MAGNETIC FIELDS AND STAR FORMATION IN SPIRAL GALAXIES

MAGNETIC FIELDS AND STAR FORMATION IN SPIRAL GALAXIES
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螺旋星系中的磁场和恒星形成

DOI：
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发表时间：
2008
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通讯作者：
M. Krause
M. Krause
中科院分区：
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文献类型：
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作者：
M. Krause

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本文总结了射电连续谱和偏振观测的主要结果，并在不同形态类型、倾角和星星形成率（SFR）的星系样本中，对正面和侧面旋涡星系的磁场强度和大尺度图案进行了比较。我们发现，低SFR的星系有较高的热分数/较小的同步辐射分数比那些正常或高SFR。采用均分模型，我们得出结论，非热无线电发射和总磁场强度与SFR非线性增长，而规则磁场强度似乎不依赖于SFR。我们还研究了大倾斜（边缘）星系的磁场结构和盘厚度。我们发现，在四个星系，尽管他们不同的无线电外观-的垂直尺度高度，薄和厚盘/晕，大约相等（0.3/1.8千秒差距在4.75千兆赫），独立于他们不同的SFR。这意味着所有这些星系都有一个星系风，其中宇宙线的整体速度（CR）由星系盘内的总场强决定。我们样本中的星系也显示出类似的大尺度磁场配置，平行于中平面，X形远离盘平面，独立于哈勃类型和盘中的SFR。因此，我们得出结论，也大规模的磁场图案不依赖于SFR的量。
The main observational results from radio continuum and polarization observations about the magnetic field strength and large-scale pattern for face-on and edge-on spiral galaxies are summarized and compared within our sample of galaxies of different morphological types, inclinations, and star formation rates (SFR). We found that galaxies with low SFR have higher thermal fractions/ smaller synchrotron fractions than those with normal or high SFR. Adopting an equipartition model, we conclude that the nonthermal radio emission and the total magnetic field strength grow nonlinearly with SFR, while the regular magnetic field strength does not seem to depend on SFR. We also studied the magnetic field structure and disk thicknesses in highly inclined (edge-on) galaxies. We found in four galaxies that -despite their different radio appearance- the vertical scale heights for both, the thin and thick disk/halo, are about equal (0.3/1.8 kpc at 4.75 GHz), independently of their different SFR. This implies that all these galaxies host a galactic wind, in which the bulk velocity of the cosmic rays (CR) is determined by the total field strength within the galactic disk. The galaxies in our sample also show a similar large-scale magnetic field configuration, parallel to the midplane and X-shaped further away from the disk plane, independent of Hubble type and SFR in the disk. Hence we conclude that also the large-scale magnetic field pattern does not depend on the amount of SFR.