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arXiv 1306.0226astro-ph.CO
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NGC 3044和NGC 4157中617 MHz - $λ$ 850 $μ$ m相关（宇宙射线和冷尘埃）

The 617 MHz - $λ$ 850 $μ$m Correlation (Cosmic Rays and Cold Dust) in NGC 3044 and NGC 4157

Judith A. Irwin, Rupinder S. Brar, D. J. Saikia, Richard N. Henriksen

备注：
19 pages; Figure 1 is included as an associated jpg file. Accepted to mnras
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摘要：

我们给出了NGC 3044和NGC 4157在JCMT的$λ\,450 μ$ m和$λ\,850 μ$ m处的第一张图，以及在GMRT的617 MHz处的第一张图。在NGC 3044的射电连续谱和亚毫米波段以及NGC 4157的射电连续谱中都探测到了高纬度辐射，其中包括几个新的特征。长波长的尘埃光谱需要与两个星系的双温度模型拟合，这意味着冷尘埃的存在。NGC 3044和NGC 4157的尘埃质量分别为$M_d\,=\,1.6\,\times\,10^8 M_\odot$和$M_d\,=\,2.1\,\times\,10^7 M_\odot$，并以冷分量为主。两个星系的617 MHz和$λ\,850 μ$ m辐射之间存在明显的相关性。在NGC 3044的情况下，这意味着非热同步辐射和冷尘埃之间的关系。617 MHz的成分代表了过去$10^{7-8}$年大质量恒星形成的综合，而$λ\,850 μ$ m的发射代表了来自弥漫星际辐射场（ISRF）的加热。617 MHz -$λ\,850 μ$ m的相关性提高时，平滑内核被应用到$λ\,850 μ$ m的数据占CR电子扩散尺度和ISRF光子尘埃的平均自由程之间的差异。NGC 3044的最佳拟合关系是$L_{617_{\rm MHz}}\,\propto\,{L_{850 μ{\rm m}}}^{2.1\,\pm\,0.2}$。如果冷尘埃辐射率的变化主要由尘埃密度的变化决定，而同步辐射取决于磁场强度（气体密度的函数）以及CR电子的产生（根据施密特定律，大质量恒星形成率和密度的函数），那么NGC 3044的预期相关性是$L_{617_{\rm MHz}}\,\propto\,{L_{850 μ{\rm m}}}^{2.2}$，与观测到的相关性一致。

英文摘要：

We present the first maps of NGC 3044 and NGC 4157 at $λ\,450 μ$m and $λ\,850 μ$m from the JCMT as well as the first maps at 617 MHz from the GMRT. High latitude emission has been detected in both the radio continuum and sub-mm for NGC 3044 and in the radio continuum for NGC 4157, including several new features. The dust spectrum at long wavelengths required fitting with a two-temperature model for both galaxies, implying the presence of cold dust. Dust masses are $M_d\,=\,1.6\,\times\,10^8 M_\odot$ and $M_d\,=\,2.1\,\times\,10^7 M_\odot$ for NGC 3044 and NGC 4157, respectively, and are dominated by the cold component. There is a clear correlation between the 617 MHz and $λ\,850 μ$m emission in the two galaxies. In the case of NGC 3044, this implies a relation between the non-thermal synchrotron emission and cold dust. The 617 MHz component represents an integration of massive star formation over the past $10^{7-8}$ yr and the $λ\,850 μ$m emission represents heating from the diffuse interstellar radiation field (ISRF). The 617 MHz -- $λ\,850 μ$m correlation improves when a smoothing kernel is applied to the $λ\,850 μ$m data to account for differences between the CR electron diffusion scale and the mean free path of an ISRF photon to dust. The best-fit relation is $L_{617_{\rm MHz}}\,\propto\,{L_{850 μ{\rm m}}}^{2.1\,\pm\,0.2}$ for NGC 3044. If variations in the cold dust emissivity are dominated by variations in dust density, and the synchrotron emission depends on magnetic field strength (a function of gas density) as well as CR electron generation (a function of massive star formation rate and therefore density via the Schmidt law) then the expected correlation for NGC 3044 is $L_{617_{\rm MHz}}\,\propto\,{L_{850 μ{\rm m}}}^{2.2}$, in agreement with the observed correlation.

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