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arXiv 0907.3843astro-ph.CO
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根据WMAP 3年数据在16和33 GHz对河外源的跟踪观测:II -通量密度变化

Follow-up observations at 16 and 33 GHz of extragalactic sources from WMAP 3-year data: II - Flux-density variability

Thomas M. O. Franzen, Matthew L. Davies, Rod D. Davies, Richard J. Davis, Farhan Feroz, Ricardo Genova-Santos, Keith J. B. Grainge, David A. Green, Michael P. H… 展开作者

Thomas M. O. Franzen, Matthew L. Davies, Rod D. Davies, Richard J. Davis, Farhan Feroz, Ricardo Genova-Santos, Keith J. B. Grainge, David A. Green, Michael P. Hobson, Natasha Hurley-Walker, Anthony N. Lasenby, Marcos Lopez-Caniego, Malak Olamaie, Carmen P. Padilla-Torres, Guy G. Pooley, Rafael Rebolo, Carmen Rodriguez-Gonzalvez, Richard D. E. Saunders, Anna M. M. Scaife, Paul F. Scott, Timothy W. Shimwell, David J. Titterington, Elizabeth M. Waldram, Robert A. Watson, Jonathan T. L. Zwart

摘要:

利用16 GHz的Arcminute Microkelvin Imager(AMI)和33 GHz的Very Small Array(VSA)对新的河外WMAP点源目录中的源进行后续观测,我们研究了在几个月到大约1.5年的时间尺度内97个源的完整样本中的通量密度变化。我们发现,53%的93个来源,我们有多个观测,是可变的,在99%的置信水平,以上的通量密度校准不确定性约为4%,在16 GHz的;的分数变化超过20%的来源是15%,在16 GHz和20%,在33 GHz。不仅是这种常见的变异性在源物理学的兴趣高频率发生,但在CMB工作中应对源污染的策略必须考虑到这种变异性。没有强有力的证据表明样品的变异性和通量密度之间存在相关性。使用最大似然法,我们计算的相关性在两个频率的变异性在一个子集的来源分类为变量从AMI和VSA数据,并发现皮尔逊积矩相关系数是非常高的(0.955 +/- 0.034)。我们还发现,在16 GHz(0.202 +/- 0.028)的变化程度是非常相似的,在33 GHz(0.224 +/- 0.039)。最后,我们研究了变率和光谱指数α_13.9 ^33.75(其中S与nu^-α成正比)之间的关系,发现可变源(-0.06 +/-0.05)和不变源(0.13 +/-0.04)的光谱指数存在显著差异。

英文摘要:

Using the Arcminute Microkelvin Imager (AMI) at 16 GHz and the Very Small Array (VSA) at 33 GHz to make follow-up observations of sources in the New Extragalactic WMAP Point Source Catalogue, we have investigated the flux-density variability in a complete sample of 97 sources over timescales of a few months to approximately 1.5 years. We find that 53 per cent of the 93 sources, for which we have multiple observations, are variable, at the 99 per cent confidence level, above the flux density calibration uncertainties of approximately 4 per cent at 16 GHz; the fraction of sources having varied by more than 20 per cent is 15 per cent at 16 GHz and 20 per cent at 33 GHz. Not only is this common occurrence of variability at high frequency of interest for source physics, but strategies for coping with source contamination in CMB work must take this variability into account. There is no strong evidence of a correlation between variability and flux density for the sample as a whole. Using a maximum-likelihood method, we calculate the correlation in the variability at the two frequencies in a subset of sources classified as variable from both the AMI and VSA data and find the Pearson product-moment correlation coefficient to be very high (0.955 +/- 0.034). We also find the degree of variability at 16 GHz (0.202 +/- 0.028) to be very similar to that at 33 GHz (0.224 +/- 0.039). Finally, we have investigated the relationship between variability and spectral index, alpha_13.9^33.75 (where S proportional to nu^-alpha), and find a significant difference in the spectral indices of the variable sources (-0.06 +/- 0.05) and non-variable sources (0.13 +/- 0.04).

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