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arXiv 1405.7410astro-ph.GA
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在z~0.1时星团,湍流盘星系的极端气体分数

Extreme gas fractions in clumpy, turbulent disk galaxies at z~0.1

David B. Fisher, Karl Glazebrook, Alberto Bolatto, Danail Obreschkow, Erin Mentuch-Cooper, Emily Wisnioski, Robert BAssett, Roberto G. Abraham, Ivana Damjanov, … 展开作者

David B. Fisher, Karl Glazebrook, Alberto Bolatto, Danail Obreschkow, Erin Mentuch-Cooper, Emily Wisnioski, Robert BAssett, Roberto G. Abraham, Ivana Damjanov, Andy Green, Peter McGregor

摘要:

在这封信中,我们报告了CO通量的发现,这表明在附近的宇宙(z ~ 0.1)中看到的三个盘状星系中有非常高的气体分数。这些星系是作为新组装大质量天体动力学(DYNAMICS of Newly Assembled Massive Objects)调查的一部分进行研究的。哈勃太空望远镜对这些天体的高分辨率成像揭示了星系体内存在大型恒星形成团块,而红移的H α空间分辨光谱揭示了高色散旋转盘的存在。这些星系的内部动力学状态类似于在更高的红移(1 < z < 3)下看到的盘系统。利用Plateau de Bure干涉仪对CO(1-0)的观测,我们发现气体分数为20-30%,耗尽时间为tdep ~ 0.5 Gyr(假设一个类似银河系的CO转换因子)。这些性质不同于那些具有可比的特定恒星形成率的低红移星系的预期性质,但它们对于高z星系是正常的。星系的气体分数和红移之间的简并打破,我们表明,耗尽时间每特定的恒星形成率的星系是密切相关的气体分数,独立的红移。我们还表明,我们的两个本地目标的气体动力学对应于那些预期从不稳定的磁盘,再次类似于高Z磁盘的动态。这些结果提供的证据表明,星系是本地类似的cloudos,湍流盘,这是经常发现在高红移。

英文摘要:

In this letter we report the discovery of CO fluxes, suggesting very high gas fractions in three disk galaxies seen in the nearby Universe (z ~ 0.1). These galaxies were investigated as part of the DYnamics of Newly Assembled Massive Objects (DYNAMO) survey. High-resolution Hubble Space Telescope imaging of these objects reveals the presence of large star forming clumps in the bodies of the galaxies, while spatially resolved spectroscopy of redshifted Halpha reveals the presence of high dispersion rotating disks. The internal dynamical state of these galaxies resembles that of disk systems seen at much higher redshifts (1 < z < 3). Using CO(1-0) observations made with the Plateau de Bure Interferometer, we find gas fractions of 20-30% and depletion times of tdep ~ 0.5 Gyr (assuming a Milky Way-like CO conversion factor). These properties are unlike those expected for low- redshift galaxies of comparable specific star formation rate, but they are normal for their high-z counterparts. DYNAMO galaxies break the degeneracy between gas fraction and redshift, and we show that the depletion time per specific star formation rate for galaxies is closely tied to gas fraction, independent of redshift. We also show that the gas dynamics of two of our local targets corresponds to those expected from unstable disks, again resembling the dynamics of high-z disks. These results provide evidence that DYNAMO galaxies are local analogues to the clumpy, turbulent disks, which are often found at high redshift.

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