Extremely Low Molecular Gas Content in a Compact, Quiescent Galaxy at z = 1.522
Extremely Low Molecular Gas Content in a Compact, Quiescent Galaxy at z = 1.522
复制标题
DOI：
10.3847/2041-8213/ab0c9c
复制
发表时间：
2019-02
期刊：
影响因子：
--
通讯作者：
R. Bezanson;J. Spilker;C. Williams;K. Whitaker;D. Narayanan;B. Weiner;M. Franx
中科院分区：
文献类型：
--
作者：
R. Bezanson;J. Spilker;C. Williams;K. Whitaker;D. Narayanan;B. Weiner;M. Franx
大质量星系形成的理论模型面临的最大挑战之一是早期恒星形成的规律。分子气体排出、耗尽和稳定的相对作用是不确定的，因为对高红移的猝灭或猝灭星系中的气藏的直接观测约束很少。我们给出了最近熄灭的大质量星系(z=1.522)中CO(2-1)的ALMA观测结果。这颗天体的光谱显示出强烈的巴尔默吸收线，这意味着恒星的形成在0.8Gyr之前就停止了∼。我们没有探测到CO(2-1)线发射，这给分子气体质量设置了上限。隐含的气体分数，低于在红移时恒星质量相似的典型恒星形成星系，是任何时期在这种特定恒星形成速度下最低的气体分数之一，也是迄今为止对被动星系气体含量最严格的限制。我们的观测表明，与最近声称的最近猝灭的星系中显著的冷气体相反，从星际介质中猝灭的天体的耗尽可以是有效的和相当完整的。我们探索了在高Z星系中观测到的气体分数的变化，并表明具有高恒星面密度的星系具有低的恒星面密度，类似于最近在比恒星形成率和恒星面密度之间的关联。
One of the greatest challenges to theoretical models of massive galaxy formation is the regulation of star formation at early times. The relative roles of molecular gas expulsion, depletion, and stabilization are uncertain as direct observational constraints of the gas reservoirs in quenched or quenching galaxies at high redshift are scant. We present ALMA observations of CO(2–1) in a massive ( ), recently quenched galaxy at z = 1.522. The optical spectrum of this object shows strong Balmer absorption lines, which implies that star formation ceased ∼0.8 Gyr ago. We do not detect CO(2–1) line emission, placing an upper limit on the molecular gas mass of . The implied gas fraction is , lower than typical star-forming galaxies at similar stellar masses at this redshift, among the lowest gas fractions at this specific star formation rate at any epoch, and the most stringent constraint on the gas contents of a passive galaxy to date. Our observations show that the depletion of from the interstellar medium of quenched objects can be both efficient and fairly complete, in contrast to recent claims of significant cold gas in recently quenched galaxies. We explore the variation in observed gas fractions in high-z galaxies and show that galaxies with high stellar surface density have low , similar to recent correlations between specific star formation rate and stellar surface density.