Principal components in active galactic nuclei variability data and the estimation of the flux contributions from different components |
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| Authors: | Chris Koen Fred Lombard |
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| Institution: | South African Astronomical Observatory, PO Box 9, Observatory 7935, Cape, South Africa;Department of Mathematics and Statistics, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa |
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| Abstract: | It has been found that the near-infrared flux variations of Seyfert galaxies satisfy relations of the form Fi ≈α i j +β i j Fj , where Fi , Fj are the fluxes in filters i and j ; and α i , j , β i , j are constants. These relations have been used to estimate the constant contributions of the non-variable underlying galaxies. The paper attempts a formal treatment of the estimation procedure, allowing for the possible presence of a third component, namely non-variable hot dust. In an analysis of a sample of 38 Seyfert galaxies, inclusion of the hot dust component improves the model fit in approximately half the cases. All derived dust temperatures are below 300 K, in the range 540–860 K or above 1300 K. A noteworthy feature is the estimation of confidence intervals for the component contributions: this is achieved by bootstrapping. It is also pointed out that the model implies that such data could be fruitfully analysed in terms of principal components. |
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| Keywords: | methods: data analysis methods: statistical galaxies: active |
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