Systematic survey of low mass members of young, nearby moving groups down to the brown dwarf range

• PI : ARan Lyo (arl@kasi.re.kr, KASI)
• co-Is : Jinhee Lee (The University of Georgia), Inseok Song (The University of Georgia)
• Summary : Nearby Young Moving Groups (NYMGs), co-moving and co-evolving loose stellar associations, are very important for various reasons and have been a hot topic of the contemporary astronomy (see the IAU symposium 314). Their proximity and youth facilitate the development of low-mass stellar evolutionary models and study of exoplanets. While a simple mass function analysis expects to uncover thousands of low mass members, the currently known members are mostly earlier spectral types than M0. Using Bayesian statistics, we can select highly probable kinematic M-type NYMG candidate members, and when combined with the imminent release of Gaia data (DR1 release: Sep 15th), youth confirmed candidate members (from Color-Magnitude diagrams) can be very effectively selected. Accurate radial velocities of candidate members obtained from IGRINS will allow us to fully calculate 7 parameters (X,Y,Z,U,V,W, and age) which will in turn confirm memberships. This project will expand the list of known low mass members by at least 10 times. With confirmed NYMG members at various ages, some gravity sensitive spectral features from IGRINS spectra such as Na I at 2.2 um can be set up as an efficient age ladder system for general use by the community. 

IGRINS Survey of Young Stellar Objects

• PI : Jae-Joon Lee (leejjoon@kasi.re.kr, KASI)
• co-Is : A-Ran Lyo, Jongsoo Kim (KASI), Jeong-Eun Lee, Sunkyung Park, Sung-Yong Yoon (KHU)
• Summary : We propose to undertake a survey of young stellar objects (YSOs) with IGRINS, which provides revolutionary spectral grasp (simultaneous coverage of H & J) at high spectral resolution of 40,000. We will observe YSOs in wide ranges of age, luminosity, and mass (from Class I to wTTSs, and from low-mass TTSs to Herbig Ae/Be stars and massive YSOs) with IGRINS. It is meant to provide a complete inventory of high resolution spectra of YSOs in various evolutionary stages and masses. The data will enable us to study various properties of protostars, their disks and outflows. A single IGRINS exposure yields spectra at resolution 45,000, covering from 1.45 to 2.5 μm; they provides various photospheric absorption lines with which we can measure effective temperature and surface gravity. We will also be able to estimate the magnetic field strength of some of our target sources. Emission lines of atomic hydrogen, CO and NaI trace their disks, and emission lines of H2 or [Fe II] indicate shocked gas from the outflows. Based on the highly successful IGRINS YSO survey program at the McDonald 2.7m Harlan J. Smith Telescope, we will extend our survey targets to more faint and embedded objects. As we did at McDonald, we plan to coordinate our YSO program with the UT YSO program.