Molecular Gas Contents and Scaling Relations for Massive, Passive Galaxies at Intermediate Redshifts from the LEGA-C Survey
Molecular Gas Contents and Scaling Relations for Massive, Passive Galaxies at Intermediate Redshifts from the LEGA-C Survey
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DOI：
10.3847/1538-4357/aac438
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发表时间：
2018-05
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通讯作者：
J. Spilker;R. Bezanson;I. Barišić;E. Bell;Claudia del P. Lagos;M. Maseda;A. Muzzin;C. Pacifici;D. Sobral;C. Straatman;A. V. D. Wel;P. V. Dokkum;B. Weiner;K. Whitaker;C. Williams;Po-Feng Wu
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作者：
J. Spilker;R. Bezanson;I. Barišić;E. Bell;Claudia del P. Lagos;M. Maseda;A. Muzzin;C. Pacifici;D. Sobral;C. Straatman;A. V. D. Wel;P. V. Dokkum;B. Weiner;K. Whitaker;C. Williams;Po-Feng Wu
十年的研究已经确定，恒星形成星系的分子气体性质遵循一致的标度关系，直到z = 3，这表明分子气体，星星形成和恒星生长之间的相互作用具有显着的规律性。然而，被动星系被认为是气体贫乏的，因此是暗淡的，因此对本机宇宙之外的被动星系中的分子气体知之甚少。在这里，我们展示了阿塔卡马深层大型毫米/亚毫米阵列对八个大质量（Mstar 1011 M⊙）星系z 0.7处CO（2-1）发射的观测，这些星系被选择为比该红移处的恒星形成序列低3-10倍，来自大型早期星系天体物理普查调查。我们显著地检测了一半的样品，发现分子气体分数为10.1。我们发现，分子和恒星的旋转轴是大致一致的，认为分子气体没有吸积后，星系变得静止。我们发现，从恒星形成人口外推的标度关系overpredict的气体分数和气体耗尽时间的被动对象，这表明存在一个休息或大的增加，在这些关系中的分散在低特定的星星形成率。最后，我们发现，我们观察到的被动星系在中等红移的气体分数自然是一致的演变成本地，大规模的早期型星系的持续低级别星星形成，没有必要进一步的气体吸积或动态稳定的气体水库在干预60亿年。
A decade of study has established that the molecular gas properties of star-forming galaxies follow coherent scaling relations out to z ∼ 3, suggesting remarkable regularity of the interplay between molecular gas, star formation, and stellar growth. Passive galaxies, however, are expected to be gas-poor and therefore faint, and thus little is known about molecular gas in passive galaxies beyond the local universe. Here we present deep Atacama Large Millimeter/submillimeter Array observations of CO(2–1) emission in eight massive (Mstar ∼ 1011 M⊙) galaxies at z ∼ 0.7 selected to lie a factor of 3–10 below the star-forming sequence at this redshift, drawn from the Large Early Galaxy Astrophysics Census survey. We significantly detect half the sample, finding molecular gas fractions ≲0.1. We show that the molecular and stellar rotational axes are broadly consistent, arguing that the molecular gas was not accreted after the galaxies became quiescent. We find that scaling relations extrapolated from the star-forming population overpredict both the gas fraction and gas depletion time for passive objects, suggesting the existence of either a break or large increase in scatter in these relations at low specific star formation rate. Finally, we show that the gas fractions of the passive galaxies we have observed at intermediate redshifts are naturally consistent with evolution into local, massive early-type galaxies by continued low-level star formation, with no need for further gas accretion or dynamical stabilization of the gas reservoirs in the intervening 6 billion years.