The Age Dependence of Mid-infrared Emission around Young Star Clusters
The Age Dependence of Mid-infrared Emission around Young Star Clusters
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DOI：
10.3847/1538-4357/ab9106
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发表时间：
2020-05
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通讯作者：
Zesen Lin;D. Calzetti;X. Kong;A. Adamo;M. Cignoni;D. Cook;Daniel A. Dale;K. Grasha;E. Grebel;M. Messa;E. Sacchi;Linda J. Smith
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作者：
Zesen Lin;D. Calzetti;X. Kong;A. Adamo;M. Cignoni;D. Cook;Daniel A. Dale;K. Grasha;E. Grebel;M. Messa;E. Sacchi;Linda J. Smith
利用哈勃空间望远镜Legacy河外紫外巡天（LEGUS）的星星星表和斯皮策空间望远镜IRAC相机拍摄的5个星系的8 μm图像，研究了8 μm尘埃光度与恒星形成区30-50 pc尺度上恒星年龄的关系。我们构造了一个由97个区域组成的样本，每个区域都集中在8 μm发射的局部峰值上，每个区域都包含一个或多个来自LEGUS星表的年轻星星团候选者。我们发现，质量标准化的尘埃8 μm光度与年龄小于1 Gyr的星团之间存在紧密的相关性，皮尔逊相关系数r = −0.84 ± 0.05; 8 μm光度随着恒星年龄的增加而减小。简单的假设结合恒星和尘埃排放模型再现了观察到的趋势。我们还探讨了如何分散所观察到的趋势取决于假设恒星金属丰度，多环芳烃（PAH）丰度，恒星光被尘埃吸收的分数，瞬时与连续星星形成模型。我们发现恒星金属丰度的变化对散射的影响很小，而PAH丰度和尘埃吸收光的分数包含了整个数据范围。我们还发现，这种趋势是更好地解释连续星星形成，而不是瞬时爆发模型。我们将这一结果归因于在许多地区存在多个不同年龄的星星团。提供了作为年龄函数的仅含尘8 μm排放的上限。
Using the star cluster catalogs from the Hubble Space Telescope program Legacy Extragalactic UV survey (LEGUS) and 8 μm images from the IRAC camera on the Spitzer Space Telescope for five galaxies within 5 Mpc, we investigate how the 8 μm dust luminosity correlates with the stellar age on the 30–50 pc scale of star-forming regions. We construct a sample of 97 regions centered at local peaks of 8 μm emission, each containing one or more young star cluster candidates from the LEGUS catalogs. We find a tight anticorrelation with a Pearson correlation coefficient of r = −0.84 ± 0.05 between the mass-normalized dust-only 8 μm luminosity and the age of stellar clusters younger than 1 Gyr; the 8 μm luminosity decreases with increasing age of the stellar population. Simple assumptions on a combination of stellar and dust emission models reproduce the observed trend. We also explore how the scatter of the observed trend depends on assumptions of stellar metallicity, polycyclic aromatic hydrocarbon (PAH) abundance, fraction of stellar light absorbed by dust, and instantaneous versus continuous star formation models. We find that variations in stellar metallicity have little effect on the scatter, while PAH abundance and the fraction of dust-absorbed light bracket the full range of the data. We also find that the trend is better explained by continuous star formation, rather than instantaneous burst models. We ascribe this result to the presence of multiple star clusters with different ages in many of the regions. Upper limits of the dust-only 8 μm emission as a function of age are provided.