運用模擬資料來探討觀測誤差對星系環境與星系特性研究的影響

Abstract

現今已經有許多種測量星系環境的方法已經被提出來,並且被廣泛 地運用在各種星系形成與演化的研究上面•一般來說,天文觀測的數 據資料有兩大類: 精確度高但數量稀少的光譜類觀測資料以及精確度低但是數量豐富的光度觀測資料•而這些定義星系環境的方式大多被運用在精確度較高的光譜星系觀測資料上面•針對觀測誤差較大的光度星系觀測資料,它們的可用性是需要被探討的•在這個研究中,我們 研究二維的投影星系環境如何被觀測誤差所影響•以及探討二維投影 環境是否能跟真實世界的星系環境有相當程度的相依性•我們運用模 擬的資料來探討他們的相依性•而為了要讓二維的投影環境的還原成 真實世界中的星系環境,我們設計了一個最佳化處理模式能夠找到最 好量測二維星系參數的方式•這組最好的參數能夠讓二維星系環境跟 真實星系環境有最高的相依性•我們也藉由這個最佳化處理過程•來 探討這些星系環境與星系顏色的關係•我們的結果顯示,即便是在觀 測誤差大於 0.06 的情況下,我們仍然可以看見投影星系環境能跟星系 顏色有一定程度的相依性•我們最後也探討了這個最佳化處理過程在 泛星計畫上的運用•

Many estimators of environment have been proposed and tested to quantify the environmental effect successfully. While those environmental estimators in general work well with spectroscopic redshift (spectral-z hereafter) samples, their applications to photometric redshift (photo-z hereafter) surveys is uncertain. In this work, we study how the 2D projected galaxy environments are affected by photo-z error and how the 2D projected galaxy environments are correlated with 3D real-space environment. We use the Durham mock catalog built on Millennium Simulation to study their correlation. To recover the 3D real-space galaxy environments from 2D projected environments, we construct the Optimized Scheme which can probe the best parameters of measurement to measure the 2D projected environments that yield the best correlation with 3D real-space environments. We also study the correlation between the red fraction and galaxy environment by using the results from optimized schemes. Our results show that the color-density relation can still be revealed in photo-z samples with photo-z error up to 0.06(1+z). We also discuss its application to the Pan-STARRS Medium Deep survey, one of the largest on-going deep imaging surveys.