Journal Article

Timeline analysis and wavelet multiscale analysis of the AKARI All-Sky Survey at 90 μm

Lingyu Wang, Michael Rowan-Robinson, Issei Yamamura, Hiroshi Shibai, Rich Savage, Seb Oliver, Matthew Thomson, Nurur Rahman, Dave Clements, Elysandra Figueredo, Tomotsugu Goto, Sunao Hasegawa, Woong-Seob Jeong, Shuji Matsuura, Thomas G. Müller, Takao Nakagawa, Chris P. Pearson, Stephen Serjeant, Mai Shirahata and Glenn J. White

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 387, issue 2, pages 601-615
Published in print June 2008 | ISSN: 0035-8711
Published online May 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13292.x
Timeline analysis and wavelet multiscale analysis of the AKARI All-Sky Survey at 90 μm

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We present a careful analysis of the point-source detection limit of the AKARI All-Sky Survey in the WIDE-S 90-μm band near the North Ecliptic Pole (NEP). Timeline analysis is used to detect IRAS (Infrared Astronomy Satellite) sources and then a conversion factor is derived to transform the peak timeline signal to the interpolated 90-μm flux of a source. Combined with a robust noise measurement, the point-source flux detection limit at signal-to-noise ratio (S/N) > 5 for a single detector row is 1.1 ± 0.1 Jy which corresponds to a point-source detection limit of the survey of ∼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.

Keywords: methods: data analysis; surveys; infrared: galaxies; infrared: ISM

Journal Article.  6624 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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