标题： Ia型超新星在球状星团中第二代恒星形成中的作用 显示英文标题

标题： On the role of Type Ia supernovae in the second generation star formation in globular clusters

摘要： 通过三维流体动力学模拟，我们研究了I型超新星（SNe）爆炸如何影响球状星团（GC）中第二代（SG）恒星的恒星形成历史和化学特性。假设SG恒星在第一代渐近巨星分支（AGB）恒星开始释放其抛射物后形成；在此阶段，系统会吸积外部气体，并且I型超新星开始爆炸，形成高温稀薄的气泡。鉴于I型超新星爆炸时间存在较大不确定性，我们测试了两种不同的“延迟时间”值。我们为外部气体密度运行了两种不同的模型：在低密度情景下，短延迟时间使得爆炸在SG恒星形成初期就开始，从而在其最早期阶段就阻止了恒星形成。外部气体很难渗透到系统中，因此大多数SG恒星表现出极端的氦丰度（Y > 0.33）。低密度模型中延迟的超新星爆炸具有更长的SG恒星形成时期，并包括具有适度氦增丰的SG恒星。相反，高密度模型受超新星爆炸的影响较弱，最终的SG质量与没有超新星Ia的情况相似。大部分恒星由AGB抛射物和原始气体的混合物形成，并具有适度的氦增丰。我们表明，来自超新星Ia的气体可能产生一个$\sim 0.14$ dex的铁扩散，这与银河系约20%的GC中发现的扩散一致，表明超新星Ia可能在这些GC子样本的形成中发挥了关键作用。 显示英文摘要

摘要： By means of 3D hydrodynamic simulations, we study how Type Ia supernovae (SNe) explosions affect the star formation history and the chemical properties of second generation (SG) stars in globular clusters (GC). SG stars are assumed to form once first generation asymptotic giant branch (AGB) stars start releasing their ejecta; during this phase, external gas is accreted by the system and SNe Ia begin exploding, carving hot and tenuous bubbles. Given the large uncertainty on SNe Ia explosion times, we test two different values for the 'delay time'. We run two different models for the external gas density: in the low-density scenario with short delay time, the explosions start at the beginning of the SG star formation, halting it in its earliest phases. The external gas hardly penetrates the system, therefore most SG stars present extreme helium abundances (Y > 0.33). The low-density model with delayed SN explosions has a more extended SG star formation epoch and includes SG stars with modest helium enrichment. On the contrary, the high-density model is weakly affected by SN explosions, with a final SG mass similar to the one obtained without SNe Ia. Most of the stars form from a mix of AGB ejecta and pristine gas and have a modest helium enrichment. We show that gas from SNe Ia may produce an iron spread of $\sim 0.14$ dex, consistent with the spread found in about 20% of Galactic GCs, suggesting that SNe Ia might have played a key role in the formation of this sub-sample of GCs.