The Research Based On LAMOST Spectra About Radial Velocity Precision

Wavelength of spectral lines in a stellar spectrum is always shifted caused by Doppler effects. By measuring the values of shifts, radial velocity of a star could be calculated. If large amount of stellar spectra obtained, the kinematic feature of our Galaxy, the Milky Way will be estimated, which consisted of hundreds of billion stars.LAMOST telescope has the highest efficiency to gather spectra in the world, which can correct 4000 targets each observing, can get 1 to 20,000 target spectra each observing night. Such huge amounts of data, it's impossible to check the radial velocity precision by measure spectra lines. So we analyze various factors of spectra which can impact the precision of radial velocity, by simulating LAMOST spectra.The main works of this paper are as follows:(1) Different temperatures for different types of stellar spectra, We simulate the theory spectra and statistical analysis to test the error when calculation the radial velocity, which introduced by the cross-correlation algorithm itself and the minimum resolution of the instrument and data sampling rate and so on. The results confirmed that the choice of cross-correlation algorithm is reliable and has high precision.(2) The reasons for Spectra in the wavelength calibration are complex, nonlinear of instrumental, the error of fitting light spectrum emission line position, error callused by dispersion curve fitting and so on. These factors together, in LAMOST wavelength calibration, it will produce a zero error about 7km/s and a random error about 15km/s. How about the impact this error on radial velocity calculation, this paper has been simulated.(3) The spectra of LAMOST with its special efficiency curve, we analyze the impact of LAMOST efficiency curve on calculate radial velocity. We simulation LAMOST efficiency curve, add to theory spectrum and found that the blue part of the efficiency curve for calculate radial velocity have a major impact, the higher the temperature, the greater impact.(4) Construct LAMOST spectrum using theoretical spectrum, that is, add efficiency curve and noise to the theory spectra. With different SNR, the radial velocity error is to reduce the signal to noise ratio increases with the trend, but only slightly.