Blair Samantha K, Magnani Loris, Brand Jan, Wouterloot Jan G A
Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602, USA.
Astrobiology. 2008 Feb;8(1):59-73. doi: 10.1089/ast.2007.0171.
We present results from an initial survey of the 2(12)-1(11) transition of formaldehyde (H2CO) at 140.8 GHz in giant molecular clouds in the far outer Galaxy (RG >or= 16 kpc). Formaldehyde is a key prebiotic molecule that likely plays an important role in the development of amino acids. Determining the outermost extent of the H2CO distribution can constrain the outer limit of the Galactic Habitable Zone, the region where conditions for the formation of life are thought to be most favorable. We surveyed 69 molecular clouds in the outer Galaxy, ranging from 12 to 23.5 kpc in galactocentric radius. Formaldehyde emission at 140.8 GHz was detected in 65% of the clouds. The H2CO spectral line was detected in 26 of the clouds with RG > 16 kpc (detection rate of 59%), including 6 clouds with RG > 20 kpc (detection rate of 55%). Formaldehyde is readily found in the far outer Galaxy-even beyond the edge of the old stellar disk. Determining the relatively widespread distribution of H2CO in the far outer Galaxy is a first step in establishing how favorable an environment this vast region of the Galaxy may be toward the formation of life.
我们展示了对银河系最外层（河外半径RG≥16千秒差距）巨分子云中甲醛（H₂CO）在140.8吉赫兹处2(12)-1(11)跃迁的初步调查结果。甲醛是一种关键的益生元分子，可能在氨基酸的形成过程中发挥重要作用。确定H₂CO分布的最外层范围可以限制银河系宜居带的外部界限，即被认为生命形成条件最为有利的区域。我们对银河系外层的69个分子云进行了调查，这些分子云的银心半径在12至23.5千秒差距之间。在65%的分子云中检测到了140.8吉赫兹的甲醛发射。在河外半径RG>16千秒差距的26个分子云中检测到了H₂CO谱线（检测率为59%），其中包括6个河外半径RG>20千秒差距的分子云（检测率为55%）。即使在古老恒星盘的边缘之外，在银河系最外层也很容易发现甲醛。确定H₂CO在银河系最外层相对广泛的分布是了解银河系这一广阔区域对生命形成的环境有多有利的第一步。
