KMS of Xinjiang Astronomical Observatory, CAS
| 近邻星系星族性质及恒星形成区物理性质研究 | |
| Alternative Title | The Stellar Population Properties and Physical Properties of Star Formation Regions in Nearby Galaxies |
魏鹏
| |
| Subtype | 博士 |
| Thesis Advisor | 刘祥 ; 周旭 |
| 2020 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Name | 理学博士 |
| Degree Discipline | 天体物理 |
| Keyword | 近邻星系,星系演化,星族合成,星际介质,H ii区 |
| Abstract | 星系形成与演化是现代天文学重要的研究领域，近邻星系是研究星系形成 与演化的理想天体物理实验室。恒星、气体、尘埃以及暗物质是星系的基本组 成成分。星族性质、恒星质量、气体金属丰度等是星系的重要物理参数，研究它 们的二维分布能为星系演化提供重要的观测约束。本论文利用近邻相互作用星 系对 M51-NGC5195 的多波段测光数据和恒星形成区光谱观测数据，开展星族性 质、尘埃与气相金属丰度的空间分布研究。首先，利用近邻星系 M51 及其伴星系 NGC5195 的紫外 (GALEX 和 XMM OM)、光学 (BATC 和 BASS) 和近中红外 (2MASS 和 Spitzer) 多波段图像数据，结 合演化星族合成模型，我们研究了这个相互作用系统空间解析的星族性质。我 们用观测得到的红外-紫外光度比 (IRX) 与远紫外的尘埃消光 (AFUV ) 之间的关系 来约束尘埃消光，降低参数间的简并效应。通过拟合观测和模型合成的光谱能 量分布 (SEDs)，我们获得了星族年龄、金属丰度、尘埃消光 AV 以及恒星质量面 密度的二维分布。旋涡星系 M51 中从核球延伸出来的两条巨型旋臂由年轻的且 富金属的星族构成，尘埃也聚集于此，而旋臂间的区域则是由年老的和相对更 低的金属丰度的星族组成，尘埃消光也更低。除了从 M51 延伸到 NGC5195 的旋 臂，NGC5195 的星族性质特征比较单一。整体而言，相比于 M51，NGC5195 的 星族年龄更加年老，它的核心区域尘埃较多，尘埃消光达到 1.67 mag，同时恒星 质量面密度更高。两个星系之间的近距离遭遇很可能迫使 M51 旋臂中的尘埃进 入 NGC5195 的核心。通过许多观测特征以及星族特性分析，M51 的核球是经过 长期演化形成的伪核球。星系间相互作用增强了 M51 的北旋臂上的恒星形成活 动，同时产生了可能的气体内流以及 M51 与 NGC5195 之间的物质交换。长期演 化和星系间的相互作用都可能在这一相互作用系统的演化过程中发挥重要作用。其次，利用国家天文台兴隆观测基地 2.16m 望远镜和美国 6.5m MMT 望远 镜对 M51 内的 113 个恒星形成区 (H ii) 的高空间分辨 (< 100 pc) 光谱观测数据， 结合Croxall 等 (2015) 的文献数据，我们细致的研究了这些H ii区的一系列物理 特性，包括气相尘埃、星族年龄、恒星形成率 (SFR) 面密度和气相氧丰度。通过 这些性质的空间二维分布及径向轮廓来研究 M51 的星系演化线索。M51 的气相尘埃消光呈现出微弱的径向负梯度，M51 与 NGC5195 的近距离遭遇很可能导致了 M51 中北旋臂中的尘埃消光低于南旋臂。M51 中很多H ii区的星族年龄分布在 50-500 Myr 之间，这与文献中模拟得出最近一次近距离遭遇的时间一致。恒星形成率面密度也展现出微弱的径向负梯度，这在旋涡星系中是普遍存在的。我们使用强线方法 O3N2 定标关系获得了星系不同位置H ii区的气相氧丰度，星系盘的径向梯度为 −0.08 dex Re−1，这支持了 M51 为“inside-out”的增长方式，在许多旋涡星系中比较常见。但是，我们还发现在 M51 的内部区域存在 0.26 dex Re−1的径向正梯度，可能原因包括:(1) 由于核球的恒星形成活动熄灭而导致化学增丰冻结;(2) 由于伪核球的增长和/或星系相互作用而导致气体内流进而稀释金属丰度。 |
| Other Abstract | Galaxy formation and evolution is an important research field in modern astronomy. Nearby galaxies are an ideal astrophysical laboratory for studying the galaxy formation and evolution, both observationally and theoretically. Stars, gas, dust and dark matter are the basic components of galaxies. The stellar population properties, stellar mass and gas-phase metallicity are important physical parameters of galaxies. The two- dimensional distributions of these parameters can provide key observational constraints for studying galaxy evolution. In this thesis, the stellar population properties, dust attenuation and gas-phase metallicity of nearby interacting galaxies M51 - NGC5195 are explored in details with multi-band photometric images and spectroscopic observations of H ii regions.Firstly, using multi-band photometric images of M 51 and its companion NGC 5195 from ultraviolet, optical to infrared, we investigate spatially resolved stellar population properties of this interacting system with stellar population synthesis models. The observed IRX is used to constrain dust extinction. Stellar mass is also inferred from the model fitting. By fitting observed spectral energy distributions (SEDs) with synthetical ones, we derive two-dimensional distributions of stellar age, metallicity, dust extinction, and stellar mass. In M51, two grand-designed spiral arms extending from the bulge show young age, rich metallicity, and abundant dust. The inter-arm regions are filled with older, metal-poorer, and less dusty stellar populations. Except for the spiral arm extending from M 51 into NGC 5195, the stellar population properties of NGC 5195 are quite featureless. NGC 5195 is much older than M 51, and its core is very dusty with AV up to 1.67 mag and dense in stellar mass. The close encounters might drive the dust in the spiral arm of M51 into the center of NGC 5195. There are a lot of hints indicating that the bulge of M51 is a pseudobulge formed through the secular evolution. The galaxy interaction makes more enhanced star formation in the north arms and yields possible gas inflow and material exchange between M51 and NGC 5195. Both secular evolution and galaxy interaction might play important roles on the current evolution of this interacting system.Secondly, the H ii regions in M 51 were observed using the 2.16 m telescope of the National Astronomical Observatories of the Chinese Academy of Sciences and the 6.5m Multiple Mirror Telescope with spatial resolution of less than ∼ 100 pc. We obtain a total of 113 spectra across the galaxy and combine the literature data of Croxall et al. (2015) to derive a series of physical properties, including the gas-phase extinction, stellar population age, star formation rate (SFR) surface density, and oxygen abundance. The spatial distributions and radial profiles of these properties are investigated in order to study the characteristics of M 51 and the clues to the formation and evolution of this galaxy. M 51 presents a mild radial extinction gradient. The lower gas-phase extinction in the north spiral arms compared to the south arms are possibly caused by the past encounters with the companion galaxy of NGC 5195. A number of H ii regions have the stellar age between 50–500 Myr, consistent with the recent interaction history by simulations in the literatures. The SFR surface density presents a mild radial gradient, which is ubiquitous in spiral galaxies. There is a negative metallicity gradient of −0.08 dex Re−1 in the disk region, which is also commonly found in many spiral galaxies. It is supported by the “inside-out" scenario of galaxy formation. We find a positive abundance gradient of 0.26 dex Re−1 in the inner region. There are possible reasons causing the positive gradient, including the freezing of the chemical enrichment due to the star-forming quenching in the bulge and the gas infall and dilution due to the pseudobulge growth and/or galactic interaction. |
| Pages | 118 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xao.ac.cn/handle/45760611-7/4145 |
| Collection | 研究生学位论文 |
| Affiliation | 中国科学院新疆天文台 |
| First Author Affilication | Xinjiang Astronomical Observatory, Chinese Academy of Sciences |
| Recommended Citation GB/T 7714 | 魏鹏. 近邻星系星族性质及恒星形成区物理性质研究[D]. 北京. 中国科学院大学,2020. |
| Files in This Item: | ||||||
| File Name/Size | DocType | Version | Access | License | ||
| 魏鹏.pdf（3380KB） | 学位论文 | 暂不开放 | CC BY-NC-SA | Application Full Text | ||
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