We present Herschel-PACS spectroscopy of four main-sequence star-forming galaxies at z~1.5. We detect [OI]63micron line emission in BzK-21000 at z=1.5213, and measure a line luminosity, L([OI]63micron) = (3.9+/-0.7)x1.E+9 Lsun. Our PDR modelling of the interstellar medium in BzK-21000 suggests a UV radiation field strength, G~320 G0, and gas density, n~1800 cm-3, consistent with previous LVG modelling of the molecular CO line excitation. The other three targets in our sample are individually undetected in these data, and we perform a spectral stacking analysis which yields a detection of their average emission and an [OI]63micron line luminosity, L([OI]63micron) =(1.1+/-0.2)x1E+9 Lsun. We find that the implied luminosity ratio, L([OI]63micron)/L(IR), of the undetected BzK-selected star-forming galaxies broadly agrees with that of low-redshift star-forming galaxies, while BzK-21000 has a similar ratio to that of a dusty star-forming galaxy at z~6. The high [OI]63micron line luminosities observed in BzK-21000 and the $z \sim 1 -3$ dusty and submm luminous star-forming galaxies may be associated with extended reservoirs of low density, cool neutral gas.

中文翻译：

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[OI]63 μm 线发射在 z ∼ 1.5 主序星系中的观测

我们展示了 z~1.5 处四个主序星形成星系的赫歇尔-PACS 光谱。我们在 z=1.5213 处检测到 BzK-21000 中的 [OI]63 微米线发射，并测量线光度 L([OI]63 微米) = (3.9+/-0.7)x1.E+9 Lsun。我们对 BzK-21000 中星际介质的 PDR 建模表明，紫外线辐射场强 G~320 G0 和气体密度 n~1800 cm-3，与之前对分子 CO 线激发的 LVG 建模一致。我们样本中的其他三个目标在这些数据中均未检测到，我们进行了光谱叠加分析，检测了它们的平均发射和 [OI]63 微米线光度，L([OI]63 微米) =(1.1+/ -0.2)x1E+9 Lsun。我们发现隐含的光度比，L([OI]63micron)/L(IR)，未探测到的 BzK 选择的恒星形成星系的比例与低红移恒星形成星系的比例大致相同，而 BzK-21000 与 z~6 处的尘埃恒星形成星系的比例相似。在 BzK-21000 和 $z \sim 1 -3$ 尘埃和亚毫米发光恒星形成星系中观察到的高 [OI]63 微米线光度可能与低密度、冷中性气体的扩展储层有关。