Magnetic fields and ionized gas in the local group irregular galaxies IC 10 and NGC 6822
Magnetic fields and ionized gas in the local group irregular galaxies IC 10 and NGC 6822
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本星系群 IC 10 和 NGC 6822 中的磁场和电离气体
DOI：
10.1051/0004-6361:20030628
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发表时间：
2003
影响因子：
6.5
通讯作者：
M. Urbanik
中科院分区：
文献类型：
--
作者：
K. Chyży;J. Knapík;D. Bomans;U. Klein;R. Beck;M. Soida;M. Urbanik
我们利用Eelsberg 100 m射电望远镜在10.45 GHz和4.85 GHz波段对两个本星系群不规则星系IC 10和NGC 6822进行了高灵敏度的星系尺度磁场搜索，并伴有H成像。它们的恒星形成体很小，旋转缓慢。众所周知，IC 10具有非常高的恒星形成活动，类似于蓝色致密矮星，而NGC 6822的整体恒星形成水平较低。尽管目前的恒星形成速率非常不同，但我们的H成像显示在IC 10和NGC 6822中都有一个大的废氢丝和壳网。其中一些延伸到远离星系主体的地方。这两个天体的总发射功率都显示出明亮的峰值，要么在光学强的恒星形成团块（IC 10）的位置，要么在个别的H ii区域或超新星遗迹（NGC 6822）的位置。然而，在这两种情况下，我们都检测到平滑分布的扩展组件。在ic10中，我们发现了明确的证据，表明存在一个不使用的，几乎是随机的磁场，强度为14G，可能是由波动发电机产生的。其中一个发射氢的细丝似乎与增强的磁场有关。我们还重新讨论了ic10的变红及其对距离的影响。在NGC 6822的例子中，除了可能与局部气体压缩有关的一些区域外，我们只发现了非常微弱的非热发射证据。我们在两个星系中都探测到偏振发射的小斑点，这表明是规则场（3G），至少部分与局部压缩现象有关。
We performed a high-sensitivity search for galaxy-scale magnetic fields by radio polarimetry at 10.45 GHz and 4.85 GHz with the Eelsberg 100 m radio telescope, accompanied by H imaging, for the two Local Group irregular galaxies IC 10 and NGC 6822. Their star-forming bodies are small and rotate slowly. IC 10 is known to have a very high star-forming activity, resembling blue compact dwarfs, while NGC 6822 has a low overall star-formation level. Despite very dierent current star formation rates, our H imaging revealed a large web of diuse H filaments and shells in both IC 10 and NGC 6822. Some of them extend far away from the galaxy's main body. The total power emission of both objects shows bright peaks either at the positions of optically strong star-forming clumps (IC 10) or individual H ii regions or supernova remnants (NGC 6822). However, in both cases we detect a smoothly distributed, extended component. In IC 10 we found clear evidence for the presence of a diuse, mostly random magnetic field of '14G strength, probably generated by a fluctuation dynamo. One of the H-emitting filaments appears to be associated with enhanced magnetic fields. We also rediscuss the reddening of IC 10 and its implications for its distance. In the case of NGC 6822 we found only very weak evidence for nonthermal emission, except perhaps for some regions associated with local gas compression. We detect in both galaxies small spots of polarized emission, indicative of regular fields ('3G), at least partly associated with local compressional phenomena.