星系参数计算方法的研究

发布时间：2018-01-27 04:31

本文关键词： 星系消光星系质量恒星形成率　出处：《南京大学》2015年硕士论文　论文类型：学位论文

【摘要】：我们基于简单星族合成模型(Bruzual Charlot 2003；BC03)结合星系的恒星形成历史,金属丰度,尘埃消光以及速度弥散建立了模型星系库。我们利用主成分分析法(Principle component analysis;PCA)对这些模型库星系3700到5500埃范围内的光谱提取本征谱。这些本征谱的线性组合即是我们得到的观测星系拟合光谱。这些拟合光谱涵盖了星系观测光谱中D4000,HδA等信息。此外,我们基于这种方法来估算星系的物理参数,包括：比恒星形成率(SFR/M*),z波段质光比(M*/Lz)和V波段光深(τV)等。并把估算得到的参数值与其输入值进行比较,以此来研究影响星系基本物理参数估算的两个因素。第一,模型星系库输入参数的先验分布对估算星系基本物理参数的影响。我们对输入参数之一τV采用两种不同先验分布来建立模型星系库,分别对模拟星系参数进行估算,发现通常利用星云发射线得到的临近星系τV值的分布会使计算得到的τV值在星系尘埃消光较低或较高时偏离真实分布。第二,观测星系光谱信噪比(SNR)对估算星系基本物理参数的影响。通过对添加不同程度噪声的模拟星系基本物理参数的估算,我们得到了SFR/M*、M*/Lz和τV这些参数的估算精度随信噪比的变化关系。最后,我们计算了在SDSS DR7中选择的5000个恒星形成星系的τV值,并和之前由星云发射线得到的τV值进行比较。我们发现由连续谱和吸收线得到的τV比由星云发射线得到的τV系统地小大约0.5dex,我们认为由星云发射线得到的τV反映了恒星形成区的τV,而由连续谱和吸收线得到的τV更多是恒星形成区以外恒星际介质产生的。由于恒星形成区的气体尘埃丰富,因此具有更高的消光值。我们得到的这一结果也进一步验证了Charlot Fall(2000)的双参数尘埃消光模型。
[Abstract]:We based on the simple star family synthesis model Bruzual Charlot 2003; BC03) combines the galaxy's stellar formation history, metal abundance. The model galactic library is established by dust extinction and velocity dispersion. We use principal component analysis (PCA) to analyze the model galaxies. PCA). The intrinsic spectra are extracted from the spectra of these model base galaxies in the range of 3700 to 5500 A. the linear combination of these spectra is the fitting spectra of the observed galaxies. These fitting spectra cover the observed light of the galaxies. D4000 in the spectrum. In addition, we use this method to estimate the physical parameters of galaxies, including: higher star formation rate (SFR / MN). The z band mass / light ratio (MZ) and the V band light depth (蟿 V) are compared with the input values. Two factors affecting the estimation of the basic physical parameters of galaxies are studied. The influence of the prior distribution of input parameters on the estimation of the basic physical parameters of galaxies is discussed. Two different prior distributions are used to establish the model galactic library for 蟿 V, one of the input parameters. The parameters of simulated galaxies are estimated respectively. It is found that the distributions of 蟿 V values usually obtained from nebula emission lines will cause the calculated 蟿 V values to deviate from the true distribution when the extinction of galaxy dust is low or high. The influence of SNR on the estimation of the basic physical parameters of galaxies is observed. By estimating the basic physical parameters of simulated galaxies with different noise levels, we obtain SFR / M *. The estimation accuracy of the parameters M / L z and 蟿 V varies with the SNR. Finally, we calculate the 蟿 V values of 5 000 star forming galaxies selected in SDSS DR7. Compared with the previous 蟿 V values obtained from the nebula emission line, we find that 蟿 V obtained from the continuous spectrum and the absorption line is about 0.5dex smaller than the 蟿 V value obtained from the nebula emission line. We believe that 蟿 V from the emission line of the nebula reflects 蟿 V in the star forming region. The 蟿 V obtained from the continuous spectrum and absorption line is more produced by the constant interstellar media outside the star forming region, because the gas dust in the star formation region is abundant. Therefore, a higher extinction value is obtained, which further verifies the two-parameter dust extinction model of Charlot Fallt2000).
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P152

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