From Galaxy to Intergalactic Medium -- the Magnetic Connection in the Age of the Square Kilometre Array

从银河系到星际介质——平方公里阵列时代的磁连接

• 批准号: RGPIN-2021-02456
• 负责人: Irwin, Judith
• 金额: $ 2.04万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=763249
• 关键词: Galaxy; Intergalactic; Medium; Magnetic; Connection

I plan to detect and characterize `deep halos' of galaxies. These are gaseous halos, mainly consisting of cosmic rays and magnetic fields, that surround spiral galaxies.  The way to do this is to target galaxies that are edge-on to the line of sight.  When we look at such galaxies with the human eye, they look like a thin line in the sky because of their edge-on orientation.  Our eyes detect the optical light from stars in the galaxy and stars are mostly confined to a thin, spiral-like disk.  However, when we look at radio wavelengths, we start to see the faint halo emission that surrounds these disks. Radio halos extend so far from the the disk that edge-on galaxies no longer look like a thin line.  In fact, I have already shown (from stacking previous data) that most edge-on spiral galaxies look almost spherical when observed at radio wavelengths.  This is probably the case in the Milky Way as well, although it is harder to see this in our own Galaxy because of our location within it.  But if we could make such a measurement from the position of the Sun, we would likely find that the halo extent upwards(away from the plane where the Sun resides) is greater than the distance from the Sun to the Galactic Center! A deep halo is a halo that extends beyond even what I have described above (beyond about 10 kpc). We have every reason to expect that such halos exist because of our knowledge of magnetic fields and cosmic rays in and around galaxies, yet they have never before been detected.  Data that are already in hand as well as proposed new observations using the Very Large Array in New Mexico and the  MeerKat telescope in South Africa (a precursor to the Square Kilometre Array)  will achieve this goal.  Even halos that are closer in to the galaxy disk can yield their secrets through an analysis of the magnetic field strengths and cosmic ray energies.  Such analyses lead to a clear connection between disks and the intergalactic medium.  Halos and deep halos are similar to what we see around the Earth.  The Earth is surrounded by a magnetic field (the van Allen belts) that is constantly bombarded by cosmic rays from the Sun.  The fields adjust and distort in response to this Solar Wind, but remain intact nevertheless.  For galaxies, I am probing the galactic analog of the van Allen belts.  Sometimes, insights gained from looking at a large system from a bird's eye view can be applied to smaller local systems. Students involved in this process will receive scientific and technical expertise at a high level.  They will take part in `big data' science in an exciting project that pushes the boundaries of current knowledge. They will learn to do accurate image processing using many Tbytes of data.  My previous NSERC program led to four press releases in which Canada is featured internationally. The next step is likely to produce even more.

我计划检测和表征星系的“深光晕”。这些是气态光环，主要由围绕螺旋星系的宇宙射线和磁场组成。这样做的方法是针对视线边缘的星系。当我们用人眼看这样的星系时，它们看起来像是天空中的细线，因为它们的边缘方向。我们的眼睛检测到星系中的恒星的光学光，而恒星大部分仅限于薄的螺旋状盘。但是，当我们查看无线电波长时，我们开始看到这些磁盘周围的微弱的光环发射。无线电光环远离磁盘延伸，边缘星系不再像一条细线。实际上，我已经显示（从堆叠以前的数据中）表明，在无线电波长处观察到大多数边缘螺旋星系几乎是球形的。银河系也可能是这种情况，尽管由于我们在其中的位置，很难在我们自己的银河系中看到这一点。但是，如果我们可以从太阳的位置进行这样的测量，我们可能会发现，光环范围向上（远离太阳居住的平面）大于从太阳到银河系中心的距离！深度光环是一种光环，甚至超出了我上面描述的（大约10 kpc）。有充分的理由可以期望由于我们对星系中及其周围的磁场和宇宙射线的了解，因此存在这种光晕，但从未发现它们。使用新墨西哥州和南非的Meerkat望远镜（平方公里阵列的前身）使用非常大的阵列的新观察结果以及提出的新观察结果将实现这一目标。即使是靠近星系磁盘的光晕也可以通过分析磁场强度和宇宙射线能量来产生其秘密。这样的分析导致磁盘与播层间介质之间的明显联系。光环和深光晕与我们在地球周围看到的相似。地球被一个磁场（范·艾伦节拍）所包围，后者不断被太阳的宇宙射线轰炸。这些田地会根据这款太阳风进行调整和扭曲，但仍然保持完整。对于星系，我正在探测Van Allen Beat的银河类似物。有时，从鸟类视图中查看大型系统获得的见解可以应用于较小的本地系统。参与此过程的学生将获得高水平的科学和技术专长。他们将在一个令人兴奋的项目中参与“大数据”科学，该项目突破了当前知识的界限。他们将学习使用许多数据进行准确的图像处理。我以前的NSERC计划导致了四个新闻稿，其中加拿大在国际上进行了介绍。下一步可能会产生更多。