z ~ 2星系的高采样远红外光谱能量分布：冷星系放大的证据
Well-Sampled Far-Infrared Spectral Energy Distributions of z ~ 2 Galaxies: Evidence for Scaled up Cool Galaxies
摘要：
本文分析了两个z = 2.122和z = 2.024的大质量K-选择星系在24 um、70 um、160 um和250 um、350 um、500 um以及870 um的远红外光谱能量分布。这些观测的大波长范围和光谱红移的可用性使我们能够明确地确定尘埃在~ 300 μ m处的红移热发射峰值。这两个星系的SED与L_IR ~ 10^{11} L_{sun} - 10^{12} L_{sun}的本星系合成模板拟合得相当好，但这两个星系的L_{IR} ~ 10^{13} L_{sun}。这表明这些星系不是本地模板中使用的超LIRGs/ULIRGs的高红移类似物，而是本地ULIRGs/LIRGs的“放大”版本。对于这两个星系，从最佳拟合FIR SED确定的恒星形成率（SFR（L_{IR}））与由尘埃校正的H-α光度确定的SFR一致（SFR（H-alpha））的范围在约2倍以内;然而，当仅使用观测到的24 μ m通量和标准的光度依赖模板方法来估计这些星系的SFR时，（SFR（24 μ m）），它系统地高估了SFR多达6倍。从Kriek et al.（2008）GNIRS样本中抽取的z ~ 2.3的24个K选择星系的更大样本显示了SFR（24 um）和SFR（H-alpha）之间的相同趋势。使用该样本，我们表明，SFR（24微米）和SFR（H-α）是在更好的协议时，SFR（24微米）估计使用本地模板的对数平均值，而不是选择一个单一的亮度相关的模板，因为这包含较低的亮度模板。较低光度模板的SFR之间较好的一致性表明，BLAST检测到的星系的FIR SED可能是典型的z ~ 2的大质量星系，大多数是放大版本的低光度本地星系。
英文摘要：
We present an analysis of the far-infrared (FIR) spectral energy distributions (SEDs) of two massive K-selected galaxies at z = 2.122 and z = 2.024 detected at 24um, 70um, 160um by Spitzer, 250um, 350um, 500um by BLAST, and 870um by APEX. The large wavelength range of these observations and the availability of spectroscopic redshifts allow us to unambiguously identify the peak of the redshifted thermal emission from dust at ~ 300um. The SEDs of both galaxies are reasonably well fit by synthetic templates of local galaxies with L_IR ~ 10^{11} L_{sun} -- 10^{12} L_{sun} yet both galaxies have L_{IR} ~ 10^{13} L_{sun}. This suggests that these galaxies are not high redshift analogues of the Hyper-LIRGs/ULIRGs used in local templates, but are instead "scaled up" versions of local ULIRGs/LIRGs. For both galaxies the star formation rate determined from the best-fit FIR SEDs (SFR(L_{IR})) agrees with the SFR determined from the dust corrected H-alpha luminosity (SFR(H-alpha)) to within a factor of ~ 2; however, when the SFR of these galaxies is estimated using only the observed 24um flux and the standard luminosity-dependent template method (SFR(24um)), it systematically overestimates the SFR by as much as a factor of 6. A larger sample of 24 K-selected galaxies at z ~ 2.3 drawn from the Kriek et al. (2008) GNIRS sample shows the same trend between SFR(24um) and SFR(H-alpha). Using that sample we show that SFR(24um) and SFR(H-alpha) are in better agreement when SFR(24um) is estimated using the log average of local templates rather than selecting a single luminosity-dependent template, because this incorporates lower luminosity templates. The better agreement between SFRs from lower luminosity templates suggests that the FIR SEDs of the BLAST-detected galaxies may be typical for massive galaxies at z ~ 2, and that the majority are scaled up versions of lower luminosity local galaxies.
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