中心分子區

中心分子區（英語：Central Molecular Zone，CMZ）是銀河系的一個區域，在這個複合巨分子雲中富含約6,000萬太陽質量（M_☉）的氣體^[1]。它位於人馬座，經度在銀河的經度介於1.7°和 -0.7°之間，緯度在 -0.2°和+0.2°之間，橫跨銀河系的中心。

CMZ在氣體密度、溫度和湍流方面與銀河系的其它大體積有很大不同^[2]。它的分子氣體密度比星系盤大幾個數量級。它的氣體溫度通常在50至100 K之間，但特別是在銀河中心附近，可以高達400至600 K。CMZ內譜線寬度的採樣在15至50 km/s的範圍內，而星系盤中的巨分子雲的採樣速度為1至10 km/s。此外，與銀盤相比，CMZ產生的宇宙射線通量更高，還發射出大量的紫外線和X射線輻射^[3]。

CMZ是不對稱的^[4]直徑從大約1600光年到1900光年不等。其最高氣體表面密度位於銀河系動力中心以東正緯度和速度處。對CMZ質量分佈的估計表明，它在正銀河緯度的質量是其負緯度的三倍。除了其內部不對稱性外，CMZ的軌道平面可能相對於整個銀河系平面傾斜約5°^[5]。

CMZ包含各種超新星遺跡和發射星雲^[6]。氣體濃度較高的區域被命名為人馬座D HII、人馬座D SNR、SNR 0.9+0.1、人馬座B1、人馬座B2、SNR 0.3+0.0、人馬座A、SNR 359.1-00.5、 SNR 359.0-00.9、人馬座C、人馬座E，還有被稱為老鼠、蛇和手杖的線狀特徵。在該區域發現的分子包括一氧化碳、甲醇、異氰酸、氰化氫和一氧化矽^[7]。直徑約為0.1至0.65光年的冷塵埃濃度數量至少有數百個，它們可能是未來恆星系統的祖先核心^[8]。

參考資料

^ Harvard-Smithsonian Center for Astrophysics. Cold dust cores in the central zone of the Milky Way. PHYS ORG. Science X. [22 February 2021].
^ Mills2017
^ HSCA-Cold_Dust_Cores
^ Mills, E.A.C. The Milky Way's Central Molecular Zone. May 2017. arXiv:1705.05332  [astro-ph.GA].
^ Tress, Robin G.; et al. Simulations of the Milky Way's central molecular zone - I. Gas dynamics. Monthly Notices of the Royal Astronomical Society (Monthly Notices of the Royal Astronomical Society, Volume 499, Issue 3, pp.4455-4478). October 2020, 499 (3): 4455–4478. arXiv:2004.06724  . doi:10.1093/mnras/staa3120.
^ Nemiroff, R.; Bonnell, J. (編). Our Galaxy's Central Molecular Zone. Astronomy Picture of the Day. NASA. 10 November 2008 [10 October 2012].
^ The Mopra Central Molecular Zone Molecular Line Mapping Survey. [10 October 2012]. （原始內容存檔於19 February 2014）.
^ Hatchfield, H Perry; et al. CMZoom. II. Catalog of Compact Submillimeter Dust Continuum Sources in the Milky Way's Central Molecular Zone. The Astrophysical Journal Supplement Series. November 2020, 251 (1): 14. Bibcode:2020ApJS..251...14H. S2CID 221640775. arXiv:2009.05052  . doi:10.3847/1538-4365/abb610  .

[1] Harvard-Smithsonian Center for Astrophysics. Cold dust cores in the central zone of the Milky Way. PHYS ORG. Science X. [22 February 2021].

[2] Mills2017

[3] HSCA-Cold_Dust_Cores

[4] Mills, E.A.C. The Milky Way's Central Molecular Zone. May 2017. arXiv:1705.05332  [astro-ph.GA].

[5] Tress, Robin G.; et al. Simulations of the Milky Way's central molecular zone - I. Gas dynamics. Monthly Notices of the Royal Astronomical Society (Monthly Notices of the Royal Astronomical Society, Volume 499, Issue 3, pp.4455-4478). October 2020, 499 (3): 4455–4478. arXiv:2004.06724  . doi:10.1093/mnras/staa3120.

[6] Nemiroff, R.; Bonnell, J. (編). Our Galaxy's Central Molecular Zone. Astronomy Picture of the Day. NASA. 10 November 2008 [10 October 2012].

[7] The Mopra Central Molecular Zone Molecular Line Mapping Survey. [10 October 2012]. （原始內容存檔於19 February 2014）.

[8] Hatchfield, H Perry; et al. CMZoom. II. Catalog of Compact Submillimeter Dust Continuum Sources in the Milky Way's Central Molecular Zone. The Astrophysical Journal Supplement Series. November 2020, 251 (1): 14. Bibcode:2020ApJS..251...14H. S2CID 221640775. arXiv:2009.05052  . doi:10.3847/1538-4365/abb610  .

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