ALMA CO Observations of the Host Galaxies of Long-duration Gamma-Ray Bursts. I. Molecular Gas Scaling Relations
ALMA CO Observations of the Host Galaxies of Long-duration Gamma-Ray Bursts. I. Molecular Gas Scaling Relations
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DOI：
10.3847/1538-4357/ab7992
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发表时间：
2020-02
期刊：
影响因子：
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通讯作者：
B. Hatsukade;K. Ohta;T. Hashimoto;K. Kohno;K. Nakanishi;Y. Niino;Y. Tamura
中科院分区：
文献类型：
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作者：
B. Hatsukade;K. Ohta;T. Hashimoto;K. Kohno;K. Nakanishi;Y. Niino;Y. Tamura
本文介绍了利用阿塔卡玛大型毫米/亚毫米波射电望远镜阵对14个z = 0.1-2.5的长持续时间伽玛射线暴（GRB）宿主星系的CO观测结果。我们成功地在8个宿主（z = 0.3-2）中检测到CO（3-2）或CO（4-3）发射，这使具有CO检测的GRB宿主的样本量增加了一倍多。推导出的分子气体质量为Mgas =（0.2-6）× 1010 M Ω，假设金属度依赖的CO到H2的转换因子。通过使用具有分子气体估计的最大GRB宿主样本（总共25个，其中14个检测到CO），包括文献中的结果，我们将分子气体性质与其他恒星形成星系（SFG）的分子气体性质进行了比较。与其他红移相近的SFG相比，GRB宿主倾向于具有更高的分子气体质量分数（μgas）和更短的气体耗尽时标（tdepl），特别是在z ≥ 1处。这可能是伽玛射线暴宿主的一个共同特性，也可能是由于选择了通常位于主序线之上的靶点而产生的一种效应。为了消除选择偏差的影响，我们分析了μgas和tdepl作为距主层序线（δMS）的距离的函数。我们发现，GRB宿主与其他SFG遵循相同的标度关系，μgas随δMS的增加而增加，tdepl随δMS的增加而减小.没有观察到分子气体赤字相比，类似的星星形成速率和恒星质量的其他SFG。这些发现表明，相同的星星的形成机制，预计将发生在伽玛射线暴主机在其他SFG。
We present the results of CO observations toward 14 host galaxies of long-duration gamma-ray bursts (GRBs) at z = 0.1–2.5 by using the Atacama Large Millimeter/submillimeter Array. We successfully detected CO (3–2) or CO (4–3) emission in eight hosts (z = 0.3–2), which more than doubles the sample size of GRB hosts with CO detection. The derived molecular gas mass is Mgas = (0.2–6) × 1010 M⊙ assuming metallicity-dependent CO-to-H2 conversion factors. By using the largest sample of GRB hosts with molecular gas estimates (25 in total, of which 14 are CO detected), including results from the literature, we compared molecular gas properties with those of other star-forming galaxies (SFGs). The GRB hosts tend to have a higher molecular gas mass fraction (μgas) and a shorter gas depletion timescale (tdepl) as compared with other SFGs at similar redshifts, especially at z ≲ 1. This could be a common property of GRB hosts or an effect introduced by the selection of targets that are typically above the main-sequence line. To eliminate the effect of selection bias, we analyzed μgas and tdepl as a function of the distance from the main-sequence line (δMS). We find that the GRB hosts follow the same scaling relations as other SFGs, where μgas increases and tdepl decreases with increasing δMS. No molecular gas deficit is observed when compared to other SFGs of similar star formation rate and stellar mass. These findings suggest that the same star formation mechanism is expected to be happening in GRB hosts as in other SFGs.