The Galaxy Starburst/Main-sequence Bimodality over Five Decades in Stellar Mass at z ≈ 3–6.5
The Galaxy Starburst/Main-sequence Bimodality over Five Decades in Stellar Mass at z ≈ 3–6.5
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DOI：
10.3847/1538-4357/ac5d39
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发表时间：
2021-12
期刊：
影响因子：
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通讯作者：
P. Rinaldi;K. Caputi;Sophie E. van Mierlo;M. Ashby;G. Caminha;E. Iani
中科院分区：
文献类型：
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作者：
P. Rinaldi;K. Caputi;Sophie E. van Mierlo;M. Ashby;G. Caminha;E. Iani
我们研究了恒星质量（5.5 μ log 10（M*/M *）<$10.5）z = 3-6.5的恒星形成星系近50年来恒星质量（M *）与星星形成率（SFR）之间的关系。这一前所未有的覆盖范围是可能的，这要归功于对空白非透镜场（COSMOS/SMUVS）和星团透镜场（哈勃前沿场）的联合分析，这使我们能够达到非常低的恒星质量。先前的工作已经揭示了在SFR-M * 平面中存在一个明显的双峰性，其中有一个星星形成主序星和一个z = 4-5的星暴云。在这里，我们表明，这种双峰性扩展到所有的恒星形成星系，是有效的，在整个红移范围z <$3 -6.5。我们发现，在这些红移下，恒星爆发至少占所有恒星形成星系的20%，M *<$109 M <$，并在z = 4-5时达到40%的峰值。更重要的是，在这些红移的总SFR预算的60%-90%包含在星暴星系，表明星暴模式的星星形成是占主导地位的高红移。几乎所有log 10（M*/M）为<$8.5的低恒星质量星暴的年龄都与星暴事件的典型时间尺度相当，这表明这些星系正在形成过程中被捕获。有趣的是，星系形成模型未能预测星暴/主序星双峰和星暴的整体，这表明星暴现象可能是由物理过程发生在较小的尺度比这些模型探测。
We study the relation between stellar mass (M *) and star formation rate (SFR) for star-forming galaxies over approximately five decades in stellar mass ( 5.5≲log10(M*/M⊙)≲10.5 ) at z ≈ 3–6.5. This unprecedented coverage has been possible thanks to the joint analysis of blank non-lensed fields (COSMOS/SMUVS) and cluster lensing fields (Hubble Frontier Fields) that allow us to reach very low stellar masses. Previous works have revealed the existence of a clear bimodality in the SFR–M * plane with a star formation Main Sequence and a starburst cloud at z ≈ 4–5. Here we show that this bimodality extends to all star-forming galaxies and is valid in the whole redshift range z ≈ 3–6.5. We find that starbursts constitute at least ≈20% of all star-forming galaxies with M * ≳ 109 M ⊙ at these redshifts and reach a peak of 40% at z = 4–5. More importantly, 60%–90% of the total SFR budget at these redshifts is contained in starburst galaxies, indicating that the starburst mode of star formation is dominant at high redshifts. Almost all the low stellar mass starbursts with log10(M*/M⊙)≲8.5 have ages comparable to the typical timescales of a starburst event, suggesting that these galaxies are being caught in the process of formation. Interestingly, galaxy formation models fail to predict the starburst/main-sequence bimodality and starbursts overall, suggesting that the starburst phenomenon may be driven by physical processes occurring at smaller scales than those probed by these models.