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arXiv 1209.2707astro-ph.CO
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来自GOODS-Herschel巡天的z ~ 2尘埃星系中大范围UV遮蔽的证据

Evidence for a wide range of UV obscuration in z ~ 2 dusty galaxies from the GOODS-Herschel survey

Kyle Penner, Mark Dickinson, Alexandra Pope, Arjun Dey, Benjamin Magnelli, Maurilio Pannella, Bruno Altieri, Herve Aussel, Veronique Buat, Shane Bussmann, Vassi… 展开作者

Kyle Penner, Mark Dickinson, Alexandra Pope, Arjun Dey, Benjamin Magnelli, Maurilio Pannella, Bruno Altieri, Herve Aussel, Veronique Buat, Shane Bussmann, Vassilis Charmandaris, Daniela Coia, Emanuele Daddi, Helmut Dannerbauer, David Elbaz, Ho Seong Hwang, Jeyhan Kartaltepe, Lihwai Lin, Georgios Magdis, Glenn Morrison, Paola Popesso, Douglas Scott, Ivan Valtchanov

摘要:

z ~ 2的尘埃星系在静止帧中红外(8 μ m)和紫外波长之间的相对亮度范围很广。我们试图确定负责这种多样性的物理机制。尘埃遮蔽星系(Dust-obscured galaxies,DOG)的静止坐标系中红外线与紫外线的通量密度比大于1000,可能在中红外线处异常明亮,可能是由于活动星系核和/或多环芳烃的突出发射,或者在紫外线处异常暗淡。我们利用GOODS-Herschel巡天的远红外数据表明,与其他具有类似红外(8- 1000 μ m)光度的尘埃星系相比,大多数10^12 L_Sun < L_IR < 10^13 L_Sun的DOG在中红外并不异常明亮。我们观察到这些星系的中值红外到紫外线光度比和中值紫外线连续幂律指数之间的关系,我们发现,只有24%有特定的恒星形成率,这表明紧凑的恒星形成区域的主导地位。这种间接证据支持的想法,在这些星系的紫外线和红外线发射区域是空间重合的,这意味着异常的紫外线昏暗的DOG和尘埃遮蔽之间的连接。我们的结论是,在静止帧中红外线,紫外线通量密度比跨越尘埃星系在z ~ 2的范围是由于不同数量的紫外线遮蔽。在这些红外光度的星系中,DOG是最模糊的。我们将紫外线遮蔽的差异归因于:1)尘埃和大质量恒星空间分布之间的对齐程度差异,或2)总尘埃含量的差异。

英文摘要:

Dusty galaxies at z ~ 2 span a wide range of relative brightness between rest-frame mid-infrared (8um) and ultraviolet wavelengths. We attempt to determine the physical mechanism responsible for this diversity. Dust-obscured galaxies (DOGs), which have rest-frame mid-IR to UV flux density ratios > 1000, might be abnormally bright in the mid-IR, perhaps due to prominent AGN and/or PAH emission, or abnormally faint in the UV. We use far-infrared data from the GOODS-Herschel survey to show that most DOGs with 10^12 L_Sun < L_IR < 10^13 L_Sun are not abnormally bright in the mid-IR when compared to other dusty galaxies with similar IR (8--1000um) luminosities. We observe a relation between the median IR to UV luminosity ratios and the median UV continuum power-law indices for these galaxies, and we find that only 24% have specific star formation rates which indicate the dominance of compact star-forming regions. This circumstantial evidence supports the idea that the UV- and IR-emitting regions in these galaxies are spatially coincident, which implies a connection between the abnormal UV faintness of DOGs and dust obscuration. We conclude that the range in rest-frame mid-IR to UV flux density ratios spanned by dusty galaxies at z ~ 2 is due to differing amounts of UV obscuration. Of galaxies with these IR luminosities, DOGs are the most obscured. We attribute differences in UV obscuration to either: 1) differences in the degree of alignment between the spatial distributions of dust and massive stars, or 2) differences in the total dust content.

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