爆发星系的堆积恒星形成率剖面显示出“相干”恒星形成
Stacked star formation rate profiles of bursty galaxies exhibit 'coherent' star formation
摘要：
在最近基于$z \sim 1$的3200个堆叠H $α$星系图的工作中，Nelson等人~找到“相干恒星形成”的证据：在“恒星形成主序”（MS）之上（之下）的星系的叠加SFR剖面在所有半径上都高于（低于）MS上的星系。有人可能会解释这个结果与高度爆发的恒星形成和星系沿着MS平滑演化而不是多次穿越它的证据不一致。我们分析了六个模拟星系在$z\sim1$从反馈在现实环境（FIRE）项目的方式类似的观察，以测试上述解释是否正确。堆叠SFR配置文件的趋势是定性与观察到的一致。然而，单个星系的SFR轮廓比堆叠轮廓复杂得多：前者可以是平坦的，甚至在大半径处达到峰值，因为模拟中恒星形成的高度聚集性。此外，在MS以上（以下）的个别星系的SFR配置文件是不系统的MS星系以上（以下）在所有半径。我们得出的结论是，时间平均相干恒星形成明显的堆栈观察星系是一致的高度爆发，clusified恒星形成的个别星系，并不是证据，星系演化顺利沿MS。
英文摘要：
In a recent work based on 3200 stacked H$α$ maps of galaxies at $z \sim 1$, Nelson et al.~find evidence for `coherent star formation': the stacked SFR profiles of galaxies above (below) the 'star formation main sequence' (MS) are above (below) that of galaxies on the MS at all radii. One might interpret this result as inconsistent with highly bursty star formation and evidence that galaxies evolve smoothly along the MS rather than crossing it many times. We analyze six simulated galaxies at $z\sim1$ from the Feedback in Realistic Environments (FIRE) project in a manner analogous to the observations to test whether the above interpretations are correct. The trends in stacked SFR profiles are qualitatively consistent with those observed. However, SFR profiles of individual galaxies are much more complex than the stacked profiles: the former can be flat or even peak at large radii because of the highly clustered nature of star formation in the simulations. Moreover, the SFR profiles of individual galaxies above (below) the MS are not systematically above (below) those of MS galaxies at all radii. We conclude that the time-averaged coherent star formation evident stacks of observed galaxies is consistent with highly bursty, clumpy star formation of individual galaxies and is not evidence that galaxies evolve smoothly along the MS.
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