z~2 DOG和SMG的恒星形成历史
The Star-Formation Histories of z~2 DOGs and SMGs
摘要：
斯皮策太空望远镜发现了一群z ~ 2的超亮红外星系，它们可能在大质量星系的演化中起着重要作用。我们测量了斯皮策选择的两个ULIRG群体的恒星质量，这两个群体都具有极红的R-[24]颜色（尘埃遮蔽星系，或DOG），并将我们的结果与亚毫米选择星系（SMG）进行比较。一组39个DOG在静止坐标系1.6 μ m处的中红外光谱能量分布（SED）中有一个局部最大值，与恒星辐射有关（“凸块DOG”），而另一组51个DOG的中红外光谱能量分布（SED）中有一个幂律占主导地位的中红外光谱能量分布，其光谱特征是典型的模糊活动星系核（“幂律DOG”）。我们使用恒星星族合成模型适用于自洽宽带测光在休息帧的紫外线，光学和近红外的这些人口和测试各种恒星星族合成代码，恒星形成历史（SFHS），和初始质量函数（IMF）。假设一个简单的恒星星族SFH和一个Chabrier IMF，我们发现SMG、凸形DOG和幂律DOG的中值和内四分位质量分别为log（M */M太阳）= 10.42 -0.36^+0.42，10.62 -0.32^+0.36和10.71 -0.34^+0.40。实施更复杂的SFH与多个年龄组成部分增加这些质量估计高达0.5 dex。我们对恒星质量的估计与z~2超高速红外暴起源的物理机制是一致的，这导致了给定恒星质量下的高恒星形成率。这种机制通常是由两个富含气体的系统的大合并驱动的，而不是气体和小卫星的平稳吸积。
英文摘要：
The Spitzer Space Telescope has identified a population of ultra-luminous infrared galaxies (ULIRGs) at z ~ 2 that may play an important role in the evolution of massive galaxies. We measure the stellar masses of two populations of Spitzer-selected ULIRGs, both of which have extremely red R-[24] colors (dust-obscured galaxies, or DOGs) and compare our results with sub-millimeter selected galaxies (SMGs). One set of 39 DOGs has a local maximum in their mid-IR spectral energy distribution (SED) at rest-frame 1.6um associated with stellar emission ("bump DOGs"), while the other set of 51 DOGs has a power-law dominated mid-IR SED with spectral features typical of obscured AGN ("power-law DOGs"). We use stellar population synthesis models applied self-consistently to broad-band photometry in the rest-frame ultra-violet, optical, and near-infrared of each of these populations and test a variety of stellar population synthesis codes, star-formation histories (SFHs), and initial mass functions (IMFs). Assuming a simple stellar population SFH and a Chabrier IMF, we find that the median and inner quartile stellar masses of SMGs, bump DOGs and power-law DOGs are given by log(M_*/M_sun) = 10.42_-0.36^+0.42, 10.62_-0.32^+0.36, and 10.71_-0.34^+0.40, respectively. Implementing more complicated SFHs with multiple age components increases these mass estimates by up to 0.5 dex. Our stellar mass estimates are consistent with physical mechanisms for the origin of z~2 ULIRGs that result in high star-formation rates for a given stellar mass. Such mechanisms are usually driven by a major merger of two gas-rich systems, rather than smooth accretion of gas and small satellites.
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