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arXiv 1611.01705astro-ph.GA
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射电频谱能量分布和Galerkin星形成率定标

The Radio Spectral Energy Distribution and Star Formation Rate Calibration in Galaxies

F. S. Tabatabaei, E. Schinnerer, M. Krause, G. Dumas, S. Meidt, R. Beck, A. Damas-Segovia, E. J. Murphy, D. D. Mulcahy, B. Groves, A. Bolatto, D. Dale, M. Galam… 展开作者

F. S. Tabatabaei, E. Schinnerer, M. Krause, G. Dumas, S. Meidt, R. Beck, A. Damas-Segovia, E. J. Murphy, D. D. Mulcahy, B. Groves, A. Bolatto, D. Dale, M. Galametz, K. Sandstrom, M. Boquien, D. Calzetti, R. C. Kennicutt, L. K. Hunt, I. De Looze, E. W. Pellegrini

摘要:

我们研究的光谱能量分布(SED)的无线电连续辐射从金鱼样本附近的星系,以了解这种发射的能量和起源。Effelsberg在1.4GHz,4.8GHz,8.5GHz和10.5GHz的多波长观测与存档数据相结合,使我们能够第一次确定中射电连续谱(1-10 GHz,MRC)的辐射热光度,并进一步提出与单色射电光度的校准关系。利用贝叶斯马尔可夫链蒙特卡罗(MCMC)技术对1-10 GHz无线电SED进行拟合,得到非热谱指数和热分数f_th的测量值,在1.4 GHz时,平均值α_nt=0.97+-0.16(总谱指数为0.79+-0.15)和f_th= 10% +-9%。MRC光度在样品中的变化超过~3个数量级。热辐射平均占MRC的约23%。我们还比较了热和非热射电示踪剂的恒星形成率的校正诊断,并使用MRC射电光度导出了第一个恒星形成校准关系。非热谱指数随恒星形成率面密度的增大而增大,表明恒星形成反馈对星系宇宙线电子布居的影响。通过比较射电和红外的SED,我们发现,由于恒星形成区的磁场的放大作用,FIR-MRC比会随着恒星形成率的增加而减小。这特别意味着在高红移的比率下降,其中大多数发光/恒星形成星系被检测到。

英文摘要:

We study the spectral energy distribution (SED) of the radio continuum emission from the KINGFISH sample of nearby galaxies to understand the energetics and origin of this emission. Effelsberg multi-wavelength observations at 1.4GHz, 4.8GHz, 8.5GHz, and 10.5GHz combined with archive data allow us, for the first time, to determine the mid-radio continuum (1-10 GHz, MRC) bolometric luminosities and further present calibration relations vs. the monochromatic radio luminosities. The 1-10 GHz radio SED is fitted using a Bayesian Markov Chain Monte Carlo (MCMC) technique leading to measurements for the nonthermal spectral index and the thermal fraction f_th with mean values of alpha_nt=0.97+-0.16 (0.79+-0.15 for the total spectral index) and f_th= 10% +- 9% at 1.4 GHz. The MRC luminosity changes over ~3 orders of magnitude in the sample. The thermal emission is responsible for ~23% of the MRC on average. We also compare the extinction-corrected diagnostics of star formation rate with the thermal and nonthermal radio tracers and derive the first star formation calibration relations using the MRC radio luminosity. The nonthermal spectral index flattens with increasing star formation rate surface density, indicating the effect of the star formation feedback on the cosmic ray electron population in galaxies. Comparing the radio and IR SEDs, we find that the FIR-to-MRC ratio could decrease with star formation rate, due to the amplification of the magnetic fields in star forming regions. This particularly implies a decrease in the ratio at high redshifts, where mostly luminous/star forming galaxies are detected.

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