A Mid-Infrared Spectroscopic Study of Submillimeter Galaxies: Luminous Starbursts at High Redshift
A Mid-Infrared Spectroscopic Study of Submillimeter Galaxies: Luminous Starbursts at High Redshift
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DOI：
10.1086/513306
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发表时间：
2007-01
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影响因子：
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通讯作者：
E. Valiante;D. Lutz;E. Sturm;R. Genzel;L. Tacconi;M. Lehnert;Andrew J. Baker
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文献类型：
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作者：
E. Valiante;D. Lutz;E. Sturm;R. Genzel;L. Tacconi;M. Lehnert;Andrew J. Baker
我们给出了用斯皮策太空望远镜上的红外光谱仪(IRS)获得的13个亚毫米星系样本的静止框架中红外光谱。样本只包括来自空白区域的明亮物体和具有准确干涉位置的集群透镜辅助测量。我们发现，大多数光谱都可以通过恒星爆发模板或PAH发射特征和弱中红外连续统的叠加来很好地拟合，后者是活动星系核(包括康普顿厚的活动星系核)的示踪剂。我们获得了用红外光谱探测到的所有九个源的中红外光谱红移。其中三人的红移此前是未知的。假设四个红外探测器都处于高红移，则红移分布的中值为z~2.8。仅IRS探测的中位数就是z~2.7。将未探测到的红外探测器置于类似的红移将需要比在本地ULIRG中看到的更大的静止帧中红外遮挡。静止框架的中红外光谱和中远红外光谱能量分布与本地区的超高亮度红外星系一致，但在光度上进一步放大。中红外光谱支持这样的假设，即亚毫米星系是极端恒星形成的地点，而不是被X射线遮挡的活动星系核，并且代表了大质量星系形成的关键阶段。
We present rest-frame mid-infrared spectroscopy of a sample of 13 submillimeter galaxies, obtained using the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. The sample includes exclusively bright objects from blank fields and cluster lens-assisted surveys that have accurate interferometric positions. We find that the majority of spectra are well fitted by a starburst template or by the superposition of PAH emission features and a weak mid-infrared continuum, the latter a tracer of active galactic nuclei (AGNs; including Compton-thick ones). We obtain mid-infrared spectroscopic redshifts for all nine sources detected with IRS. For three of them the redshifts were previously unknown. The median value of the redshift distribution is z ~ 2.8 if we assume that the four IRS nondetections are at high redshift. The median for the IRS detections alone is z ~ 2.7. Placing the IRS nondetections at similar redshift would require rest-frame mid-IR obscuration larger than is seen in local ULIRGs. The rest-frame mid-infrared spectra and mid- to far-infrared spectral energy distributions are consistent with those of local ultraluminous infrared galaxies but scaled up further in luminosity. The mid-infrared spectra support the scenario that submillimeter galaxies are sites of extreme star formation, rather than X-ray-obscured AGNs, and represent a critical phase in the formation of massive galaxies.