Sub-millimetre compactness as a critical dimension to understand the Main Sequence of star-forming galaxies
Sub-millimetre compactness as a critical dimension to understand the Main Sequence of star-forming galaxies
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亚毫米致密性是理解恒星形成星系主序的关键维度
DOI：
10.1093/mnras/stab2914
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
M. Swinbank
中科院分区：
文献类型：
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作者：
A. Puglisi;E. Daddi;F. Valentino;G. Magdis;Daizhong Liu;V. Kokorev;C. Circosta;D. Elbaz;F. Bournaud;C. Gómez;S. Jin;S. Madden;M. Sargent;M. Swinbank
我们研究了77个红外线精选星系的星际介质性质与分子气体大小的关系，这些星系位于z∼1.3时，恒星质量为109.4。我是★。1012.0米和恒星形成率12。SFRFIR.−1.分子气体尺寸是在ALMA图像上测量的，该图像结合了CO(2-1)、CO(5-4)和基础连续观测，并包括对样品子集的CO(4-3)、CO(7-6)+[CI](P2−3 P1)、[CI](P1−3 P0)观测。我们的星系中有46%的星系具有致密的分子气藏，并且低于光盘的质量-大小关系。根据CO(5-4)/CO(2-1)和CO(2-1)/LIR，SF比值的示踪，位于主序及其以上的致密星系比具有扩展分子气藏的星系具有更高的CO激发和恒星形成效率。平均CO+[CI]谱线能量分布表明紧凑型比扩展源具有更高的激发强度。使用CO(2-1)和尘埃质量作为分子气体质量示踪剂，并根据它们的ISM条件定制转换因子，我们测量了致密主序星系中比扩展源更低的气体分数。我们认为，亚毫米的致密性，即分子气体与恒星大小之间的比率，是一个不可避免的信息，可以与主序列偏移一起用于描述星系的ISM性质，至少在M★>；1010.6M以上，我们的观测充分探测了主序列散射。我们的结果与在核区驱动气体、增强CO激发和恒星形成效率的合并是一致的。紧凑的主序星系与合并驱动的星暴事件之后早期的后星暴群体是一致的，强调了合并在大质量星系演化中的重要作用。
We study the interstellar medium (ISM) properties as a function of the molecular gas size for 77 infrared-selected galaxies at z ∼ 1.3, having stellar masses 109.4 . M★ . 1012.0 M and star formation rates 12 . SFRFIR . 1000M yr−1. Molecular gas sizes are measured on ALMA images that combine CO(2-1), CO(5-4) and underlying continuum observations, and include CO(4-3), CO(7-6)+[CI](P2 −3 P1), [CI](P1 −3 P0) observations for a subset of the sample. The & 46% of our galaxies have a compact molecular gas reservoir, and lie below the optical disks mass-size relation. Compact galaxies on and above the main sequence have higher CO excitation and star formation efficiency than galaxies with extended molecular gas reservoirs, as traced byCO(5-4)/CO(2-1) andCO(2-1)/LIR,SF ratios. Average CO+[CI] spectral line energy distributions indicate higher excitation in compacts relative to extended sources. Using CO(2-1) and dust masses as molecular gas mass tracers, and conversion factors tailored to their ISM conditions, we measure lower gas fractions in compact main-sequence galaxies compared to extended sources. We suggest that the sub-millimetre compactness, defined as the ratio between the molecular gas and the stellar size, is an unavoidable information to be used with the main sequence offset to describe the ISM properties of galaxies, at least above M★ > 1010.6M , where our observations fully probe the main sequence scatter. Our results are consistent with mergers driving the gas in the nuclear regions, enhancing the CO excitation and star formation efficiency. Compact main-sequence galaxies are consistent with being an early post-starburst population following a merger-driven starburst episode, stressing the important role of mergers in the evolution of massive galaxies.