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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Searching for the missing baryons in clusters
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Searching for the missing baryons in clusters

机译：搜索簇中缺失的重子

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摘要

Observations of clusters of galaxies suggest that they contain fewer baryons (gas plus stars) than the cosmic baryon fraction. This "missing baryon" puzzle is especially surprising for the most massive clusters, which are expected to be representative of the cosmic matter content of the universe (baryons and dark matter). Here we show that the baryons may not actually be missing from clusters, but rather are extended to larger radii than typically observed. The baryon deficiency is typically observed in the central regions of clusters (-0.5 the virial radius). However, the observed gas-density profile is significantly shallower than the mass-density profile, implying that the gas is more extended than the mass and that the gas fraction increases with radius. We use the observed density profiles of gas and mass in clusters to extrapolate the measured baryon fraction as a function of radius and as a function of cluster mass. We find that the baryon fraction reaches the cosmic value near the virial radius for all groups and clusters above ～5 × 10~(13)h_(72)~(-1)W_☉. This suggests that the baryons are not missing, they are simply located in cluster outskirts. Heating processes (such as shock-heating of the intracluster gas, supernovae, and Active Galactic Nuclei feedback) likely contribute to this expanded distribution. Upcoming observations should be able to detect these baryons.
机译：对星系团的观察表明，它们所包含的重子（气体加恒星）少于宇宙中的重子。对于最庞大的星团，这种“缺失的重子”难题尤其令人惊讶，它们有望代表宇宙的宇宙物质含量（重子和暗物质）。在这里，我们表明，重子实际上可能没有从簇中消失，而是延伸到比通常观察到的更大的半径。通常在簇的中心区域（病毒半径的-0.5）观察到重子缺乏。但是，观察到的气体密度分布图明显比质量密度分布图浅，这意味着气体比质量分布更多，并且气体分数随半径增加。我们使用观测到的气体和团簇的密度分布来推断所测得的重子分数随半径和团簇质量的函数。我们发现，对于〜5×10〜（13）h_（72）〜（-1）W_☉以上的所有群和星团，重子分数都达到了接近病毒半径的宇宙值。这表明重子并不缺少，它们只是位于簇的郊区。加热过程（例如团簇内气体的冲击加热，超新星和活跃银河核反馈）可能有助于这种扩展的分布。即将出现的观测结果应该能够检测到这些重子。

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  • 作者

    Bilhuda Rasheed; Neta Bahcall; Paul Bode;

  • 作者单位

    Department of Astrophysical Sciences, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544;

    Department of Astrophysical Sciences, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544;

    Department of Astrophysical Sciences, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544;

  • 收录信息 美国《科学引文索引》(SCI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    cosmology; hot intracluster gas;

    机译：宇宙学集群内热气;

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