THE LOCAL RADIO–IR RELATION IN M51
THE LOCAL RADIO–IR RELATION IN M51
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DOI：
10.1088/0004-6256/141/2/41
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发表时间：
2010-11
期刊：
影响因子：
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通讯作者：
G. Dumas;E. Schinnerer;F. Tabatabaei;R. Beck;T. Velusamy;E. Murphy
中科院分区：
文献类型：
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作者：
G. Dumas;E. Schinnerer;F. Tabatabaei;R. Beck;T. Velusamy;E. Murphy
我们使用甚大阵列和 Effelsberg 100 m 望远镜以 1.4 GHz (20 cm)、4.9 GHz (6 cm) 和 8.4 GHz (3.6 cm) 三个频率观测 M51，以获得附近螺旋星系最高质量的射电连续谱图像。这些无线电数据与去卷积的 Spitzer IRAC 8 μm 和 MIPS 24 μm 图像相结合，以搜索和研究无线电-红外相关性的局部变化。利用小波分解，我们比较了 200 pc 和 30 kpc 之间的空间尺度上无线电和红外发射的分布。我们表明射电-红外相关性在整个银盘上并不均匀。它呈现出与各种星系结构相对应的具有局部极值的复杂行为，例如H ii区域、旋臂和臂间细丝的复合体，表明热和非热射电发射的贡献是环境的强函数。特别是，24 μm和20 cm发射的关系在旋臂内和整个星系范围内呈现线性关系，而在旋臂间和外部区域以及内部区域则偏离线性，并具有两种不同的行为：旋臂间和外部区域是亚线性的，而在中心3.5 kpc区域是超线性的。我们的分析表明，射电/红外相关性的变化反映了旋臂和臂间区域之间星际介质特性的变化。旋臂中良好的相关性意味着 24 μm 和 20 cm 正在追踪最近的恒星形成，而尘埃不透明度的变化、“卷云”对红外发射的贡献和/或磁场强度与气体密度之间的关系可以解释旋臂间、外部和内部区域中发现的不同关系。
We observed M51 at three frequencies, 1.4 GHz (20 cm), 4.9 GHz (6 cm), and 8.4 GHz (3.6 cm), with the Very Large Array and the Effelsberg 100 m telescope to obtain the highest quality radio continuum images of a nearby spiral galaxy. These radio data were combined with deconvolved Spitzer IRAC 8 μm and MIPS 24 μm images to search for and investigate local changes in the radio–IR correlation. Utilizing wavelet decomposition, we compare the distribution of the radio and IR emission on spatial scales between 200 pc and 30 kpc. We show that the radio–IR correlation is not uniform across the galactic disk. It presents a complex behavior with local extrema corresponding to various galactic structures, such as complexes of H ii regions, spiral arms, and interarm filaments, indicating that the contribution of the thermal and non-thermal radio emission is a strong function of environment. In particular, the relation of the 24 μm and 20 cm emission presents a linear relation within the spiral arms and globally over the galaxy, while it deviates from linearity in the interarm and outer regions as well in the inner region, with two different behaviors: it is sublinear in the interarm and outer region and overlinear in the central 3.5 kpc. Our analysis suggests that the changes in the radio/IR correlation reflect variations of interstellar medium properties between spiral arms and interarm region. The good correlation in the spiral arms implies that 24 μm and 20 cm are tracing recent star formation, while a change in the dust opacity, “Cirrus” contribution to the IR emission and/or the relation between the magnetic field strength and the gas density can explain the different relations found in the interarm, outer, and inner regions.