系統編號:88NCU00199004 出版年:民89
研究生:陳正元 Jeng-Yuan, Chen
論文名稱: 亮紅外線星系ARP 55的CO(J=2-1)和CO(J=1-0)之譜線研究
指導教授:黃崇源
學位類別:碩士
校院系所名稱:國立中央大學天文研究所
關鍵字:星劇增 一氧化碳
[摘要]
這次我們利用BIMA毫米波陣列，研究ARP 55中分子氣體的動力構造分佈和物理狀態，進而了解一些亮紅外星系的特性。 ARP 55星系的紅外亮度(LIR=1011.70L⊙)比銀河系強了幾十倍， 造成的原因可能是當中的兩星系互相碰撞合併，而產生星劇增的現象而加熱初生恆星週圍的灰塵，發出許多紅外線的熱輻射。恆星的形成和星系中的分子氣體相互有關係，而理論預測當星系碰撞合倂時，分子氣體會向星系中心集中。
這篇論文中包含CO(J=2-1)和CO(J=1-0)的觀測結果，我們發現兩譜線的輻射區域均集中在東側星系中心並且幾乎重疊，但西側星系只有CO(J=1-0)有明顯的訊號。東側的分子雲氣質量(1.74×1010M⊙)比西側高(6.65×109M⊙)，而且兩星系個別的分子雲氣的質量都比銀河系高(3.5×109M⊙)，並且分子氣體都有集中在星系中心的趨勢。
兩譜線指出東側星系的分子雲氣似乎有由上往下的運動，西側星系速度分佈沒有一個整體趨勢。而ARP 55中兩星系的兩譜線強度比各不相同(E~1.89，W~0.46)，代表其物理環境並不相同。推測東側星系分子氣體可能比一般星系溫度高密度大，而西側星系可能和一般星系差不多。由Hα的觀測及20cm無線電連續譜觀測，也都指出東側星系的恆星活動比較強烈。換句話說，星系碰撞合併時，並不是都處在星遽增的狀態下，可能只有一個星系正在進行星遽增活動，而另一個仍保持一般普通星系的狀態。
We use the BIMA radio mm-array to observe the molecular cloud of ARP55, and research the dynamic distribution and physical condition of the cloud. This program would help us to understand the properties of the luminous infrared galaxies more. The infrared luminosity (LIR) of ARP55 is 1011.70L⊙.That is stronger tens times than our galaxy. The high IR maybe cause by two galaxies interaction or merger in ARP55, and then lead the starburst to heat the dust surround the new stars. The dust emits very much thermal radiation in IR. Star formations have the relation with the molecular cloud in the galaxy. When the galaxies interactions or merger, the molecular cloud will concentrate into the center of the galaxy by the theories and observations.
This paper is the observational results for the molecular emission line of CO(J=2-1) and CO(J=1-0).We find that the emission regions of both two line concentrate in the center of the east galaxy and overlap, but the west galaxy only have the obvious signal of the CO(J=1-0) line. The mass of the molecular cloud in the east galaxy(1.74*1010M⊙) is much than the molecular cloud in the west galaxy(6.65*109M⊙). The molecular cloud mass in each galaxy of Arp55(east and west) is much than our galaxy(3.5*109M⊙), and the molecular gas in ARP 55 contracts in the center of each galaxy.
The analysis of the data indicates that the molecular cloud of the east galaxy have up-to-down motions possibly. The west galaxy has a random distribution of velocity. The intensity ratio [I=CO(J=2-1)/CO(J=1-0)] of two emission lines in two galaxies are different(E~1.89，W~0.46). That points out the environments of two galaxies are different. We infer the molecular cloud of east galaxy has higher temperature and density than normal galaxy. The west galaxy is as same as normal galaxy. With the observations of Hα and 20cm radio-continuum, we can indicate the east galaxy is active than normal galaxy. In the other words, when two galaxies merge, not both of them are in the starburst. Maybe one is active in the starburst, and the other remains to be a normal galaxy.