从矮星系Eu丰度推断r-过程生产场所
r-process Production Sites as inferred from Eu Abundances in Dwarf Galaxies
摘要：
最近对超暗矮星系（UFD）中$r$过程物质的观测揭示了这些元素的来源。在一些UFD中，Eu质量的上限很强，再加上在UFD、网壳II和其他矮星系中检测到的更大的质量，这意味着Eu的产生主要是由罕见的事件决定的，在任何UFD中观察到的最小Eu质量大约是每个事件产生的Eu质量的量。这与银河系中的其他独立观测结果一致。我们估计，使用模型独立的似然分析，率和Eu（Fe）的质量产生的每$r$过程（Fe生产）事件的矮星系，包括经典的矮星和UFD。Fe产生事件的质量和速率与正常的核塌缩超新星~（ccSN）的情况一致。每个事件的Eu质量是$3\times 10^{-5}M_{\odot}<\tilde{m}_{\rm Eu}<2\times 10^{-4}M_{\odot}$，对应于总$r$ -每个事件的过程质量$6\times 10^{-3}M_{\odot}<\tilde{m}_{r-process}<4\times 10^{-2}M_{\odot}$。与ccSNe发生率相比，$r$ -过程事件发生率为$2.5\times 10^{-4}<R_{rp/SN}<1.4\times 10^{-3}$。这些值与我们银河系中观测到的Eu总质量一致，表明矮星系和银河系中产生$r$过程事件的机制相同，并且它可能是宇宙中产生$r$过程元素的主导机制。结果与中子星合并的估计是一致的，但不能排除其他罕见的核心崩溃的情况下，提供他们产生了显着的$r$过程中的材料，每个事件。
英文摘要：
Recent observations of $r$-process material in ultra-faint dwarf galaxies (UFDs) shed light on the sources of these elements. Strong upper limits on the Eu mass in some UFDs combined with detections of much larger masses in a UFD, Reticulum II, and other dwarf galaxies imply that Eu production is dominated by rare events, and that the minimal Eu mass observed in any UFD is approximately the amount of Eu mass produced per event. This is consistent with other independent observations in the Galaxy. We estimate, using a model independent likelihood analysis, the rate and Eu (Fe) mass produced per $r$-process (Fe production) event in dwarf galaxies including classical dwarfs and UFDs. The mass and rate of the Fe production events are consistent with the normal core-collapse supernova~(ccSN) scenario. The Eu mass per event is $3\times 10^{-5}M_{\odot}<\tilde{m}_{\rm Eu}<2\times 10^{-4}M_{\odot}$, corresponding to a total $r$-process mass per event of $6\times 10^{-3}M_{\odot}<\tilde{m}_{r-process}<4\times 10^{-2}M_{\odot}$. The rate of $r$-process events is $2.5\times 10^{-4}<R_{rp/SN}<1.4\times 10^{-3}$ as compared with the ccSNe rate. These values are consistent with the total Eu mass observed in our own Galaxy, suggesting that the same mechanism is behind the production of $r$-process events in both dwarf galaxies and the Milky Way, and that it may be the dominant mechanism for production of $r$-process elements in the Universe. The results are consistent with neutron star mergers estimates, but cannot rule out other rare core collapse scenarios, provided that they produce a significant amounts of $r$-process material per event.
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