Stellar feedback by radiation pressure and photoionization
Laura V. Sales, Federico Marinacci, Volker Springel, Margarita Petkova
备注：
18 pages, 19 figures (main results presented in 13 pages, 10 figures; extended appendix for RT tests with extra 9 figures). Accepted for publication in MNRAS after tiny changes
The relative impact of radiation pressure and photoionization feedback from young stars on surrounding gas is studied with hydrodynamic radiative transfer (RT) simulations. The calculations focus on the single-scattering (direct radiation pressure) and optically thick regime, and adopt a moment-based RT-method implemented in the moving-mesh code AREPO. The source luminosity, gas density profile and initial temperature are varied. At typical temperatures and densities of molecular clouds, radiation pressure drives velocities of order ~20 km/s over 1-5 Myr; enough to unbind the smaller clouds. However, these estimates ignore the effects of photoionization that naturally occur concurrently. When radiation pressure and photoionization act together, the latter is substantially more efficient, inducing velocities comparable to the sound speed of the hot ionized medium (10-15 km/s) on timescales far shorter than required for accumulating similar momentum with radiation pressure. This mismatch allows photoionization to dominate the feedback as the heating and expansion of gas lowers the central densities, further diminishing the impact of radiation pressure. Our results indicate that a proper treatment of the impact of young stars on the interstellar medium needs to primarily account for their ionization power whereas direct radiation pressure appears to be a secondary effect. This conclusion may change if extreme boosts of the radiation pressure by photon trapping are assumed.
Excess entropy and energy feedback from within cluster cores up to r$_{200}$
我们估计的“非引力”的熵注入配置文件，$ΔK$，并由此产生的能量反馈配置文件，$ΔE$，17个集群使用普朗克SZ和ROSAT X射线观测，跨越一个大的径向范围从$0.2r_{500}$到$r_{200}$的集群内介质。反馈配置文件的估计通过比较所观察到的熵，在固定的气体质量壳，与理论熵的非辐射流体动力学模拟预测的配置文件。在我们的分析中，我们包括非热压力和气体聚集。将非热压力和结块包括在内导致$r_{500}$和$r_{200}$的估计值改变10 - 20%。当不考虑成块性时，其导致低估$r_{500}$处的$ΔK\approx300$ keV cm $^2$和$r_{200}$处的$ΔK\approx1100$ keV cm $^2$。另一方面，忽略非热压力会导致在$r_{500}$处高估$ΔK\approx 100$ keV cm $^2$，而在$r_{200}$处低估$ΔK\approx450$ keV cm $^2$。对于估计的反馈能量，我们发现，忽略成团导致低估的能量每粒子$ΔE\approx1$千电子伏在$r_{500}$和$ΔE\approx1.5$千电子伏在$r_{200}$。类似地，忽略非热压力会导致在$r_{500}$处高估$ΔE\approx0.5$ keV，而在$r_{200}$处低估$ΔE\approx0.25$ keV。我们发现熵地板的$ΔK\appro…
Radiation pressure, absorption and AGN feedback in the Chandra Deep Fields
活动星系核（AGN）中央引擎周围存在吸收气体是这些天体的共同特征。最近的工作着眼于气体的尘埃成分的影响，以及它如何提高辐射压力，使含尘气体可以有一个较低的有效爱丁顿限制比电离气体。在这项工作中，我们使用多波长的数据和X射线光谱从2毫秒曝光的钱德拉深场北和钱德拉深场南调查，以确定活动星系核的爱丁顿比和氢柱密度。它们的分布进行比较，当考虑到尘埃和气体之间的耦合预测。我们的最终样本包括来自两个领域的234个对象，最大和最深的AGN样本，这种比较已经取得了最新的。我们发现，样本中的活动星系核大多倾向于在低爱丁顿比（通常在1 e-4和1 e-1之间）和高柱密度（> 1 e 22 cm^-2）下发现，而黑洞的质量在~ 1 e 8和1 e 9太阳质量之间。它们的分布与增强辐射压力模型的预期一致，避开了我们预测存在外流的区域。我们还研究了活动星系核辐射压力和引力势之间的平衡如何影响星系核球中云的行为，并描述了一种增强的辐射压力可以导致黑洞/星系标度关系的基本平面的情况。
