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http://www.niaot.ac.cn Performance and sensitivity of Low Resolution Spectrographs for LAMOST Zhu Yongtian, Hou Yonghui, Hu Zhongwen Wang Lei, Wang Jianing San Diego, 27 June, 2010 http://www.niaot.ac.cn Outline • Brief introduction --LAMOST --LRSs • Test results -- Image quality -- Throughout --Wavelength coverage and resolution • Some results in early commissioning observation http://www.niaot.ac.cn LAMOST http://www.niaot.ac.cn Specification of LAMOST Effective aperture: D = 4m Focal ratio: F#= 5 field of view : 5 degrees Number of Fibers : 4000 FRD: f/5→f/4 Fiber core diameter: 320micons or 3.3″ http://www.niaot.ac.cn Specification of Low Resolution Spectrograph There are 16 LRS spectrographs •250 fibers for each spectrograph •Wavelength coverage 370nm~900nm •Resolution expected 1000~10000 http://www.niaot.ac.cn The optical layout of the LAMOST-LRS Blue band(370~590nm) R5000/10000 R1000/2000 Red band (570~900nm) R5000/10000 R1000/2000 Yongtian Zhu, Zhongwen Hu, Qingfeng Zhang, et al. Proc. SPIE 6269(2006) http://www.niaot.ac.cn Spectrograph Parameters • 16 low resolution spectrographs (LRSs) for LAMOST • 250 fibers(3.3 arcsecs) / Each spectrograph • The fibers are separated by 578μm center to center along the 144 mm height arc slit • F/4 Schmidt collimator • A dichroic beam-splitter • 4 VPH gratings/LRS (low, and medium dispersion respectively) • 2 articulating red and blue F/1.3 Schmidt cameras • field lens • Corrector mirrors • 4096×4136 EEV CCD 12μm square pixel size http://www.niaot.ac.cn in Xinglong Station In laboratory http://www.niaot.ac.cn VPH Grating sets of LAMOST-LRS http://www.niaot.ac.cn VPHG http://www.niaot.ac.cn VPH gratings wavefront quality http://www.niaot.ac.cn Resolution powers •Low-resolution mode •3700 – 9000 Å R ~ 1000 / 2000 •Medium-resolution mode •5100 – 5500 Å 8900 Å 8300 – http://www.niaot.ac.cn 32 CCD Detectors •E2V / England •Chinese Company http://www.niaot.ac.cn Image quality of blue band for low resolution configuration R=1000 http://www.niaot.ac.cn Image quality of red band for low resolution configuration (R=1000) http://www.niaot.ac.cn Image quality for medium resolution configuration (R=5000) http://www.niaot.ac.cn Image quality http://www.niaot.ac.cn Image quality (with 1.6″slit) • two dimensional spectra of arc lamp (with 1.6″slit) http://www.niaot.ac.cn Throughput • Throughput of LAMOST-LRS without considering the CCD quantum efficiency and fiber transmission loss http://www.niaot.ac.cn Wavelength coverage and resolution • • • • • • CCD can cover about 348nm(red band),234nm (blue band) The wavelength range: 365-599nm (blue band) 565-913nm(red band) The resolution at central wavelength: 1100 (at 740nm), 1040 (at 480nm) The 1D spectrum of arc lamp http://www.niaot.ac.cn The twilight sky spectra obtained by LAMOST Blue band Red band http://www.niaot.ac.cn Some observation results during the early commissioning phase (in the winter 2009) • A very bright i = 16.44 quasar in the ‘redshift desert’ discovered by LAMOST (Xue-Bing Wu1, Zhaoyu Chen1, Zhendong Jia et al.)(2010) • Eight new quasars discovered by LAMOST in one extragalatic field (XueBing Wu, Zhendong Jia, Zhaoyu Chen et al.) (2010) • LAMOST Discovers Quasars Behind the Andromeda Galaxy(Zhi-Ying Huo, Xiao-Wei Liu, Hai-Bo Yuan et al.)(2010) • Detection of New Candidates of Metal-poor Stars with LAMOST Commissioning Data (H.-N. Li, G. Zhao, N. Christlieb) (2010) • LAMOST Discovers New Planetary Nebulae in the Outskirts of the Andromeda Galaxy (Hai-Bo Yuan, Xiao-Wei Liu, Zhi-Ying Huo ) (2010) • …………………………………… http://www.niaot.ac.cn A very bright i = 16.44 quasar in the ‘redshift desert’ discovered by LAMOST (z=2.427) • Left panel: The LAMOST spectrum of SDSS J085543.40-001517.7. Right panel: The spectrum of SDSS J085543.40-001517.7 taken by the NAOC/Xinglong 2.16m telescope. The scaled SDSS composite quasar spectrum (in red color) is shown for comparison Xue-Bing Wu, Zhaoyu Chen, Zhendong Jia et al. 2010 accepted by RAA http://www.niaot.ac.cn • 8 new quasars ( 2 quasars in the redshift desert) • i magnitudes: 16.24 to 19.10 • z (redshift) 0.898 to 2.773 Eight new quasars Xue-Bing Wu, Zhendong Jia, Zhaoyu Chen et al. 2010 accepted by RAA http://www.niaot.ac.cn Detection of New Candidates of Metal-poor Stars with LAMOST • only the LAMOST blue arm spectra are shown, and the continuum has not been subtracted. Hai-Bo Yuan, Xiao-Wei Liu, Zhi-Ying Huo, et al. 2010 accepted by RAA http://www.niaot.ac.cn Thank You! [email protected]