THE INFLUENCE OF FAR-ULTRAVIOLET RADIATION ON THE PROPERTIES OF MOLECULAR CLOUDS IN THE 30 DOR REGION OF THE LARGE MAGELLANIC CLOUD
THE INFLUENCE OF FAR-ULTRAVIOLET RADIATION ON THE PROPERTIES OF MOLECULAR CLOUDS IN THE 30 DOR REGION OF THE LARGE MAGELLANIC CLOUD
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DOI：
10.1088/0004-637x/703/1/736
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发表时间：
2009-07
期刊：
影响因子：
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通讯作者：
Jorge L. Pineda;J. Ott;U. Klein;Tony Wong;E. Muller;A. Hughes
中科院分区：
文献类型：
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作者：
Jorge L. Pineda;J. Ott;U. Klein;Tony Wong;E. Muller;A. Hughes
我们展示了用 22 m ATNF Mopra 望远镜获得的大麦哲伦星云 (LMC) 中突出分子脊的完整 12CO J = 1 → 0 图。该区域从剑鱼座 30 处向南延伸约 2°（或 1.7 kpc），剑鱼座是本星系群中最活跃的恒星形成区域。该分子脊的位置是独特的，因为它使我们能够研究分子气体的特性作为低金属丰度环境中周围辐射场的函数。我们发现分子脊内的CO发射团块的物理性质不随远紫外辐射场的强度而变化。由于团块的峰值 CO 亮度与辐射场强度没有相关性，因此观察到的沿脊线的 CO 到 H2 转换因子的恒定值似乎需要分子气体的动力学温度的增加，而这可以通过 CO 发射的角填充因子的降低来抵消。我们发现，分子脊和外银河系中CO到H2转换因子之间的差异比之前关于CO排放的研究报告的差异要小：对我们对LMC分子脊的CO观测和Dame等人的外星系巡天CO数据应用相同的云识别和分析方法，我们发现分子脊中CO到H2转换因子的平均值为XCO≃（3.9±2.5）×1020 cm−2 (K km s−1)−1，大约是我们为外星系云确定的值的两倍。分子脊中二氧化碳团块性质之间的质谱和比例关系与为银河分子云建立的那些类似，但不相同。
We present a complete 12CO J = 1 → 0 map of the prominent molecular ridge in the Large Magellanic Cloud (LMC) obtained with the 22 m ATNF Mopra Telescope. The region stretches southward by ∼2° (or 1.7 kpc) from 30 Doradus, the most vigorous star-forming region in the Local Group. The location of this molecular ridge is unique insofar as it allows us to study the properties of molecular gas as a function of the ambient radiation field in a low-metallicity environment. We find that the physical properties of CO-emitting clumps within the molecular ridge do not vary with the strength of the far-ultraviolet radiation field. Since the peak CO brightness of the clumps shows no correlation with the radiation field strength, the observed constant value for CO-to-H2 conversion factor along the ridge seems to require an increase in the kinetic temperature of the molecular gas that is offset by a decrease in the angular filling factor of the CO emission. We find that the difference between the CO-to-H2 conversion factor in the molecular ridge and the outer Milky Way is smaller than has been reported by previous studies of the CO emission: applying the same cloud identification and analysis methods to our CO observations of the LMC molecular ridge and CO data from the outer Galaxy survey by Dame et al., we find that the average CO-to-H2 conversion factor in the molecular ridge is XCO ≃ (3.9 ± 2.5) × 1020 cm−2 (K km s−1)−1, approximately twice the value that we determine for the outer Galaxy clouds. The mass spectrum and the scaling relations between the properties of the CO clumps in the molecular ridge are similar, but not identical, to those that have been established for Galactic molecular clouds.