论文标题
弱ICM冲击中电子加速的半分析模型
Semi-analytic Models for Electron Acceleration in Weak ICM Shocks
论文作者
论文摘要
我们提出了通过扩散冲击加速度（DSA）来解释弱冲击中电子动量分布的半分析模型。在前一种情况下，假定一小部分传入电子在冲击坡道上反映并预先加速到所谓的注入动量，$ p _ {\ rm inj} $上面粒子可以在此上进行粒子散布在冲击过渡中并参与DSA过程。这导致DSA幂律分布从反射电子的最小动量（$ p _ {\ rm ref} $）延伸到截止动量，$ p _ {\ rm eq} $，受辐射冷却的约束。在后来的情况下，假定具有截止的幂律频谱指定的化石电子也被认为也从$ p _ {\ rm ref} $从$ p _ {\ rm ref} $重新加速，最高$ p _ {\ rm eq} $ via dsa。然后，我们表明，在原位加速模型中，无线电同步器发射的幅度在很大程度上取决于冲击马赫数，而在重新加速模型中，它的变化很小。考虑到群内介质中冲击的相当动荡的性质，这种对原位加速度的极端依赖性可能与观察到的无线电遗物的相对光滑的表面亮度兼容。
We propose semi-analytic models for the electron momentum distribution in weak shocks that accounts for both in situ acceleration and re-acceleration through diffusive shock acceleration (DSA). In the former case, a small fraction of incoming electrons are assumed to be reflected at the shock ramp and pre-accelerated to the so-called injection momentum, $p_{\rm inj}$, above which particles can diffuse across the shock transition and participate in the DSA process. This leads to the DSA power-law distribution extending from the smallest momentum of reflected electrons, $p_{\rm ref}$, all the way to the cutoff momentum, $p_{\rm eq}$, constrained by radiative cooling. In the later case, fossil electrons, specified by a power-law spectrum with a cutoff, are assumed to be re-accelerated also from $p_{\rm ref}$ up to $p_{\rm eq}$ via DSA. We then show that, in the in situ acceleration model, the amplitude of radio synchrotron emission depends strongly on the shock Mach number, whereas it varies rather weakly in the re-acceleration model. Considering rather turbulent nature of shocks in the intracluster medium, such extreme dependence for the in situ acceleration might not be compatible with relatively smooth surface brightness of observed radio relics.
