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Scientific Goals

Using these SEDs observed from U-band Survey and the Pan-STARRS Survey, we can achieve the scientific goals below:

1. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project is one of the National Major Scientific Projects undertaken by the Chinese Academy of Science. LAMOST is a quasi-meridian reflecting Schmidt telescope laid down on the ground with its optical axis fixed in the meridian plane. The aperture of LAMOST is 4m, enabling it to obtain the spectra of objects as faint as down to 20m.5 with an exposure of 1.5 hour. Its focal plane is 1.75m in diameter, corresponding to a 5 deg field of view, may accommodate as many as 4000 optical fibers. So the light from 4000 celestial objects will be led into a number of spectrographs simultaneously. Thus the telescope will be the one that possesses the highest spectrum acquiring rate in the world. The U-band Sky Survey will supply the input source catalogue for LAMOST;

Fig.1 The LAMOST Telescope in China.

2. Since different kind of objects such as stars, galaxies, AGN and quasars can be identified in the color-color diagram, Drs Xiaohui Fan and Xuebing Wu hope to find some quasar candidates. The following figure from Richards et al. (2002) shows the locations of different type of objects in the color color diagram.

Fig.2 Different symbols represent different kind of objects. The black points and contours are stellar sources with i < 19.1. Dark blue (dashed) lines indicate white dwarf exclusion regions; dark blue points indicate spectroscopically confirmed white dwarfs. Similarly for Astars (light blue dashed line), white dwarf + Mstar pairs (magenta dashed line), and mid-z (2:5 < z < 3:0) quasars (green solid line). We can find that the panel which using the u-band can distinguish the different kind of object best.

3. For the detection of the red shift z<3 quasar candidates combining the photometry in other bands; As we know, the lyman alpha emission feature will be detected in Uband for the z<3 quasar.

Fig.3 The qusar spectrum.

4. To estimate the red shift of the galaxies with PhotoZ combining the photometry in other bands;
5. To find out some starburst galaxies candidates;

Fig.4 A starburst galaxy.

6. Study the galactic interaction of Andromeda and M33. As Pan-Andromeda Archaeological Survey (PandAS, PI:McConnachie), only includes the observations in g and i band on CFHT, our u band survey can provide the additional useful information for the survey. The combination can help us to analyze the age and metallicity of the halo stars / star clusters bettween the two large galalxies with the color color diagrams.

Fig.5 The study of interaction of M33 and M31. The red hatched field are u-band survey region while the black squares are the supplementary obsrvations.

7. The Xuyi Schmidt Telescope and LAMOST Digital Sky Surevy of the Galactic Anti-center (XLDSS-GAC) PI: Xiaowei Liu (Peking University/KIAA, China)
As an integral component of the planned LAMOST Experiment for Galactic Under- standing and Evolution (LEQUE), the LAMOST Galactic anti-center spectroscopic survey will survey over four thousand square degree sky area centered on the Galac- tic anti-center (|b| < 30deg, 150 < l < 210deg) and obtain medium resolution optical spectra for a statistically complete sample of several million stars distributed in a spatially contiguous area. Sample stars of the LAMOST survey of the Galac- tic anti-center will derive from an ongoing CCD imaging survey utilizing the newly built 1.0/1.2m Schmidt Telescope at the Xuyi Station of the Purple Mountain Ob- servatory. The Xuyi imaging survey will deliver high quality photometry (~ 1-2 per cent) in the SDSS g, r and i bands and astrometry (~ 0.1 arcsec) for about a hundred million stars down to limiting magnitude of fainter than 19 (10sigma) in a sky area of over six thousand square degree (3 < RA < 9 hr, -10 < Dec < +60 deg) that envelopes the sky area of the LAMOST spectroscopic survey of the Galactic anti-center, with an extension to the M31/M33 region.
This Xuyi Schmidt Telescope and LAMOST Digital Sky Survey of the Galactic Anti- center (XLDSS-GAC) will yield for the first time optical photometry and spectra for millions of stars in the Galactic disk, the defining component of disk galaxies that contains most of the baryonic material and angular momentum. XLDSS-GAC will deliver spectral and luminosity classification, radial velocity and stellar parameters (Teff , Log g, [Fe/H], and probably also alpha/Fe and C/Fe elemental abundance ratios), for each sample star. Together with the accurate proper motions and distances to be obtained with the forthcoming GAIA mission, XLDSS-GAC offers unique prospects for major breakthroughs in studies of Galactic structure. In particular, XLDSS- GAC will generate a unique data set to 1) study the stellar populations, chemical composition and kinematics of the thin and thick disks and their interface with the halo; 2) identify tidal streams and debris of disrupted dwarfs and clusters; 3) probe the gravitational potential and dark matter distribution; 4) map the distribution and extinction of the interstellar medium as a function of distance; 5) search for rare objects (e.g. stars of peculiar chemical composition, hyper-velocity stars); and 6) ultimately advance our understanding of the formation and evolution of stars and galaxies.

Fig.6 The study of Galactic anti-center field. The red hatched field are Galactic anti-center field survey region.

8. For the estimates of the metallicity of the stellar populations in the galaxies;
9. For the identification of the type of the stars in the color-color diagram combining the photometry in other bands, which can help us the control the completeness of the star type for the LAMOST observations.

Fig.7 The color color diagram of different type of stars

10. It can be helpful for the flux calibration of the LAMOST spectra.

Copyright Steward Observatory, University of Arizona and National Astronomical Observatories, Chinese Academy of Sciences, 2009, All rights reserved.