Please use this identifier to cite or link to this item:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/63949
Title: | 多波段性質、星系光度函數以及大尺度結構群聚於450微米星系的研究 Multi-wavelength properties, luminosity functions, and clustering measurements of 450-μm-selected galaxies |
Authors: | Chen-Fatt Lim 林征發 |
Advisor: | 朱有花(You-Hua Chu) |
Co-Advisor: | 王為豪(Wei-Hao Wang) |
Keyword: | 次毫米波星系,高紅移星系,星系形成,星系演化,星系光度函數,宇宙大尺度結構,機器學習, sub-millimeter galaxy,high-redshift galaxy,galaxy formation,galaxy evolution,galaxy luminosity function,large-scale structure of universe,machine learning, |
Publication Year : | 2020 |
Degree: | 博士 |
Abstract: | 本論文的研究對象主要是在次毫米波觀測到的星系,探討它們的
物理性質,從而進一步瞭解它們的生成以及演化。這些星系是經由15 米的詹姆士克拉克麥斯威爾望遠鏡中鑲嵌的SCUBA-2 儀器觀測得到。 本論文結合了SCUBA-2 最新的大型觀測計畫(STUDIES)以及所有 SCUBA-2 在COSMOS 巡天場裡的公開資料,建構了有史以來最深的 450 微米影像,其觀測靈敏度在最深的區域大約是0.6 斯基。本論文 的第一部分探討了這些星系的物理性質,例如:紅移、恆星生成率、 恆星質量、紅外光度以及塵埃輻射溫度。對於紅移小於3 以及紅外光 度大於太陽光度十的十二次方倍的450 微米星系,其塵埃輻射溫度並沒有隨著 紅移而有所演化。但是它們的塵埃輻射溫度與其於恆星生成主星序的 距離成正向關係。此外,塵埃輻射溫度也與其可見光形態有關聯,符 合了次毫米星系中的星暴成因是藉由星系間碰撞及併吞引發的。本論 文也計算了450 微米星系的光度函數以及它們的恆星生成率密度。在 紅移0 到2 之間,大於太陽光度十的十二次方倍的450 微米星系貢獻於恆星生 成率密度逐漸提升,並主導了紅移大於2 的區間。本論文的第二部分 利用了450 微米觀測到的次毫米波星系以及K-譜帶觀測到的非次毫米 波星系做為研究的基底,並透過機器學習的分類方法發展了一個分類 器。這個機器學習的分類器可以被利用於大範圍的COSMOS 巡天場 (1.6 平方度),從而在整個COSMOS 巡天場內判斷出哪些星系是次毫 米波星系的候選星系。針對這些次毫米波候選星系在紅移0.5 到3 的 區間,本論文進行了星系的兩點相關函數的分析,從而發現它們的暈 質量大約是太陽質量的二乘十的十三次方倍。此外,它們的暈質量並沒有顯示 出強烈的紅移演化關係。本研究旨在擴大我們對次毫米波星系生成與 演化的瞭解。 In my thesis, I studied a sample of sub-millimeter galaxies (SMGs), aiming at unveiling their physical properties and providing insight in the physical processes shaping galaxy formation and evolution. I based the analysis on the 450-μm data obtained from the SCUBA-2 camera on the 15-m James Clerk Maxwell Telescope (JCMT). By combining a new SCUBA-2 imaging survey from the ongoing JCMT Large Program - SCUBA-2 Ultra Deep Imaging EAO Survey (STUDIES) and all the archival data in the CANDELS/ COSMOS field, I constructed an extremely deep single-dish image across an area of 300 arcmin^2 at 450μm (S450μm ≃ 0.6 mJy beam^-1). This image is the deepest ever observed at 450μm. In the first part of my thesis, I probed the physical properties of the 450-μm-selected galaxies, such as redshift, star-formation rate (SFR), stellar mass (M *), infrared luminosity (LIR), and dust temperature (Td). I did not find a redshift evolution in dust temperature for sources with LIR > 10^12 L⊙ at z < 3. I found a moderate correlation between the dust temperature and the deviation from the SFR–M * relation. The increase in dust temperature also correlates with optical morphology, which is consistent with merger-triggered starbursts in submillimeter galaxies. I constructed the infrared luminosity functions of the 450-μm sources and measure their comoving SFR densities (SFRDs). I discovered that the contribution of the LIR > 10^12 L⊙ population to the SFRD rises dramatically from z = 0 to 2 and dominates the total SFRD at z ≳ 2. In the second part of my thesis, I developed a machine-learning classifier using optical-to-near-infrared colors from the 450-μm-selected SMGs and a sample of K-band-selected non-SMGs. I employed the trained machine-learning classifier to the general COSMOS field (1.6 deg^2) and identified a sample of SMG candidates with similar colors to the training SMG sample. I measured the two-point autocorrelation functions and found that the SMG candidates reside in massive halos of ≃ (2+-0.5) 10^13 h^-1M⊙ across the redshift range of z = 0.5–3.0. I did not find evidence of downsizing that is suggested by recent observational studies. The work presented in this dissertation contributes to widening our understanding of the evolution of SMGs. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/63949 |
DOI: | 10.6342/NTU202000685 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 天文物理研究所 |
Files in This Item:
File | Size | Format | |
---|---|---|---|
ntu-109-1.pdf Restricted Access | 11.82 MB | Adobe PDF |
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.