Title: The origin of scatter in the star formation rate - stellar mass relation Show Chinese title

Title: 星形成率-恒星质量关系中的散射来源

Abstract: Observations have revealed that the star formation rate (SFR) and stellar mass (M$_{\rm star}$) of star-forming galaxies follow a tight relation known as the galaxy main sequence. However, what physical information is encoded in this relation is under debate. Here, we use the EAGLE cosmological hydrodynamical simulation to study the mass dependence, evolution and origin of scatter in the SFR-M$_{\rm star}$ relation. At $z=0$, we find that the scatter decreases slightly with stellar mass from 0.35 dex at M$_{\rm star} \approx 10^9$ M$_{\odot}$ to 0.30 dex at M$_{\rm star} \gtrsim 10^{10.5}$ M$_{\odot}$, in excellent agreement with observations. The scatter decreases from $z=0$ to $z=5$ by 0.05 dex at M$_{\rm star} \gtrsim 10^{10}$ M$_{\odot}$ and by 0.15 dex for lower masses. We show that the scatter at $z=0.1$ originates from a combination of (slightly dominant) fluctuations on short time-scales ($\lesssim 1$ Gyr) that are presumably associated with self-regulation from cooling, star formation and outflows, and long time-scale ($\sim 10$ Gyr) variations related to differences in halo formation times. At high masses, differences in black hole formation efficiency cause additional scatter, but also diminish the scatter caused by different halo formation times. While individual galaxies cross the main sequence multiple times during their evolution, they fluctuate around tracks associated with their halo properties, i.e. galaxies above/below the main sequence at $z = 0.1$ tend to have been above/below the main sequence for $\gg1$ Gyr. Show Chinese abstract

Abstract: 观测表明，恒星形成率（SFR）和恒星质量（M$_{\rm star}$）在形成恒星的星系中遵循一个紧密的关系，称为星系主序列。 然而，这一关系中编码的物理信息仍存在争议。 在这里，我们使用EAGLE宇宙学流体动力学模拟来研究SFR-M$_{\rm star}$关系的质量依赖性、演化和离散度的起源。 在$z=0$，我们发现随着恒星质量的增加，离散度略有减小，从M$_{\rm star} \approx 10^9$ M$_{\odot}$的0.35 dex减少到M$_{\rm star} \gtrsim 10^{10.5}$ M$_{\odot}$的0.30 dex，这与观测结果非常一致。 散射从$z=0$减少到$z=5$，在 M$_{\rm star} \gtrsim 10^{10}$ M$_{\odot}$处减少 0.05 dex，在较低质量处减少 0.15 dex。 我们表明，$z=0.1$处的散射来源于（略微占主导地位）短时间尺度（$\lesssim 1$Gyr）的波动，这些波动可能与冷却、恒星形成和风的自我调节有关，以及长时间尺度（$\sim 10$Gyr）的变化，这些变化与晕形成时间的差异有关。 在高质量情况下，黑洞形成效率的差异导致额外的散射，但也减少了由不同晕形成时间引起的散射。 尽管单个星系在其演化过程中多次穿越主序，但它们会围绕与其晕特性相关的轨迹波动，即 在$z = 0.1$以上的/以下的星系往往已经处于$\gg1$Gyr 以上的/以下的主序线。