恒星形成还是恒星爆发？紫外线之谜
Star-Forming or Starbursting? The Ultraviolet Conundrum
摘要：
与星暴星系相比，正常的恒星形成星系在固定的红化下显示出更大的尘埃衰减分散度，这是通过对IRX-beta图（IR/UV比“IRX”与UV颜色“beta”）的研究得出的。为了研究这种较大的色散的原因，并试图隔离第二个参数，我们使用了GALEX紫外线，地面光学，斯皮策红外成像的8个附近的星系，并检查了个人的紫外线和24微米选定的恒星形成区域的属性。我们把注意力集中在恒星形成区域，以便分离出比描述整个星系的恒星形成历史更简单的恒星形成历史。我们发现：1）色散与恒星星族的平均年龄无关; 2）一系列尘埃几何形状和尘埃消光曲线是IRX-β图中观测到的色散的最可能原因; 3）至少在星系内的恒星形成区，最近的恒星形成区可能被较老的不相关爆发稀释，4）我们还恢复了一些区域的一般特征，包括灰尘衰减量与金属含量之间的紧密正相关性。虽然将我们的结果推广到整个星系可能不会立即，但在后者的系统中也应该考虑到一系列尘埃消光定律和几何形状的可能性。
英文摘要：
Compared to starburst galaxies, normal star forming galaxies have been shown to display a much larger dispersion of the dust attenuation at fixed reddening through studies of the IRX-beta diagram (the IR/UV ratio "IRX" versus the UV color "beta"). To investigate the causes of this larger dispersion and attempt to isolate second parameters, we have used GALEX UV, ground-based optical, and Spitzer infrared imaging of 8 nearby galaxies, and examined the properties of individual UV and 24 micron selected star forming regions. We concentrated on star-forming regions, in order to isolate simpler star formation histories than those that characterize whole galaxies. We find that 1) the dispersion is not correlated with the mean age of the stellar populations, 2) a range of dust geometries and dust extinction curves are the most likely causes for the observed dispersion in the IRX-beta diagram 3) together with some potential dilution of the most recent star-forming population by older unrelated bursts, at least in the case of star-forming regions within galaxies, 4) we also recover some general characteristics of the regions, including a tight positive correlation between the amount of dust attenuation and the metal content. Although generalizing our results to whole galaxies may not be immediate, the possibility of a range of dust extinction laws and geometries should be accounted for in the latter systems as well.
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