AKARI 90微米全天巡天的时间轴分析和小波多尺度分析
Timeline analysis and wavelet multiscale analysis of the AKARI All-Sky Survey at 90 micron
摘要：
我们提出了一个仔细的分析AKARI全天巡天在WIDE-S 90 $μ$ m波段的北极（NEP）附近的点源探测极限。时间轴分析用于检测IRAS源，然后导出转换因子以将峰值时间轴信号转换为源的内插90 $μ$ m通量。结合稳健的噪声测量，对于单个探测器行，在S/N $>5$处的点源通量探测极限为$1.1\pm0.1$ Jy，其对应于调查的点源探测极限$\sim$ 0.4 Jy。小波变换提供了时间序列数据（TSD）的多尺度表示。我们计算TSD的连续小波变换，然后搜索被认为是潜在的源检测的重要小波系数。为了区分真实源与虚假或移动对象，仅选择具有确认的源。在我们的多尺度分析中，在点源尺度上，上述$4σ$选择的IRAS源可以被识别为唯一的真实源。利用小波变换和小波功率谱等值线图研究了时间轴分析中探测到的非红外辐射源与卷云辐射之间的相关性。结果表明，非IRAS源最有可能是由过大的噪声在大范围的空间尺度，而不是真正的扩展结构，如卷云。
英文摘要：
We present a careful analysis of the point source detection limit of the AKARI All-Sky Survey in the WIDE-S 90 $μ$m band near the North Ecliptic Pole (NEP). Timeline Analysis is used to detect IRAS sources and then a conversion factor is derived to transform the peak timeline signal to the interpolated 90 $μ$m flux of a source. Combined with a robust noise measurement, the point source flux detection limit at S/N $>5$ for a single detector row is $1.1\pm0.1$ Jy which corresponds to a point source detection limit of the survey of $\sim$0.4 Jy. Wavelet transform offers a multiscale representation of the Time Series Data (TSD). We calculate the continuous wavelet transform of the TSD and then search for significant wavelet coefficients considered as potential source detections. To discriminate real sources from spurious or moving objects, only sources with confirmation are selected. In our multiscale analysis, IRAS sources selected above $4σ$ can be identified as the only real sources at the Point Source Scales. We also investigate the correlation between the non-IRAS sources detected in Timeline Analysis and cirrus emission using wavelet transform and contour plots of wavelet power spectrum. It is shown that the non-IRAS sources are most likely to be caused by excessive noise over a large range of spatial scales rather than real extended structures such as cirrus clouds.
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