标题： 紧凑型星暴盘星系中恒星形成效率的极端变化 显示英文标题

标题： Extreme Variation in Star Formation Efficiency Across a Compact, Starbursting Disk Galaxy

摘要： We report on the internal distribution of star formation efficiency in IRAS 08339+6517 (hereafter IRAS08), using $\sim$200~pc resolution CO(2-1) observations from NOEMA. The molecular gas depletion time changes by 2 orders-of-magnitude from disk-like values in the outer parts to less than 10$^8$~yr inside the half-light radius. This translates to a star formation efficiency per free-fall time that also changes by 2 orders-of-magnitude, reaching 50-100%, different than local spiral galaxies and typical assumption of constant, low star formation efficiencies. Our target is a compact, massive disk galaxy that has SFR 10$\times$ above the $z=0$ main-sequence; Toomre $Q\approx0.5-0.7$ and high gas velocity dispersion ($\sigma_{mol}\approx 25$~km~s$^{-1}$). 我们发现IRAS08在解析的$\Sigma_{SFR}\propto\Sigma_{mol}^N$关系上与其他文献中的旋转星暴星系相似。 通过结合解析的文献研究，我们发现远离主序的距离是Kennicutt-Schmidt幂律斜率的一个强指示器，对于从100到10$^4$~M$_{\odot}$~pc$^{-2}$范围内的星暴，斜率约为$N\approx1.6$。 我们的目标与一个场景一致，在该场景中，剧烈的盘不稳定性驱动气体的快速内流。 它具有较低的Toomre-$Q$值，并且在所有半径上气体的内流时间尺度小于耗尽时间尺度，这与IRAS08中的平坦金属丰度梯度是一致的。 我们将这些结果与流行的恒星形成理论相结合，总的来说，IRAS08的观测结果与恒星形成效率为常数的理论存在最大张力。 我们的结果表明需要对更多类似的天体进行高空间分辨率的CO观测。 显示英文摘要

摘要： We report on the internal distribution of star formation efficiency in IRAS 08339+6517 (hereafter IRAS08), using $\sim$200~pc resolution CO(2-1) observations from NOEMA. The molecular gas depletion time changes by 2 orders-of-magnitude from disk-like values in the outer parts to less than 10$^8$~yr inside the half-light radius. This translates to a star formation efficiency per free-fall time that also changes by 2 orders-of-magnitude, reaching 50-100\%, different than local spiral galaxies and typical assumption of constant, low star formation efficiencies. Our target is a compact, massive disk galaxy that has SFR 10$\times$ above the $z=0$ main-sequence; Toomre $Q\approx0.5-0.7$ and high gas velocity dispersion ($\sigma_{mol}\approx 25$~km~s$^{-1}$). We find that IRAS08 is similar to other rotating, starburst galaxies from the literature in the resolved $\Sigma_{SFR}\propto\Sigma_{mol}^N$ relation. By combining resolved literature studies we find that distance from the main-sequence is a strong indicator of the Kennicutt-Schmidt powerlaw slope, with slopes of $N\approx1.6$ for starbursts from 100-10$^4$~M$_{\odot}$~pc$^{-2}$. Our target is consistent with a scenario in which violent disk instabilities drive rapid inflows of gas. It has low values of Toomre-$Q$, and also at all radii the inflow timescale of the gas is less than the depletion time, which is consistent with the flat metallicity gradients in IRAS08. We consider these results in light of popular star formation theories, in general observations of IRAS08 find the most tension with theories in which star formation efficiency is a constant. Our results argue for the need of high spatial resolution CO observations are a larger number of similar targets.