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arXiv 0803.1130astro-ph
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扩展的HST超新星巡天:在z>1.4时超新星Ia的速率仍然很低

The Extended HST Supernova Survey: The Rate of SNe Ia at z>1.4 Remains Low

Tomas Dahlen, Louis-Gregory Strolger, Adam G. Riess

摘要:

我们使用HST ACS在第11、12和13周期间对两个GOODS场的成像来推导Ia型超新星在0.2<z<1.8范围内的四个红移间隔的速率。与我们之前仅基于周期11观测的结果相比,我们将搜索的覆盖范围增加了2.7倍,使搜索的总面积相当于1平方度。样本现在由56颗Ia型超新星组成。我们得出的速率与我们基于第11周期观测的结果一致。特别是,在z>1.4时,少数被探测到的超新星支持了我们之前的结果,即在高红移时Ia型超新星的发生率下降,这表明在祖星形成和超新星爆炸之间有很长的时间延迟。如果用一个简单的单参数模型来描述,我们发现一个2-3 Gyr的特征延迟时间。然而,最近的一些结果,例如,低红移超新星样本和超新星宿主星系的性质表明超新星延迟时间分布是双峰的。在这个模型中,Ia型超新星速率的大部分是“快速”的,并且遵循恒星形成速率,而较小部分的速率具有较长的延迟时间,使得该通道与质量成正比。虽然我们的结果在低红移时与双峰模型完全一致,但我们在z>1.4时发现的低速率似乎与这些结果相矛盾。修正了被尘埃掩盖的恒星形成的模型至少可以解释部分差异。在这里,我们将讨论这种可能性以及协调数据和模型的其他方法。

英文摘要:

We use the HST ACS imaging of the two GOODS fields during Cycles 11, 12, and 13 to derive the Type Ia supernova rate in four redshift intervals in the range 0.2<z<1.8. Compared to our previous results based on Cycle 11 observations only, we have increased the coverage of the search by a factor 2.7, making the total area searched equivalent to one square degree. The sample now consists of 56 Type Ia supernovae. The rates we derive are consistent with our results based on the Cycle 11 observations. In particular, the few detected supernovae at z>1.4 supports our previous result that there is a drop in the Type Ia supernova rate at high redshift, suggesting a long time delay between the formation of the progenitor star and the explosion of the supernova. If described by a simple one-parameter model, we find a characteristic delay time of 2-3 Gyr. However, a number of recent results based on e.g., low redshift supernova samples and supernova host galaxy properties suggest that the supernova delay time distribution is bimodal. In this model, a major fraction of the Type Ia supernova rate is 'prompt' and follows the star formation rate, while a smaller fraction of the rate has a long delay time, making this channel proportional to mass. While our results are fully consistent with the bimodal model at low redshifts, the low rate we find at z>1.4 appears to contradict these results. Models that corrects for star formation hidden by dust may explain at least part of the differences. Here we discuss this possibility together with other ways to reconcile data and models.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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