Title: Turn up the light: Radiative efficiency of protostars at birth Show Chinese title

Title: 调高光线：恒星诞生时的辐射效率

Abstract: Early stages of stellar birth comprise of a two-step process involving the formation of two hydrostatic cores. The second step of gravitational collapse sets the radiative efficiency and accretion rate of the young protostar. These two parameters, of prime importance for protostellar evolution, dictate the luminosities and thus play a key role in deciphering the current discrepancy between observational surveys and theoretical models. In this letter, we provide quantitative estimates on the evolution of the radiative efficiency and accretion rate obtained from self-consistent, high-resolution, radiative hydrodynamic simulations performed using the codes PLUTO and RAMSES. The main highlight of our result is that the radiative efficiency reaches unity, that is, supercriticality, relatively quickly after protostellar birth. Supercriticality at the accretion shock is a necessary condition for cold accretion. Our results thus support a rapid transition to the cold accretion scenario, which is one of the assumptions used in Pre-Main Sequence (PMS) models working towards solutions to explain observational data. We briefly discuss the implications of the time evolution of the radiative efficiency factor in the context of the luminosity problem, the Protostellar Luminosity Function (PLF), PMS evolution, accurate sink properties, and the stellar Initial Mass Function (IMF). Show Chinese abstract

Abstract: 恒星形成的早期阶段包括一个两步过程，涉及两个流体静力核心的形成。 引力坍缩的第二步设定了年轻原恒星的辐射效率和吸积率。 这两个参数对于原恒星演化至关重要，决定了光度，并在解释观测调查与理论模型之间的当前差异中起着关键作用。 在本信中，我们提供了来自自洽、高分辨率、辐射流体动力学模拟的定量估计，这些模拟使用代码PLUTO和RAMSES进行。 我们结果的主要亮点是，辐射效率在原恒星诞生后相对较快地达到1，即超临界状态。 在吸积冲击处的超临界状态是冷吸积的必要条件。 因此，我们的结果支持快速过渡到冷吸积情景，这是用于解决解释观测数据的预主序（PMS）模型的一个假设。 我们简要讨论了辐射效率因子的时间演化在光度问题、原恒星光度函数（PLF）、PMS演化、准确的汇属性以及恒星初始质量函数（IMF）背景下的意义。