z=1.5圆盘盖层中的高含气率和扩展气藏
Very High Gas Fractions and Extended Gas Reservoirs in z=1.5 Disk Galaxies
摘要：
基于IRAM PdBI获得的多配置CO[2-1]观测结果，我们提出了在z~1.5的正常近红外选择（BzK）星系中非常高的气体分数和扩展分子气体库的证据。观测到的六个星系中有六个被安全地探测到。高分辨率的观测解决了其中四个CO排放，这意味着6-11千秒差距的顺序大小，并建议旋转的存在。UV形态与团簇、不稳定盘一致，并且UV尺寸与CO尺寸一致。恒星的形成效率是均匀的低，类似于局部螺旋-产生的气体耗尽时间约为0.5 Gyr，远高于在高z亚毫米星系和类星体中看到的。CO的光度可以预测到0.15德克斯从恒星形成率和恒星质量，这意味着这些数量的气体质量的紧密相关性。我们利用星团盘星系的动力学模型来推导星系的动力学质量。这些模型能够再现CO发射的特殊谱线形状。在考虑了恒星和暗物质的质量后，我们得出气体的质量为0.4- 1.2 × 10 ^11 Msun。转换因子非常高：α_CO=3.6+-0.8，与银河系一致，但比本地超亮红外星系高4倍。在星系的半光半径内，气体占了重子的50-65%。我们正在目睹z~1.5的真正气体主导的星系，这一发现解释了z>1星系观察到的高特异性SFR。BzK星系可以被看作是局部盘星系的放大版本，低效率的恒星形成发生在扩展的低激发气体盘中。它们明显不同于局部ULIRGs和高Z亚毫米星系，后者具有更多的激发和致密气体。
英文摘要：
We present evidence for very high gas fractions and extended molecular gas reservoirs in normal, near-infrared selected (BzK) galaxies at z~1.5, based on multi-configuration CO[2-1] observations obtained at the IRAM PdBI. Six of the six galaxies observed were securely detected. High resolution observations resolve the CO emission in four of them, implying sizes of order of 6-11 kpc and suggesting the presence of rotation. The UV morphologies are consistent with clumpy, unstable disks, and the UV sizes are consistent with the CO sizes. The star formation efficiencies are homogeneously low and similar to local spirals - the resulting gas depletion times are ~0.5 Gyr, much higher than what is seen in high-z submm galaxies and quasars. The CO luminosities can be predicted to within 0.15 dex from the star formation rates and stellar masses, implying a tight correlation of the gas mass with these quantities. We use dynamical models of clumpy disk galaxies to derive dynamical masses. These models are able to reproduce the peculiar spectral line shapes of the CO emission. After accounting for the stellar and dark matter masses we derive gas masses of 0.4-1.2x10^11 Msun. The conversion factor is very high: alpha_CO=3.6+-0.8, consistent with the Galaxy but four times higher than that of local ultra-luminous IR galaxies. The gas accounts for an impressive 50-65% of the baryons within the galaxies' half light radii. We are witnessing truly gas-dominated galaxies at z~1.5, a finding that explains the high specific SFRs observed for z>1 galaxies. The BzK galaxies can be viewed as scaled-up versions of local disk galaxies, with low efficiency star formation taking place inside extended, low excitation gas disks. They are markedly different than local ULIRGs and high-z submm galaxies, which have more excited and compact gas.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
