z ~ 2星系的GMASS超深光谱。IV。尘埃种群的多样性
GMASS ultradeep spectroscopy of galaxies at z ~ 2. IV. The variety of dust populations
摘要：
尘埃在静止坐标系紫外波段的衰减特性是从GMASS巡天的78个星系在1<z<2.5的高质量FORS 2光谱中推断出来的。这些天体补充了先前调查的108个具有类似红移的紫外发光星系的样本，这些样本选自FDF光谱调查，K20调查和GDDS。UV消光曲线的形状受到静止帧UV连续体的参数化描述的约束。UV凸点的特征还在于拟合洛伦兹样轮廓。光谱在至少30%的情况下表现出显著的2175 A特征。如果衰减主要是由从星系主体通过超级风喷出的尘埃，紫外线消光曲线之间的SMC和LMC的样本星系。如果更多的尘埃驻留在银道面或尘埃衰减取决于恒星的年龄，则与SMC不同的消光曲线的星系的比例增加。平均而言，显现的紫外线隆起的宽度约为LMC和银河系典型值的60%。这表明在接近30 Dor的LMC 2超壳层中存在类似的尘埃。在1<z<2.5处的紫外线隆起的载流子的存在证明了AGB恒星的外流是丰富的。与它们较高的SFR相一致，具有明显紫外线凸起的GMASS星系在静止帧8 μ m处更明亮，其中发射主要是多环芳烃（也是AGB星的产物）。此外，它们表现出更强的紫外线吸收特征，大多数是星际起源，这表明整体上更进化的恒星星族。我们的结论是，在1<z<2.5的最演化的恒星形成系统中，小尺寸尘埃成分的多样化已经开始。
英文摘要：
The properties of dust attenuation at rest-frame UV wavelengths are inferred from very high-quality FORS2 spectra of 78 galaxies from the GMASS survey at 1<z<2.5. These objects complement a previously investigated sample of 108 UV-luminous galaxies at similar redshifts, selected from the FDF spectroscopic survey, the K20 survey, and the GDDS. The shape of the UV extinction curve is constrained by a parametric description of the rest-frame UV continuum. The UV bump is further characterised by fitting Lorentzian-like profiles. Spectra exhibit a significant 2175A feature in at least 30% of the cases. If attenuation is dominated by dust ejected from the galaxy main body via superwinds, UV extinction curves in-between those of the SMC and LMC characterise the sample galaxies. The fraction of galaxies with extinction curves differing from the SMC one increases, if more dust resides in the galactic plane or dust attenuation depends on stellar age. On average, the width of the manifested UV bumps is about 60% of the values typical of the LMC and Milky Way. This suggests the presence of dust similar to that found in the LMC2 supershell close to 30Dor. The presence of the carriers of the UV bump at 1<z<2.5 argues for outflows from AGB stars being copious then. Consistent with their higher SFRs, the GMASS galaxies with a manifested UV bump are more luminous at rest-frame 8mum, where the emission is dominated by PAHs (also products of AGB stars). In addition, they exhibit stronger UV absorption features, mostly of interstellar origin, which indicates overall more evolved stellar populations. We conclude that diversification of the small-size dust component has already started in the most evolved star-forming systems at 1<z<2.5.
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