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arXiv 1003.3031astro-ph.GA
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麦哲伦星云中超新星爆发率和延迟时间分布

The supernova rate and delay time distribution in the Magellanic Clouds

Dan Maoz, Carles Badenes

摘要:

我们使用麦哲伦云(MC)中的超新星遗迹(SNR)作为超新星(SN)调查,“进行”了数万年,从中我们得出了当前的SN速率和SN延迟时间分布(DTD),即,假设恒星形成短暂爆发后SN速率与时间的关系。在Badenes,Maoz,& Draine(2010)中,我们编制了MCS中77个SNR的列表,并认为这是它们扩展的Sedov阶段的SNR的相当完整的记录。我们恢复的DTD通过比较观察到的SNR在这些星系中的小的个人“细胞”的每个细胞的恒星形成的历史,从解决恒星星族哈里斯和Zaritsky计算。信噪比的可见时间是Sedov相寿命,这取决于当地的环境密度。当地的密度估计HI发射,从逆施密特定律的基础上,无论是Halpha通量或解决恒星形成率,并从这些示踪剂的组合。在DTD中,我们探测到了“即时”Ia型超新星(在恒星形成的3.3亿年内爆炸),置信水平(c.l.)>99%。根据所用的密度示踪剂,每个恒星质量形成的SNe-Ia瞬发数的最佳拟合值为(2.7-11.0)x 10^{-3} /Msun。95% C.“延迟”的超新星Ia组分(从3.3亿年到哈勃时间)的范围小于1.6 x 10^{-13} SN/yr/Msun,这与老年人群的速率测量结果一致。目前MCs中的总(核心塌陷+Ia)SN率为每千年2.5-4.6 SNe(68% c.l.+系统学),或1.7-3.1 SNuM [SNe/100 yr/10^{10}Msun],与历史记录和在其他矮不规则星中测量的速率一致。相反,假设SNRs处于自由膨胀阶段,而不是Sedov阶段,则SNRs的最大年龄为6 kyr,这意味着每单位质量的MC SN速率是任何类型星系的5倍。

英文摘要:

We use the supernova remnants (SNRs) in the Magellanic Clouds (MCs) as a supernova (SN) survey, "conducted" over tens of kyr, from which we derive the current SN rate, and the SN delay time distribution (DTD), i.e., the SN rate vs. time that would follow a hypothetical brief burst of a star formation. In Badenes, Maoz, & Draine (2010) we have compiled a list of 77 SNRs in the MCS, and argued it is a fairly complete record of the SNRs in the Sedov phase of their expansions. We recover the DTD by comparing the numbers of SNRs observed in small individual "cells" in these galaxies to the star-formation histories of each cell, as calculated from resolved stellar populations by Harris & Zaritsky. The visibility times of SNRs are the Sedov-phase lifetimes, which depend on the local ambient densities. The local densities are estimated from HI emission, from an inverse Schmidt law based on either Halpha flux or on the resolved star-formation rate, and from combinations of these tracers. In the DTD, we detect "prompt" type-Ia SNe (that explode within 330 Myr of star formation) at >99% confidence level (c.l.). The best fit for the number of prompt SNe-Ia per stellar mass formed is (2.7-11.0) x 10^{-3} /Msun, depending on the density tracer used. The 95% c.l. range for a "delayed" SN Ia component (from 330 Myr to a Hubble time) is < 1.6 x 10^{-13} SN/yr/Msun, consistent with rate measurements in old populations. The current total (core-collapse+Ia) SN rate in the MCs is 2.5-4.6 SNe per millenium (68% c.l.+systematics), or 1.7-3.1 SNuM [SNe/100 yr/10^{10}Msun], in agreement with the historical record and with rates measured in other dwarf irregulars. Conversely, assuming the SNRs are in free expansion, rather than in their Sedov phase, would impose on the SNRs a maximum age of 6 kyr, and would imply a MC SN rate per unit mass that is 5 times higher than in any type of galaxy.

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