performance and sensitivity of low resolution spectrographs for lamost
DESCRIPTION
Performance and sensitivity of Low Resolution Spectrographs for LAMOST. Zhu Yongtian, Hou Yonghui, Hu Zhongwen Wang Lei, Wang Jianing San Diego, 27 June, 2010. Outline. Brief introduction -- LAMOST -- LRSs Test results - PowerPoint PPT PresentationTRANSCRIPT
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Performance and sensitivity of Low Resolution Spectrographs
for LAMOST
Zhu Yongtian, Hou Yonghui, Hu Zhongwen
Wang Lei, Wang Jianing
San Diego, 27 June, 2010
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Outline• Brief introduction
--LAMOST
--LRSs
• Test results
-- Image quality
-- Throughout
--Wavelength coverage and resolution
• Some results in early commissioning observation
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LAMOST
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Specification of LAMOST
Effective aperture: D = 4mFocal ratio: F#= 5field of view : 5 degrees Number of Fibers : 4000FRD: f/5→f/4Fiber core diameter: 320micons or 3.3″
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Specification of
Low Resolution Spectrograph
There are 16 LRS spectrographs
•250 fibers for each spectrograph
•Wavelength coverage 370nm~900nm
•Resolution expected 1000~10000
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The optical layout of the LAMOST-LRS
R1000/2000R5000/10000
R5000/10000
R1000/2000
Blue band(370~590nm)
Red band (570~900nm)
Yongtian Zhu, Zhongwen Hu, Qingfeng Zhang, et al. Proc. SPIE 6269(2006)
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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
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In laboratoryin Xinglong Station
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VPH Grating sets of LAMOST-LRS
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VPHG
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VPH gratings wavefront quality
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Resolution powers
•Low-resolution mode
•Medium-resolution mode
•3700 – 9000 Å R ~ 1000 / 2000
•5100 – 5500 Å 8300 – 8900 Å
•R ~ 5000 / 10000
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32 CCD Detectors
•E2V / England •Chinese Company
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Image quality of blue band for low resolution configurationR=1000
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Image quality of red band for low resolution configuration (R=1000)
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Image quality for medium resolution configuration (R=5000)
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Image quality
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Image quality (with 1.6″slit)
• two dimensional spectra of arc lamp (with 1.6″slit)
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Throughput
• Throughput of LAMOST-LRS without considering the CCD quantum efficiency and fiber transmission loss
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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
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The twilight sky spectra obtained by LAMOST
Blue band Red band
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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 (Xue-Bing 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)
• ……………………………………
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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
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Eight new quasars • 8 new quasars
( 2 quasars in the redshift desert)
• i magnitudes: 16.24 to 19.10
• z (redshift)
0.898 to 2.773
Xue-Bing Wu, Zhendong Jia, Zhaoyu Chen et al. 2010 accepted by RAA
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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