DWARF GALAXIES WITH IONIZING RADIATION FEEDBACK. I. ESCAPE OF IONIZING PHOTONS
DWARF GALAXIES WITH IONIZING RADIATION FEEDBACK. I. ESCAPE OF IONIZING PHOTONS
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具有电离辐射反馈的矮星系。
DOI：
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发表时间：
2012
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通讯作者：
Tom Abel
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作者：
Ji;M. Krumholz;J. Wise;M. Turk;N. Goldbaum;Tom Abel
我们描述了一种新的方法来模拟电离辐射和超新星反馈的类似物的低红移星系盘。在这种方法中，我们称之为恒星形成分子云（SFMC）粒子，我们使用射线跟踪技术来求解辐射传输方程的紫外光子发射的数千个不同的粒子在飞行中。结合3.8 pc的高数值分辨率，真实的恒星反馈描述有助于自我调节星星的形成。这种新的反馈方案也使我们能够研究电离光子从恒星形成团和星系中的逃逸，并研究恒星形成气体团的演化环境。通过模拟2.3 × 10 ~（11）M晕中的银盘，我们发现在1亿2000万年的时间里，旋臂上所有辐射源（不包括中心2.5kpc）的平均逃逸率在0.08%~ 5.9%之间波动，平均值为1.1%。从这些源逃逸的光子流并没有强烈的光束，但显示出与银根极成大于60°的大张角。此外，我们研究了每个SFMC粒子的逃逸分数fesc（i），以及它如何随着粒子的年龄而演变。我们发现，平均逃逸分数fesc是占主导地位的少数SFMC粒子具有高fesc（i）。平均而言，SFMC粒子的逃逸分数从其诞生时的0.27%上升到粒子寿命结束时的2.1%，600万年。这是因为SFMC粒子从它们诞生的致密气体团中漂移出来，并且因为恒星形成团周围的气体被电离辐射和超新星反馈分散。在这项研究中建立的框架带来了更深入的了解光子逃逸分数的物理从一个单独的恒星形成的团块和从星系盘。
We describe a new method for simulating ionizing radiation and supernova feedback in the analogs of low-redshift galactic disks. In this method, which we call star-forming molecular cloud (SFMC) particles, we use a ray-tracing technique to solve the radiative transfer equation for ultraviolet photons emitted by thousands of distinct particles on the fly. Joined with high numerical resolution of 3.8 pc, the realistic description of stellar feedback helps to self-regulate star formation. This new feedback scheme also enables us to study the escape of ionizing photons from star-forming clumps and from a galaxy, and to examine the evolving environment of star-forming gas clumps. By simulating a galactic disk in a halo of 2.3 × 1011 M☉, we find that the average escape fraction from all radiating sources on the spiral arms (excluding the central 2.5 kpc) fluctuates between 0.08% and 5.9% during a ∼20 Myr period with a mean value of 1.1%. The flux of escaped photons from these sources is not strongly beamed, but manifests a large opening angle of more than 60° from the galactic pole. Further, we investigate the escape fraction per SFMC particle, fesc(i), and how it evolves as the particle ages. We discover that the average escape fraction fesc is dominated by a small number of SFMC particles with high fesc(i). On average, the escape fraction from an SFMC particle rises from 0.27% at its birth to 2.1% at the end of a particle lifetime, 6 Myr. This is because SFMC particles drift away from the dense gas clumps in which they were born, and because the gas around the star-forming clumps is dispersed by ionizing radiation and supernova feedback. The framework established in this study brings deeper insight into the physics of photon escape fraction from an individual star-forming clump and from a galactic disk.