密近成對星系及其恆星生成率之研究 Close galaxy pairs and their star formation rates

Date
2009
Authors
王斌威
Wang Pin-wei
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Abstract
這篇論文主要是探討交互作用星系中有哪些物理量會影響星系中的恆星生成率,而在本論文中我們是利用密近成對星系來當作研究樣本。至今,根據前人的工作我們可以知道,星系的形成及演化和星系間的交互作用至為相關,雖說其中有許多物理機制,我們到目前仍未通盤了解。而此篇文章則是先從星系中的恆星生成率的變化量來當作一個探討交互作用星系的切入點,因為基本上我們相信恆星生成活動的活躍與否和交互作用的激烈程度有一定的關聯。至於我們的資料來自兩大部份,一為可見光和紅外波段的觀測數據,另一方面使用大型宇宙學模擬所得出的星系樣本;而我們所專注的物理量主要為星系間的距離變化、成對星系間的質量比和在大尺度空間下的星系密度對於恆星生成率的影響,並比較彼此物理量在不同的時期所伴演的重要性順序為何。此外,成對星系的觀測會受限於儀器上的解析力以及靈敏度和視線方向上投影效果的污染,於是在大型高解析高靈敏度的成對星系巡天觀測運作之前,我們也先利用模擬成對星系的樣本幫助我們來初步量化投影效應所造成的影響,並估計出有多少比例的的密近成對星系仍未被偵測出來。
We focus on which physical factors would enhance star formation rate (SFR) in different stages of interacting galaxies and detection rate of this systems, especially in close galaxy pairs. Recently, previous studies suggest that these issues could account for the origin in formation and evolution of galaxies; even these questions are still unclear. Throughout our thesis, we compiled observational data extracted from IRAS sample and CFA2 survey in infrared and optical, respectively. In addition to the observational data, the output of Millennium Run (MR), the largest N-body simulation project in cosmology is also adopted. Basically, three main physical factors were considered in our analysis, including separation, mass ratio and environmental density around Mpc scale of galaxy pairs and correlations between these factors in galaxies with different SFR. We discover that mass ratio are more important than separation to enhance star forming activity in galaxy pairs, and low SFR galaxy pairs tend to be located in high galaxy density region in Mpc scale. Besides, observations of detecting close galaxy pairs or merging galaxy always suffer either or both limitations of sensitivity and angular resolution, whereas the false detection is caused by line of sight contamination. Before large enough surveys with high angular resolution available, the probably distributions of pair separation and flux, though preliminary, can be discussed from currently work. We find that the contamination is over 55% when separation of galaxy pair is over 50 kpc, and can be reduced to 25% when separation of pair is smaller than10 kpc.
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Keywords
交互作用星系, 星系演化, 恆星生成率, 成對星系, interacting galaxies, star formation rate, galaxy pair
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