MOLECULAR CLOUD-SCALE STAR FORMATION IN NGC 300
MOLECULAR CLOUD-SCALE STAR FORMATION IN NGC 300
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NGC 300 中的分子云级恒星形成
DOI：
10.1088/0004-637x/789/1/81
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
H. Bouy
中科院分区：
文献类型：
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作者：
C. Faesi;C. Lada;J. Forbrich;K. Menten;H. Bouy
我们给出了在附近的螺旋星系NGC300中对76个H II区的全星系分子气体和恒星形成的研究结果。我们利用阿塔卡马探路者实验望远镜的定点CO(J=2-1)观测，在250pC尺度上测量了分子气体。我们在42个目标中检测到CO，得出的分子气体质量范围从我们的灵敏度极限∼105 M☉到7×105 M☉。我们发现，随着银心距离的增加，CO的探测率明显下降，这主要归因于NGC300中径向金属丰度梯度的降低。在我们的样本中，我们结合了星系演化探测器远紫外线、斯皮策24μm和Hα窄带成像来测量恒星形成活动。我们已经开发了一种新的直接建模方法来计算恒星形成率(SFR)，它利用这些数据和人口合成模型来推导与我们的每个H II区域目标相关的年轻星团的质量和年龄。我们在NGC 300中发现，在250pC尺度下，特征气体耗尽时间为230 Myr，这与银河系巨型分子云得到的结果更相似，而不是整个星系及其千帕秒大小区域得到的更长的(>；2 Gyr)全球耗尽时间。这种差异的部分原因是，我们的研究只考虑了最年轻恒星形成区域内的气体和恒星。我们还注意到NGC300SFR-分子气体质量标度关系中的大散射，这与银河云的结果进一步一致。这种分散很可能代表了巨型分子云物理性质的真正差异，例如稠密气体的分数。
We present the results of a galaxy-wide study of molecular gas and star formation in a sample of 76 H ii regions in the nearby spiral galaxy NGC 300. We have measured the molecular gas at 250 pc scales using pointed CO(J = 2–1) observations with the Atacama Pathfinder Experiment telescope. We detect CO in 42 of our targets, deriving molecular gas masses ranging from our sensitivity limit of ∼105 M☉ to 7 × 105 M☉. We find a clear decline in the CO detection rate with galactocentric distance, which we attribute primarily to the decreasing radial metallicity gradient in NGC 300. We combine Galaxy Evolution Explorer far-ultraviolet, Spitzer 24 μm, and Hα narrowband imaging to measure the star formation activity in our sample. We have developed a new direct modeling approach for computing star formation rates (SFRs) that utilizes these data and population synthesis models to derive the masses and ages of the young stellar clusters associated with each of our H ii region targets. We find a characteristic gas depletion time of 230 Myr at 250 pc scales in NGC 300, more similar to the results obtained for Milky Way giant molecular clouds than the longer (>2 Gyr) global depletion times derived for entire galaxies and kiloparsec-sized regions within them. This difference is partially due to the fact that our study accounts for only the gas and stars within the youngest star-forming regions. We also note a large scatter in the NGC 300 SFR–molecular gas mass scaling relation that is furthermore consistent with the Milky Way cloud results. This scatter likely represents real differences in giant molecular cloud physical properties such as the dense gas fraction.