近邻星系中恒星形成区及星族特性二维分布的研究

发布时间：2018-01-22 14:32

本文关键词： 近邻星系恒星形成 HⅡ区多波段观测星族合成尘埃消光星系演化　出处：《中国科学技术大学》2013年博士论文　论文类型：学位论文

【摘要】：星系有丰富的形态,常见的有椭圆星系、旋涡星系、和不规则星系,其中包含了恒星,星际介质如气体、尘埃,及暗物质成分。传统研究中将星系作为一个点源,获得一条光谱,但星系实际是一个延展的面源,不同区域性质各不相同。研究星系中物理性质的二维分布能为星系演化提供有效约束。本论文利用星系中多个恒星形成区光谱和星系多波段图像数据,结合星族合成方法,开展了近邻星系二维分布的研究。近邻星系是研究星系形成、结构和演化的理想研究对象,也为星系形成和演化理论提供了最丰富的观测约束。对近邻星系中HⅡ区的光谱观测已有多年历史。但以前的工作主要是对单个星系中少量几个HⅡ区的观测。我们提出了“近邻星系恒星形成区光谱观测研究”计划,开展了对20个近邻大星系中不同区域的多个恒星形成区的光谱观测。论文第二章中,我们对该课题的科学目标、选源判据、观测策略和观测情况进行了较为详细的描述。利用这些恒星形成区的光谱数据,结合多波段图像数据,可开展星系尘埃消光、恒星形成率、金属丰度和星族特性二维分布等方面的研究,加深对星系形成和演化物理过程的整体认识。在第二章第4节中,我们对其中一个星系NGC2403中HⅡ区进行了光谱分析。(1)我们首先考察了HⅡ区中心电离星团的有效温度,以及周围星际介质的电子密度。中心电离源的有效温度Teff～40000K。云团中的电子密度接近于低密度极限。(2)利用[NⅡ]/[OⅡ]vs.[OⅢ]／[OⅡ]发射线线比诊断图,我们区分了电离参数和金属丰度之间的简并关系。对于单个星系中的HⅡ区样本,电离参数有较宽的变化范围。不同的金属丰度定标指针与电离参数之间存在明显的相关关系。R23随电离参数的变化较不明显,因此是一个更好的指针。(3)使用R23经验的定标关系,我们可以得到星系中不同位置HⅡ区中的氧丰度,其径向梯度为-0.045±0.001dex.kpc-1。(4)最后,由EW(Hα)可以估计HⅡ区中的星族年龄为2.5-7Myr。论文第二部分介绍了我们利用紫外—光学一红外多波段数据对一个近邻的Scd型星系M101进行的空间可分辨研究。利用演化的星族合成模型,我们给出了星系中年龄、金属丰度、尘埃消光、恒星形成时标的二维分布图像及径向分布。(1)利用IRX-AFUV关系,我们引入了一个2级参数：恒星诞生率b,从而使IRX-AFUV关系可以应用于年老成分的星族。我们利用IRX-AFUV关系有效的降低了参数之间的简并。(2)M101整体的尘埃消光约0.24星等,并存在明显的径向趋势。我们对比了从恒星连续谱得到的恒星消光和从HⅡ区得到的气相消光。我们拟合了这一经验关系为AVstar=0.32(±0.01)AVneb+0.06(±0.01)。(3)我们得到M101中恒星金属丰度梯度为-0.011±0.006dex.kpc-1,比从HⅡ区得到的气相金属丰度更平一些。(4)我们发现不论从年龄或是颜色梯度都可以将M101中星系盘分成两个不同的成分。内盘年龄变化较陡,而外盘年龄分布较平。(5)我们认为真实星系中假设一种恒星形成时标过于简单,不同区域应当用不同的恒星形成时标来描述。对M101而言,恒星形成时标由内向外逐渐增大。在中心核球区域恒星形成时标更类似于椭圆星系,而在外盘区域恒星形成时标更类似于晚型的旋涡星系。通过以上星族特性分析,M101中的核球由年轻的、富尘埃的、金属富的星族成分主导,预示着有近期的恒星形成。具有恒星形成活动特征、转动速度高、速度弥散小、表面亮度轮廓类似于指数形式,都符合伪核球特征。
[Abstract]:The galaxy have rich forms, common are elliptical galaxies, galaxies, and irregular galaxies, including stars, interstellar medium such as gas, dust, and dark matter component. Galaxy traditional research will be a point source, get a spectrum, but the galaxy is actually an extension of the source, different the regional nature is different. The physical properties of galaxies in the two-dimensional distribution can provide effective constraints for the evolution of galaxies and Galaxy spectra. Multi band image data to form a plurality of stars and galaxies in this paper, combined with the population synthesis method to carry out the research in neighboring galaxies two-dimensional distribution.
Is the study of neighboring galaxy galaxy formation, ideal research object structure and evolution, but also for galaxy formation and evolution theory provides the most abundant observational constraints on H II. The spectroscopic observations of nearby galaxies have a long history. But the previous work is mainly a few observations of the H II single galaxy. We put forward the "neighboring galaxy star formation plan observation" area spectrum, spectral observations carried out a number of stars in different regions of 20 neighboring galaxies formed in the area. In the second chapter of this thesis, we on the scientific objectives of the project, the source selection criterion, observation method and observation is described in detail. The spectral data using these star forming region, combined with multi band image data, can carry out galactic dust extinction, star formation rate, abundance and population characteristics of metal two-dimensional distribution of the deepening on the formation of galaxies And the overall understanding of the evolutionary physical process.
In the second chapter, in section fourth, we performed a spectral analysis of the H II region of a galaxy NGC2403. (1) we first investigate the effective temperature H II Center ionization clusters, and the surrounding interstellar medium electron density. The effective temperature Teff ~ center ionization electron density of 40000K. is close to the cloud the low density limit. (2) using [N II]/[O II]vs.[O III] / [O II] emission line than the diagnosis chart, we distinguish between the ionization parameters and metallicity degeneracy. For a single galaxy in the H II sample, with a wide range of ionization parameters change. Change is not the same metallicity calibration of the pointer and the ionization parameters have obvious correlation between.R23 with ionization parameters is not obvious, so it is a pointer to a better. (3) using the R23 experience scaling relation, we can get the oxygen abundance of H II galaxies in different positions in the radial direction. Gradient of -0.045 + 0.001dex.kpc-1. (4) finally, by EW (H alpha) can be estimated by H II in new age is 2.5-7Myr.
The second part introduces our using the Scd Galaxy M101 UV optical infrared multi band data to a neighbor of the spatial resolution. Using stellar population synthesis model of evolution, we give the galaxy age, metallicity, dust extinction, star formation time scales of the two dimensional image and radial distribution. (1) the use of IRX-AFUV, we introduce a class 2 parameters: the star birth rate of B, so that IRX-AFUV can be applied to the old component of the relationship between population. We use IRX-AFUV to reduce the relationship between parameters and Jane. (2) the overall M101 dust extinction about 0.24 magnitude, and has a radial trend. We compared the continuous spectrum obtained from the stars and stellar extinction from H II gas extinction. We fitting this experience for AVstar=0.32 (+ 0.01) AVneb+0.06 (0.01). (3) we get M101 The stellar metallicity gradient of -0.011 + 0.006dex.kpc-1, is obtained from the H II region of the gas metallicity flatter. (4) we found that regardless of the age or color gradient can be M101 of galactic disk is divided into two different components. The change of age is steep, and the outer disk (age distribution is flat. 5) we think real galaxies assume a star formation time scale is too simple, should be used in different regions of different star formation time scales to describe. For M101, the star formation time scales from the inside to the outside gradually increased. In the center of the nuclear region of star formation time scales the ball more similar to elliptical galaxies, and scale vortex the galaxy is more similar to the late type is formed in the outer region of the star. The population characteristic analysis, M101 nuclear ball by the young, rich dust, metal rich stellar populations of the dominant, indicating that the recent star formation. With star formation activities The rotation speed is high, the velocity is small, the surface luminance contour is similar to the exponential form, and all conforms to the pseudonucleus characteristics.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：P15

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