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arXiv 0812.2479astro-ph
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高红移遗迹HII区的辐射反馈

Radiative Feedback in Relic HII Regions at High-Redshift

Andrei Mesinger, Greg L. Bryan, Zoltan Haiman

摘要:

来自早期天体物理学来源的紫外线辐射可能对附近原星系中随后的恒星形成产生巨大影响。在这里,我们研究的辐射反馈的第一,短命的恒星使用流体动力学模拟与瞬态紫外线背景(UVB)和持久的莱曼-沃纳背景(LWB)的不同强度。我们扩展了Mesinger等人(2006)之前的工作,研究了一个更典型的区域,该区域的原星系在较低红移z~13-20处形成,该区域可能在大部分再电离之前的时期。我们证实了我们以前的结果,反馈的遗迹HII地区造成的这种瞬态辐射,本身是瞬态的。反馈效应在大约30%的哈勃时间后逐渐减弱,并且相同的临界比强度J_UV~0.1 x 10^{-21}尔格/s/cm ^2/Hz/sr将正反馈和负反馈区分开来。此外,我们发现了第二集的最终正反馈晕尚未崩溃时,他们的祖先地区暴露于瞬态UVB。无论UVB的强度如何,这种最终的正反馈都出现在所有运行中。然而,这种反馈机制对Lyman-Werner辐射的存在非常敏感,在J_LW>10^{-3} x 10^{-21} ergs/s/cm^2/Hz/sr的相当温和的背景强度下,显著的效应消失。我们得出结论,在遗迹HII区的紫外辐射反馈,虽然是一个复杂的过程,似乎不太可能对宇宙学再电离的进展产生重大影响,前提是目前对PopIII恒星的寿命和光度的估计是准确的。更有可能的是,LWB的建立最终控制反馈强度,直到可以建立持久的UV背景。[删节]

英文摘要:

UV radiation from early astrophysical sources could have a large impact on subsequent star formation in nearby protogalaxies. Here we study the radiative feedback from the first, short-lived stars using hydrodynamical simulations with transient UV backgrounds (UVBs) and persistent Lyman-Werner backgrounds (LWBs) of varying intensity. We extend our prior work in Mesinger et al. (2006), by studying a more typical region whose proto-galaxies form at lower redshifts, z~13-20, in the epoch likely preceding the bulk of reionization. We confirm our previous results that feedback in the relic HII regions resulting from such transient radiation, is itself transient. Feedback effects dwindle away after ~30% of the Hubble time, and the same critical specific intensity of J_UV~0.1 x 10^{-21} ergs/s/cm^2/Hz/sr separates positive and negative feedback regimes. Additionally, we discover a second episode of eventual positive feedback in halos which have not yet collapsed when their progenitor regions were exposed to the transient UVB. This eventual positive feedback appears in all runs, regardless of the strength of the UVB. However, this feedback regime is very sensitive to the presence of Lyman-Werner radiation, and notable effects disappear under fairly modest background intensities of J_LW>10^{-3} x 10^{-21} ergs/s/cm^2/Hz/sr. We conclude that UV radiative feedback in relic HII regions, although a complicated process, seems unlikely to have a major impact on the progress of cosmological reionization, provided that present estimates of the lifetime and luminosity of a PopIII star are accurate. More likely is that the build-up of the LWB ultimately governs the feedback strength until a persistent UV background can be established. [abridged]

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