低分辨率天体光谱中呈现的双峰发射线轮廓可能反映着比较珍稀的物理现象, 如双活动星系核（AGNs）、 双超大质量黑洞（SMBH）、 喷流云与窄线区的相互作用, 也可能是光谱处理过程产生的低质量特征线。 双峰发射线轮廓一般由2个或2个以上的波峰构成, 对该特征进行提取并分析, 可作为双AGN、 星系对、 双黑洞等稀有天体更有效的搜寻依据, 从而有助于更深入地研究星系乃至宇宙的形成与演化。 提出一种新的基于相关子空间的双峰发射线特征提取与分析方法, 主要工作分为以下三部分: 首先利用稀疏差异因子δ度量双峰发射线光谱中属性差异程度, 利用KNN方法约束参与稀疏差异因子计算的光谱范围, 在此基础上, 针对LAMOST低分辨率光谱给出基于相关子空间的特征提取方法; 其次, 为了验证稀疏差异因子σ以及KNN的输入参数k对双峰发射线光谱的适应性, 选择LAMOST双峰发射线光谱样本及普通星系光谱数据, 红移范围z<0.3（确保Hα, Hβ, ［OⅢ］λλ4 959, 5 007, ［NⅡ］λλ6 548, 6 584, ［SⅡ］λλ6 717, 6 731等发射线落在LAMOST波长覆盖范围）, 获得训练集光谱总数332+332（正负样本）条, 并借助人眼检查分析该方法中的两个参数: k和δ阈值α对结果的影响, 实验表明, 当k=18, α=0.6时, 相关属性分布较密集且稀疏点较少, 结果比较理想; 最后, 对332条双峰发射线光谱特征子空间所在的波长区间、 双峰红/蓝移间隔、 双峰线强比等进行了理论分析、 测量及人眼认证的基础上, 给出了基于相关子空间的双峰发射线特征表述。 此外, 从双峰特征子空间上不同的发射线激发机制（［OⅢ］/［NⅡ］/［SⅡ］等禁线、 Hα、 Hβ等氢线）及相关特征子空间上线强关系等角度, 对样本中双峰轮廓进行了分析。

Double-peaked emission lines may reflect some rare scenes, such as binary active nucleus (AGNs), double supermassive black holes (SMBHs), interaction between jet and narrow line regions, or be low-quality spectra. Generally, at least 2 peaks are included in double-peaked emission lines, which are useful in searching rare objects such as AGNs, SMBHs, galaxypairs. It is meaningful in researching double-peaked emission lines for further studying formation and revolution of galaxies and even the universe. In this paper, a new method based on relevant subspace for extracting and analyzing of double-peaked emission line spectra is proposed. There are 3 parts in this paper: (1) Sparse difference factor δ is defined to measure attribute difference degree in spectra with double-peaked emission lines. And KNN algorithm is employed to restrain the involved spectral data. Then, characteristics extraction method for low solution spectra is proposed based on relevant subspace. (2) To test the efficient of parameters of sparse difference factor δ and k of KNN algorithm, 664 spectra are selected from LAMOST as training set, including 332 positive samples and 332 negative ones. To ensure 8 lines (Hα, Hβ, ［OⅢ］λλ4 959, 5 007, ［NⅡ］λλ6 548, 6 584, ［SⅡ］λλ6 717, 6 731) are in wavelength coverage of LAMOST, the redshift region is z<0.3. And then influence of experiment result about two parameters k and α of δ threshold is analyzed. The result indicates that distribution of relevant attributes is dense with less sparse points when k=18 and α=0.6. (3) Wavelength coverage, red/blue shift interval and line strength ratio of double-peaked emission lines in subspace are analyzed and measured theoretically. Then characteristic description of double peaks based on relevant subspace is given. Finally profiles of double peaks are analyzed according to emission excitation mechanism and line strength relationship.