Multiwavelength Structural Manifestations of Fast Magnetohydrodynamic Density Waves in Spiral Galaxies
Multiwavelength Structural Manifestations of Fast Magnetohydrodynamic Density Waves in Spiral Galaxies
复制标题
螺旋星系中快磁流体动力密度波的多波长结构表现
DOI：
10.1086/338244
复制
发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Z. Fan
中科院分区：
文献类型：
--
作者：
Y. Lou;W. Walsh;J. Han;Z. Fan
在螺旋星系中，恒星盘和磁化星际介质（ISM）在重力作用下动态耦合。这种复合旋转圆盘系统的磁流体动力学（MHD）密度波理论为研究星系结构的大尺度动力学和多波长诊断提供了基本框架。中性氢的H盘通常比盘状星系的光学螺旋图案大，由于带有宽而模糊臂（规则或不规则）的旋涡状拖尾螺旋结构，H盘中的螺旋MHD密度波应该在光学图案内外持续存在。相对论性宇宙射线电子在光学模式之外的零星扩散可能会导致射电连续统臂偶尔延伸到光学螺旋模式上，并与半径更大的H - I螺旋臂相关。我们在此报告了对南部螺旋星系NGC 2997的第一次H I观测，以支持快速MHD密度波（FMDW）的假设，并证实了先前的预测，即在东南象限发现的孤立的极化射电连续臂确实与H I臂的一个广泛部分有关。对于螺旋星系的多波长观测，我们强调了MHD密度波的大尺度磁场在组织各种潜在ISM成分的相关螺旋结构中起关键作用的重要观点。同时，参考ngc1097的环核结构，简要讨论了ngc2997的环核结构性质。
In a spiral galaxy, disks of stars and of magnetized interstellar medium (ISM) are dynamically coupled by gravity. The theory of magnetohydrodynamic (MHD) density waves in such a composite rotating disk system provides a basic framework for studying large-scale dynamics and multiwavelength diagnostics of galactic structures. As swirllike, trailing spiral structures with broad, fuzzy arms (regular or irregular) manifest in neutral hydrogen H I disks that are usually larger than optical spiral patterns in disk galaxies, spiral MHD density waves in H I gas disks should persist within and beyond optical patterns. Sporadic diffusions of relativistic cosmic-ray electrons beyond optical patterns may cause radio continuum arms to occasionally extend across optical spiral patterns and correlate with H I spiral arms at larger radii. We here report the first H I observations of the southern spiral galaxy NGC 2997 to support the fast MHD density wave (FMDW) scenario and to confirm the prior prediction that the isolated, polarized radio continuum arm discovered in the southeast quadrant is indeed associated with a broad segment of the H I arm. For multiwavelength observations of spiral galaxies, we emphasize the important perspective that large-scale magnetic fields of MHD density waves play the key role in organizing correlated spiral structures of the various underlying ISM components. Meanwhile, we briefly discuss the nature of circumnuclear structures of NGC 2997 in reference to those of NGC 1097.