1 < z < 3恒星形成星系的LBT和Spitzer光谱：消光和恒星形成速率指示
LBT and Spitzer Spectroscopy of Star-Forming Galaxies at 1 < z < 3: Extinction and Star Formation Rate Indicators
摘要：
利用大双筒望远镜上的LUCIFER仪器和斯皮策望远镜上的红外摄谱仪对4个红移为1 < z < 3的引力透镜红外发光恒星形成星系进行了静止坐标系光学和近中红外波段的光谱观测。该样本被选择来代表纯粹的，活跃的恒星形成系统，没有活动星系核。大的透镜放大率导致高信噪比光谱，可以探测微弱的IR复合线，包括高红移的Pa-α和Br-α。样本被三个透镜星系与类似的套件未发表的数据和观察文献，导致最终的样本七个星系。我们使用红外复合线结合H-α观测探测这些系统的消光，Av，以及测试恒星形成率（SFR）指标对SFR测量拟合光谱能量分布远红外测光。我们的星系占据的Av范围从~0到5.9等，大于以前已知的类似范围的红外光度在这些红移。因此，即使在z ~ 2处对SFR的估计也必须仔细计算红外亮度最高的星系中的灭绝。我们还测量消光比较SFR估计从光发射线与远红外测量。这两种独立方法的结果的比较表明，在1 < z < 3时，灰尘分布情况多种多样。在没有修正尘埃消光的情况下，H-alpha SFR指标低估了SFR;必要修正的大小取决于红外光度和尘埃分布情况。基于6.2微米PAH发射线光度的单个SFR估计值未显示与消光的系统性差异，尽管观察到相当大的~0.2 dex散射。
英文摘要：
We present spectroscopic observations in the rest-frame optical and near- to mid-infrared wavelengths of four gravitationally lensed infrared (IR) luminous star-forming galaxies at redshift 1 < z < 3 from the LUCIFER instrument on the Large Binocular Telescope and the Infrared Spectrograph on Spitzer. The sample was selected to represent pure, actively star-forming systems, absent of active galactic nuclei. The large lensing magnifications result in high signal-to-noise spectra that can probe faint IR recombination lines, including Pa-alpha and Br-alpha at high redshifts. The sample was augmented by three lensed galaxies with similar suites of unpublished data and observations from the literature, resulting in the final sample of seven galaxies. We use the IR recombination lines in conjunction with H-alpha observations to probe the extinction, Av, of these systems, as well as testing star formation rate (SFR) indicators against the SFR measured by fitting spectral energy distributions to far-IR photometry. Our galaxies occupy a range of Av from ~0 to 5.9 mag, larger than previously known for a similar range of IR luminosities at these redshifts. Thus, estimates of SFR even at z ~ 2 must take careful count of extinction in the most IR luminous galaxies. We also measure extinction by comparing SFR estimates from optical emission lines with those from far-IR measurements. The comparison of results from these two independent methods indicates a large variety of dust distribution scenarios at 1 < z < 3. Without correcting for dust extinction, the H-alpha SFR indicator underestimates the SFR; the size of the necessary correction depends on the IR luminosity and dust distribution scenario. Individual SFR estimates based on the 6.2 micron PAH emission line luminosity do not show a systematic discrepancy with extinction, although a considerable, ~0.2 dex scatter is observed.
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