紅移介2和3偏紅且偏重星系之性質研究

Abstract

我們採用一套可以在Linux系統下進行的程式 (Hyperz) 來研究紅移介於2和3之間偏紅且偏重星系的性質研究。經由這套程式的模擬，我們計算出所有星系樣本的絕對座標顏色分佈，紅移和星系質量。畫出顏色質量分佈圖之後，我們討論了星系紅藍分界線從何時開始。我們也計算了各紅移範圍內偏紅星系的比例，再搭配其他研究者的工作，我們對星系如何演化做出了推測。我們發現星系聚合，轉換和單純老化可以解釋星系各種物理量的演化。

We use the optical and near-infrared data from GOODSN to study the properties of the red and massive galaxies .This provides the largest sample size to date for galaxies with stellar masses greater than 1010 solar mass . With Hyperz , we have the information of redshifts , stellar mass and rest frame color of our sample galaxies . By plotting the color-mass diagram , we study when the red-sequence first appears and the color bimodality appears . Besides , we also calculate the fraction of the red sequence in different redshift bins to study the evolution of the red sequence , in order to constrain the galaxy formation models . Our results show that the fraction of red sequence galaxies decreases as going to higher redshift . At z < 1 , more than half of the red-sequence galaxies have early-type morphologies , but the fraction decreases to 30 ％ at z ~ 2-3 . Combining this thesis and other researcher’s work , we suggest that three mechanisms may be responsible for the evolution of the red sequence including galaxy transformation ( the blue cloud turned into the red cloud ) , red merger and aging .