The Galactic Survey in Optical and Infrared

Most of the Galactic baryons are in the form of stars which are mostly distributed in the Milky Way disk and halo. Therefore, large scale stellar survey plays an important role in the study of the Galactic structure and evolution. The most important survey bands are in the optical and near infrared(IR) in which the IR observation is extremely important for the disk and bulge regions since infrared radiation can penetrates through the interstellar dust. By analyzing the data of large scale photometric and/or spectroscopic survey in optical and infrared, one can get key parameters of stars,such as the brightness, colors, coordinates, radial velocities, chemical abundance and so on. These parameters are the basis of mapping the Milky Way structure and tracing the history of star formation and Galactic evolution as a whole.In this paper, we have summarized the main properties and scientific achievements of some famous Galactic photometric and spectroscopic survey projects. For the photometric survey, we have introduced the 2MASS and UKIDSS in infrared, and SSS, SDSS, IPHAS and XSTPS-GAC/LGL in optical. We have specifically emphasized in the XSTPS-GAC and-LGL projects which are the first large scale photometric surveys in China aiming at tracing the structure of the Milky Way disk. The XSTPS-GAC is carried out with the Xuyi 1.04/1.20 m Schmidt Telescope and SDSS g, r, i filters. From the year of 2009 to 2011, the survey has imaged a sky area of over 6000 sq.deg centered on the Galactic Anti-center, and generated a point source catalog containing about 1.0 × 108stars on the Galactic Anti-center. The survey reaches a ten-sigma detection limit of about 19 mag, with a photometric accuracy about 1%~2% for a single frame. After combining all frames, the final astrometric accuracy is expected to be about 0.06. For the spectroscopic survey, we introduce the RAVE, SEGUE, APOGEE, LEGUE, and HERMES survey projects. We concentrated on the LEGUE project, which is a survey of millions of stars in the Milky Way disk and halo using the LAMOST(also called Guo Shou Jing Telescope). The survey will obtain spectra for 2.5 × 106halo stars and 5 × 106disk stars. The formal survey has started in the fall of 2012, and have already obtained about one million stellar spectra with enough SNR. The survey is divided into three parts with diferent target selection strategies: disk, anticenter, and spheroid. The resulting dataset will be used to study the merger history of the Milky Way, the substructure and evolution of the disks, the nature of the first generation of stars through identification of the lowest metallicity stars, and star formation history through open clusters and the OB associations.In addition, we presented some upcoming Galactic survey projects, such as the GAIA project, which aims at compiling a 3D space catalogue of approximately 1% of stars in the Milky Way; the WEAVE, 4MOST and MOONS projects, which are the next generation spectroscopic survey facilities and plans as the GAIA follow-up; the LSST, which can photograph the entire available sky every few nights. All these projects are considered as the most ambitious Galactic survey projects in the next decade.