LAMOST星系光谱的红移自动测量

自动测量LAMOST望远镜所产生的大量星系光谱红移，是LAMOST望远镜数据处理的关键。PCAZ的红移自动测量方法，只适用于红移值较小(一般情况不超过z＜0.2)的情况，其原因是受到所应用构建正交模板的光谱模板范围的限制。文章突破了这一限制，针对LAMOST将产生的光谱的特点，作者改进了这套方法。应用该方法到具体的观测数据中，得到了准确率超过90%的红移值。该方法的红移测量极限依赖于模板的波长范围和待测光谱蓝端的信噪比，按照LAMOST的初步设计，对z＜0.8红移，可进行准确测量。经过测量, 得出结论：(1)该方法适用于LAMOST的星系红移测量;(2)为实现巡天红移的测量，需要构造完备的不同星系的光谱模版(UV-IR);(3)蓝端信噪比大小影响对大红移的测量。

An Automated Measurement of the Galaxies Spectra of LAMOST

To measure redshifts of the marge amount of galaxies' spectra automatically is t he main goal of the data processing for the LAMOST project (Large Sky Area Multi -Object Optical Fiber Spectroscopic Telescope). A method called PCAZ can be ap plied to measure the very small redshifts (generally z<0.2) due to th e re striction of the wavelength range of the templates that are composed to make or thogonal templates. In the present article, the authors break the restriction by improvin g PCAZ method according to the characteristic of LAMOST spectra. Applying th is n ew method to the SDSS data, more than 90% of the results are correct. The maxi mum limitation for redshift measurement of this new method depends on the wave leng th range of the templates and the S/N of the blue parts of the spectra. Accordin g to the spectral feature of LAMOST, the authors can measure the galaxies with z<0.8 correctly. From the experiment the authors concluded: first, this m ethod can be used to measure the redshift of LAMOST spectra; second, the authors need to compose self-contained templates of various galaxies (UV-IR) to measu re the survey redshift; finally, the S/N of the blue end of the spectra influe nces the measurement of the large redshift.