从扩展的GOODS/HST超新星巡天获得Ia型超新星的经验延迟时间分布
Empirical Delay Time Distributions of Type Ia Supernovae From The Extended GOODS/HST Supernova Survey
摘要：
使用哈勃太空望远镜ACS成像的GOODS北，南领域在周期11，12和13，我们得出的经验约束的延迟时间分布函数的Ia型超新星。我们将之前的分析扩展到了0.2<z<1.8范围内的56个Ia超新星的三年样本，使用马尔可夫链蒙特卡罗来确定最佳拟合的单峰延迟时间分布函数。该测试最终将恒星形成率密度历史与来自GOODS/HST-SN调查的未分类的超新星Ia体积率历史进行比较，揭示了超新星Ia延迟时间分布严格限制在3-4 Gyrs（>95%置信度）。该结果难以用任何固有的延迟时间分布函数（双峰或其他）来解决，其中大部分（例如，>10%）的事件是“爆炸”，从形成到爆炸需要不到1 Gyr的时间。然而，这一结果强烈地受到了在z>1.2时Ia型超新星数量下降的影响。HST-SN数据的子样本局限于较低的红移（z<1），显示出合理的延迟时间分布，主要是由瞬发事件，这是更一致的结果，从低红移超新星样本和超新星宿主星系的属性。在这种情况下，相当一部分z>1.2的超新星被尘埃所掩盖，这可能部分解释了低z和高z结果的差异。其他可能的解决方案可能包括环境依赖性（如气相金属丰度），影响祖机制的效率，特别是在早期宇宙。
英文摘要：
Using the Hubble Space Telescope ACS imaging of the GOODS North and South fields during Cycles 11, 12, and 13, we derive empirical constraints on the delay-time distribution function for type Ia supernovae. We extend our previous analysis to the three-year sample of 56 SNe Ia over the range 0.2<z<1.8, using a Markov chain Monte Carlo to determine the best-fit unimodal delay-time distribution function. The test, which ultimately compares the star formation rate density history to the unbinned volumetric SN Ia rate history from the GOODS/HST-SN survey, reveals a SN Ia delay-time distribution that is tightly confined to 3-4 Gyrs (to >95% confidence). This result is difficult to resolve with any intrinsic delay-time distribution function (bimodal or otherwise), in which a substantial fraction (e.g., >10%) of events are ``prompt'', requiring less than approximately 1 Gyr to develop from formation to explosion. The result is, however, strongly motivated by the decline in the number of SNe Ia at z>1.2. Sub-samples of the HST-SN data confined to lower redshifts (z<1) show plausible delay-time distributions that are dominated by prompt events, which is more consistent with results from low-redshift supernova samples and supernova host galaxy properties. Scenarios in which a substantial fraction of z>1.2 supernovae are extraordinarily obscured by dust may partly explain the differences in low-z and high-z results. Other possible resolutions may include environmental dependencies (such as gas-phase metallicity) that affect the progenitor mechanism efficiency, especially in the early universe.
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