Effects of SNRs on the measurement of spectra

In the present paper, the effects of signal-to-noise ratios (SNRs) on the measurement of 19 atomic Lick indices are analyzed. The stellar spectra of the large sky area multi-object fiber spectroscopic telescope (LAMOST) are selected under different conditions, which allows investigating the impact of SNRs on the accuracy and precision of the measurement of Lick/LAMOST indices. The experiment result shows that SNRs greatly affects the measurement of LAMOST/Lick indices in a complex manner. Normally, the precision of the measurement increases with SNRs with a linear trend and the affection of SNRs over 80 can be ignored. The proposed minimum SNRs is 25 according to the accuracy. Comparisons of the Lick indices under different conditions help to analyze the influence of SNRs on the precision of the measurements of LAMOST/Lick indices.