Herschel observations of Cen A: stellar heating of two extragalactic dust clouds Herschel observations of Cen A dust clouds
Herschel observations of Cen A: stellar heating of two extragalactic dust clouds Herschel observations of Cen A dust clouds
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赫歇尔对 Cen A 的观测：两个河外尘埃云的恒星加热 赫歇尔对 Cen A 尘埃云的观测
DOI：
10.1111/j.1365-2966.2011.19819.x
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发表时间：
2012
影响因子：
4.8
通讯作者：
Auld R
中科院分区：
文献类型：
--
作者：
Auld R
我们提出了一个多波长调查的第一个结果，结合赫歇尔，斯皮策，GALEX和澳大利亚望远镜紧凑阵列（ATCA）的观测，一个1°× 1°的领域集中在半人马座A。除了探测活动星系核（AGN）喷流和反喷流的内叶外，我们还发现了两个云，它们在亚毫米波长处明亮，距离Cen A中心约15 kpc，与喷流对齐。在赫歇尔波长的通量测量已被证明是至关重要的约束拟合的光谱能量分布（SED）。这些云很好地拟合了单温度的修正黑体光谱（β= 2），表明我们正在观察岑A外围的两个冷尘埃云。云的温度和质量分别为K，K1，两个云的气尘比都是100。北方尘埃云的测量值与国际标准化组织以前的测量值一致，而南方的尘埃云是一个新的亚毫米探测。这两个尘埃云位于围绕着Cen A的部分H i环的末端，这也是气柱密度达到峰值的地方。赫歇尔的调查包括部分H i环，但我们没有发现任何证据的尘埃排放在任何其他部分的环。假设气尘比在环的其余部分中是相同的，则H i环中的粉尘质量上限与存在的低柱密度粉尘一致，但低于SPIRE检测极限。我们已经讨论了这些云的起源和各种可能的加热机制。观测结果支持这样一种假设，即气体和尘埃曾经是晚型星系的一部分，后来与Cen A合并。充分解释这两个云中观测到的温度的主要加热机制是来自Cen A内演化的恒星群体的加热。
We present the first results of a multiwavelength survey, incorporating Herschel-, Spitzer, GALEX and Australian Telescope Compact Array (ATCA) observations, of a 1°× 1° field centred on Centaurus A. As well as detecting the inner lobes of the active galactic nucleus (AGN) jet and counterjet, we have found two clouds, bright at submillimetre wavelengths,∼ 15 kpc from the centre of Cen A that are co-aligned with the jets. Flux measurements at Herschel wavelengths have proved vital in constraining fits to the spectral energy distributions (SEDs). The clouds are well fitted by a single-temperature, modified blackbody spectrum (β= 2) indicating that we are looking at two cold dust clouds on the outskirts of Cen A. The temperature and masses of the clouds are K, K;, and the gas-dust ratio for both clouds is∼ 100. The measured values for the northern dust cloud are consistent with previous measurements from ISO while the southern cloud is a new submillimetre detection. The two dust clouds are located at the termini of the partial H i ring that surrounds Cen A which is also where the gas column density peaks. The Herschel survey encompasses the partial H i ring yet we find no evidence of dust emission in any other part of the ring. Assuming that the gas–dust ratio is the same in the rest of the ring, dust mass upper limits in the H i ring are consistent with low column density dust being present but falling below the SPIRE detection limit. We have discussed the origin of these clouds and various possible heating mechanisms. The observations favour a scenario in which the gas and dust were once part of a late-type galaxy, which has since merged with Cen A. The dominant heating mechanism which adequately explains the observed temperatures in both clouds is heating from the evolved stellar population within Cen A.