Radio to infrared spectra of late-type galaxies with Planck and Wilkinson Microwave Anisotropy Probe data
Radio to infrared spectra of late-type galaxies with Planck and Wilkinson Microwave Anisotropy Probe data
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使用普朗克和威尔金森微波各向异性探测器数据的晚型星系的射电到红外光谱
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发表时间：
2011
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通讯作者：
R. Beswick
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作者：
M. Peel;C. Dickinson;R. Davies;D. Clements;R. Beswick
我们使用普朗克早期发布的紧凑型源目录与威尔金森微波各向异性探测器 (WMAP) 和其他档案测量相结合，构建了三个附近尘埃恒星形成星系的连续谱：Messier 82、NGC 253 和 NGC 4945。我们使用简单同步加速器、游离游离和热尘埃模型的组合对光谱进行最小二乘拟合，并寻找异常微波发射的证据（美洲）。我们发现所有三个星系的射电频谱都与陡频谱同步加速器发射一致，需要大量的自由发射来解释 30-150 GHz 频率范围内的普朗克和 WMAP 数据点。这使得基于自由发射的恒星形成速率与非热发射的恒星形成速率更加一致。我们对这些星系中 AME 的存在进行了限制，发现它低于基于银河系远红外与 AME 比率的预期。尽管如此，NGC 4945 的频谱形状暗示存在峰值约为 30 GHz 的 AME。未来的普朗克数据将使我们更仔细地观察这些星系，并将分析扩展到更多的星系。
We use the Planck Early Release Compact Source Catalogue combined with Wilkinson Microwave Anisotropy Probe (WMAP) and other archival measurements to construct continuum spectra of three nearby dusty star-forming galaxies: Messier 82, NGC 253 and NGC 4945. We carry out a least-squares fit to the spectra using a combination of simple synchrotron, free-free and thermal dust models, and look for evidence of anomalous microwave emission (AME). We find that the radio spectra of all three galaxies are consistent with steep spectrum synchrotron emission, with a significant amount of free-free emission required to explain the Planck and WMAP data points in the frequency range 30-150 GHz. This brings the star formation rate based on free-free emission into better agreement with that from the non-thermal emission. We place limits on the presence of AME in these galaxies, finding that it is lower than expectations based on the ratio of far-infrared to AME from the Galaxy. Nevertheless, the shape of the spectrum of NGC 4945 hints at the presence of AME with a peak around 30 GHz. Future Planck data will let us look more closely at these galaxies, as well as to extend the analysis to many more galaxies.