PCA of PCA: Principal Component Analysis of Partial Covering Absorption in NGC 1365

Abstract

We analyse 400 ks of XMM-Newton data on the active galactic nucleus NGC 1365 using principal component analysis (PCA) to identify model independent spectral components. We find two significant components and demonstrate that they are qualitatively different from those found in MCG?6-30-15 using the same method. As the variability in NGC 1365 is known to be due to changes in the parameters of a partial covering neutral absorber, this shows that the same mechanism cannot be the driver of variability in MCG-6-30-15. By examining intervals where the spectrum shows relatively low absorption we separate the effects of intrinsic source variability, including signatures of relativistic reflection, from variations in the intervening absorption. We simulate the principal components produced by different physical variations, and show that PCA provides a clear distinction between absorption and reflection as the drivers of variability in AGN spectra. The simulations are shown to reproduce the PCA spectra of both NGC 1365 and MCG-6-30-15, and further demonstrate that the dominant cause of spectral variability in these two sources requires a qualitatively different mechanism.

8 pages, 10 figures. Accepted for publication in MNRAS

References in corpus (4)

• On why the Iron K-shell absorption in AGN is not a signature of the local Warm/Hot Intergalactic Medium
• An absorption origin for the X-ray spectral variability of MCG-6-30-15
• XMM-Newton study of the complex and variable spectrum of NGC 4051
• The variable X-ray spectrum of Markarian 766 - I. Principal components analysis

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• Relativistic Reflection Modeling in AGN and Related Variability from PCA: A Brief Review
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