A Study of Absorption Molecular Clouds in the Centaurus A using ALMA Data

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/83197

Title:	A Study of Absorption Molecular Clouds in the Centaurus A using ALMA Data
Authors:	許棨甯;Hsu, Qi–Ning
Contributors:	天文研究所
Keywords:	半人馬座Ａ;分子雲;星系;吸收譜線;Centaurus A;Molecular cloud;Galaxy;Absorption line
Date:	2020-07-28
Issue Date:	2020-09-02 15:07:14 (UTC+8)
Publisher:	國立中央大學
Abstract:	星際介質 (ISM)是一個包含了星際間的氣體、塵埃、和磁場等成份的混合體。這些物質普遍被認為在星系的演化當中扮演了重要的角色。在星際介質的組成當中有一部分是所謂的分子雲，這些分子雲不僅僅是形成恆星所需要的重要成分，同時也是位於星系中心的大質量黑洞的燃料來源。當分子雲失去其角動量的時候，這些分子雲就有機會掉進大質量黑洞內並且點燃大質量黑洞的活躍性。但是到目前為止這些靠近黑洞的分子雲的物理性質都還在探討中。在本篇研究當中，我們以離太陽最近的透鏡星系「半人馬座A (Centaurus A)」作為研究對象。在早期的研究中發現在靠近這個星系的中心位置上有非常明顯的分子吸收光譜，並且依照速度的大小，將這些譜線分為低速群和高速群兩大類。然而造成這些吸收線的分子雲的來源及物理特性都尚未有定論。所以我們利用阿塔卡瑪大型毫米及次毫米波陣列 (ALMA)所得到的觀測資料來分析CO(J=1–0)、CO(J=2–1)、CO(J=3–2)、以及HCO+(J=1–0)這些分子的吸收譜線，並探討這些吸收分子雲的物理特性及可能的起源。;We analyze the molecular absorption features toward the nucleus of the nearest lenticular galaxy Centaurus A (NGC 5128) by using the ALMA (Atacama Large Millimeter/submillimeter Array) archival data. There is no consensus on the origin of these absorption lines. We identify eighteen absorption line components and determine the physical conditions of these line components in the CO(J=1–0), CO(J=2–1), CO(J=3–2), and HCO+(J=1–0) spectra. There are two major groups of these absorption line components referred to as the low velocity complex (LVC) and high velocity complex (HVC). Our results indicate that the HVC clouds are consisting of small molecular clouds and are more excited comparing with the LVC clouds. These HVC clouds might be the molecular clouds that are falling into the central active galactic nucleus (AGN) of Centaurus A and the properties of the HVC clouds are significantly affected by the AGN.
Appears in Collections:	[Graduate Institute of Astronomy] Electronic Thesis & Dissertation

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