Group galaxies

Abstract

We have been investigating the metallicity dependence of star and planet formation, particularly focusing on the outer Galaxy with a Galactocentric distance ($R_g$) of $\gtrsim$15 kpc, where the metallicity is determined to be as low as $\sim$$-$1 dex. We have obtained near-infrared (NIR) images of young clusters in the outer Galaxy through the 8.2-m Subaru Telescope and have clearly resolved the cluster members with mass detection limits of $\sim$0.1 $M_\odot$. Consequently, we determined that the initial mass function (IMF) in the outer Galaxy is consistent with that in the solar neighborhood with regard to high-mass slope and IMF peak. Meanwhile, we suggested that the lifetime of protoplanetary disks is significantly shorter than that in the solar neighborhood. We also reported a metallicity dependence of the disk lifetime. Future observations with higher spatial resolution and sensitivity by using ELT will allow us to extend the spatially resolved studies on the IMF and protoplanetary disk evolution to Local Group galaxies. With high spatial resolution and sensitivity (i.e. 0.02 arcsec and $K\sim27$ mag with an adaptive optics), stars with mass of down to $\sim$0.1 $M_\odot$ can be detected and also sufficiently resolved. Based on such a study in a wider variety of environments, we can gain new insights related to environmental effects of star and planet formation.