Molecular Gas Properties in the Host Galaxy of GRB 080207
Molecular Gas Properties in the Host Galaxy of GRB 080207
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DOI：
10.3847/1538-4357/ab1649
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发表时间：
2019-04
期刊：
影响因子：
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通讯作者：
B. Hatsukade;T. Hashimoto;K. Kohno;K. Nakanishi;K. Ohta;Y. Niino;Y. Tamura;L. V. Tóth
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文献类型：
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作者：
B. Hatsukade;T. Hashimoto;K. Kohno;K. Nakanishi;K. Ohta;Y. Niino;Y. Tamura;L. V. Tóth
本文介绍了用Karl G. Jansky甚大天线阵和阿塔卡马大型毫米/亚毫米天线阵。在CO（1-0）和CO（4-3）中检测到宿主，成为文献中首次检测到CO（2-1）和CO（3-2）结合两个以上CO跃迁的伽马射线暴（GRB）宿主。采用一个与金属度相关的CO到H2的转换因子，我们得到了一个分子气体质量为Mgas = 8.7 × 1010 M <$，这将宿主置于Mgas-恒星形成率（SFR）平面上的一系列正常恒星形成星系中。一个适合远红外毫米测光的修正黑体得到尘埃温度为37 K，尘埃质量为M dust = 1.5 × 108 M dust。空间分辨的CO（4-3）观测使我们能够检查主机的运动学。CO速度场显示出明显的旋转，并由旋转主导的盘模型再现，旋转速度为350 km s−1，半光半径为2.4 kpc。CO谱线能量分布与星暴星系相似，说明它们处于高激发状态。在类似的红移下，主星系和正常星系（主序星）的分子气体性质的比较显示，它们有着共同的性质，如气体质量分数、气体耗尽时间尺度、气体与尘埃的比率、在Mgas-SFR（或表面密度）关系中的位置和运动学，这表明长持续时间的伽玛暴可以发生在z = 2的正常恒星形成环境中。
We present the results of CO(1–0) and CO(4–3) observations of the host galaxy of a long-duration gamma-ray burst GRB 080207 at z = 2.0858 by using the Karl G. Jansky Very Large Array and the Atacama Large Millimeter/submillimeter Array. The host is detected in CO(1–0) and CO(4–3), becoming the first case for a gamma-ray burst (GRB) host with more than two CO transitions detected combined with CO(2–1) and CO(3–2) in the literature. Adopting a metallicity-dependent CO-to-H2 conversion factor, we derive a molecular gas mass of Mgas = 8.7 × 1010 M⊙, which places the host in a sequence of normal star-forming galaxies in an Mgas–star formation rate (SFR) plane. A modified blackbody fit to the far-infrared–millimeter photometry results in a dust temperature of 37 K and a dust mass of Mdust = 1.5 × 108 M⊙. The spatially resolved CO(4–3) observations allow us to examine the kinematics of the host. The CO velocity field shows a clear rotation and is reproduced by a rotation-dominated disk model with a rotation velocity of 350 km s−1 and a half-light radius of 2.4 kpc. The CO spectral line energy distribution derived from the four CO transitions is similar to that of starburst galaxies, suggesting a high excitation condition. Comparison of molecular gas properties between the host and normal (main-sequence) galaxies at similar redshifts shows that they share common properties such as gas mass fraction, gas depletion timescale, gas-to-dust ratio, location in the Mgas–SFR (or surface density) relation, and kinematics, suggesting that long-duration GRBs can occur in normal star-forming environments at z ∼ 2.