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arXiv 1810.01596astro-ph.GA
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用ALMA计算z ~ 1.6恒星爆发的分子气体含量和燃料效率

The molecular gas content and fuel efficiency of starbursts at z ~ 1.6 with ALMA

J. Silverman, W. Rujopakarn, E. Daddi, A. Renzini, G. Rodighiero, D. Liu, A. Puglisi, M. Sargent, C. Mancini, J. Kartaltepe, D. Kashino, A. Koekemoer, N. Arimot… 展开作者

J. Silverman, W. Rujopakarn, E. Daddi, A. Renzini, G. Rodighiero, D. Liu, A. Puglisi, M. Sargent, C. Mancini, J. Kartaltepe, D. Kashino, A. Koekemoer, N. Arimoto, M. Bethermin, S. Jin, G. Magdis, T. Nagao, M. Onodera, D. Sanders, F. Valentino

摘要:

我们提出了一个分析的分子气体的性质,基于CO(2 - 1)的发射,12个星暴星系在z~1.6选择有一个提高(>~ 4倍)的恒星形成率(SFR)以上的平均恒星形成星系在同等的恒星质量。通过我们的努力,ALMA观测获得了比以前报道的更多的六个星系。由于较大的统计样本,我们显着检测,第一次在高z,一个系统性较低的L '_CO/L_IR比在星系以上的恒星形成的“主序星”(MS)。基于α_CO的估计(即,分子气体质量与L’_CO(1-0)的比率),我们将观测量(例如,L_CO/L_IR)转换为物理单位(M_gas/SFR),表示气体耗尽时间或其倒数,即恒星形成效率。我们解释的结果表明,恒星形成的效率不断增加的方式从MS的星爆制度,而气体馏分保持可比的MS星系。尽管如此,恒星形成效率或气体分数的增加之间的平衡取决于所讨论的α_CO的采用值。

英文摘要:

We present an analysis of the molecular gas properties, based on CO(2 - 1) emission, of twelve starburst galaxies at z~1.6 selected by having a boost (>~4x) in their star formation rate (SFR) above the average star-forming galaxy at an equivalent stellar mass. ALMA observations are acquired of six additional galaxies than previously reported through our effort. As a result of the larger statistical sample, we significantly detect, for the first time at high-z, a systematically lower L'_CO/L_IR ratio in galaxies lying above the star-forming `main sequence' (MS). Based on an estimate of alpha_CO (i.e., the ratio of molecular gas mass to L'_CO(1-0)), we convert the observational quantities (e.g., L'_CO/L_IR) to physical units (M_gas/SFR) that represent the gas depletion time or its inverse, the star formation efficiency. We interpret the results as indicative of the star formation efficiency increasing in a continuous fashion from the MS to the starburst regime, whereas the gas fractions remain comparable to those of MS galaxies. Although, the balance between an increase in star-formation efficiency or gas fraction depends on the adopted value of alpha_CO as discussed.

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