Systematic Difference between Ionized and Molecular Gas Velocity Dispersions in z ∼ 1–2 Disks and Local Analogs
Systematic Difference between Ionized and Molecular Gas Velocity Dispersions in z ∼ 1–2 Disks and Local Analogs
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DOI：
10.3847/1538-4357/abd5b9
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发表时间：
2021-01
期刊：
影响因子：
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通讯作者：
M. Girard;D. Fisher;A. Bolatto;R. Abraham;R. Bassett;K. Glazebrook;R. Herrera-Camus;E. Jiménez;L. Lenkić;D. Obreschkow
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文献类型：
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作者：
M. Girard;D. Fisher;A. Bolatto;R. Abraham;R. Bassett;K. Glazebrook;R. Herrera-Camus;E. Jiménez;L. Lenkić;D. Obreschkow
我们比较了分子和电离气体的速度色散附近的9个湍流盘，类似高红移星系，从Atacama大毫米/亚毫米阵列和GMOS/双子座观测新的Atacama样本。我们结合联合收割机我们的样品与12个星系在z = 0.5-2.5的文献。我们发现，解决的速度色散是系统的低的一个因素2.45 ± 0.38的分子气体相比，电离气体，热加宽后校正。这种偏移在星系盘内是恒定的，表明薄的分子气体盘和厚的电离气体盘共存。这一结果对Toomre Q和星系中的压力有直接影响。用分子气速色散σ 0，mol.发现σ 0，mol随气体分数和星星形成率的增加而增加。我们还得到了随着红移的增加，并表明EAGLE和FIRE模拟整体高估了σ 0，mol在高红移。我们的研究结果表明，在宇宙星星形成的高峰期，使用电离气体作为总气体的代理来比较气体运动学的努力可能会高估星系中的速度色散。当使用分子气体作为示踪剂时，我们的样本与恒定效率的星星形成模型的预测不一致，即使将传输作为湍流源也是如此。具有可变星星形成效率的反馈模型，和/或反馈效率，p */m *，更好地预测我们的观测结果。
We compare the molecular and ionized gas velocity dispersions of nine nearby turbulent disks, analogs to high-redshift galaxies, from the DYNAMO sample using new Atacama Large Millimeter/submillimeter Array and GMOS/Gemini observations. We combine our sample with 12 galaxies at z ∼ 0.5–2.5 from the literature. We find that the resolved velocity dispersion is systematically lower by a factor 2.45 ± 0.38 for the molecular gas compared to the ionized gas, after correcting for thermal broadening. This offset is constant within the galaxy disks and indicates the coexistence of a thin molecular gas disk and a thick ionized one. This result has a direct impact on the Toomre Q and pressure derived in galaxies. We obtain pressures ∼0.22 dex lower on average when using the molecular gas velocity dispersion, σ 0,mol. We find that σ 0,mol increases with gas fraction and star formation rate. We also obtain an increase with redshift and show that the EAGLE and FIRE simulations overall overestimate σ 0,mol at high redshift. Our results suggest that efforts to compare the kinematics of gas using ionized gas as a proxy for the total gas may overestimate the velocity dispersion by a significant amount in galaxies at the peak of cosmic star formation. When using the molecular gas as a tracer, our sample is not consistent with predictions from star formation models with constant efficiency, even when including transport as a source of turbulence. Feedback models with variable star formation efficiency, ϵ ff, and/or feedback efficiency, p */m *, better predict our observations.