(Proposal ID) S16A-141

(PI) Takagi, Yuhei

(Proposal Title)
Evolution of Stars and Disks in the rho Ophiuchus Cloud

(Abstract)
We propose a high-resolution near-infrared spectroscopic observation to 
determine the ages of pre-main sequence stars in rho Ophiuchus (rho Oph) 
molecular cloud. We established the age determination method of pre-main 
sequence stars based on the surface gravity determinations using equivalent 
width ratios (Takagi et al. 2010, 2011). Calculating the equivalent width 
ratio of nearby absorption lines allows us to determine the surface gravity 
of young stars with no contamination by the uncertainties of distance, 
extinction, and veiling. In our previous work, we derived the disk dissipation 
timescale of eight pre-main sequence stars in the rho Oph cloud. The targets 
in the previous study was limited to stars located in the surface area of the 
molecular cloud. In order to reveal the detailed star forming process in the 
rho Ophiuchus cloud, further observations of young stars in the inner part of 
the cloud is needed. In this observation, we will determine the ages of 16 low 
mass pre-main sequence stars by using the equivalent width of Sc and Na in 
K-band. The result of this observation will reveal the star-formation process 
in the rho Oph cloud.