Transcript Performance and sensitivity of Low Resolution Spectrographs for LAMOST

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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 = 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″
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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
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)
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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 Xinglong Station
In laboratory
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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
•3700 – 9000 Å
R ~ 1000 / 2000
•Medium-resolution
mode
•5100 – 5500 Å

8900 Å
8300 –
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32 CCD Detectors
•E2V /
England
•Chinese Company
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Image quality of blue band for low resolution configuration
R=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
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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 (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)
• ……………………………………
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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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• 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
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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
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Thank You！
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