On the Iwasawa-Taniguchi effect of radio-quiet AGN

Abstract

Aims. The existence of an anti-correlation between the Equivalent Width (EW) of the neutral narrow core of the iron Kα emission line and the 2-10 keV luminosity (the so-called "X-ray Baldwin" or "Iwasawa-Taniguchi" effect) has been debated in the last years. We aim at testing this claim on the largest catalogue of radio quiet AGN high-quality X-ray spectra ever published. Methods. The final sample comprises 157 objects. We search for a relation of the iron line EW not only with the X-ray luminosity, but also with the Black Hole mass, the Eddington ratio and the cosmological distance. The data presented here were analyzed homogeneously, all spectra are from the same instrument and with high Signal-to-Noise Ratio. Results. A linear censored fit on the EW versus 2-10 keV luminosity is highly significant and yields log(EW Fe ) = (1.73 ± 0.03) + (−0.17 ± 0.03) log(L X,44 ), where EW Fe is the EW of the neutral iron Kα line in eV and L X,44 is the 2-10 keV X-ray luminosity in units of 10 44 erg s −1 . The anti-correlation with the Eddington ratio is also very significant, while no dependence of the iron EW on the BH mass is apparent.

Properties of the integrated spectrum of serendipitous 2XMM catalog sources

“…The normalization of our EW Fe versus L X relation is statistically consistent with that reported by Bianchi et al (2007). To check whether this discrepancy in the slope is due to the 2 extreme points at L X < 10 42 erg s −1 , we removed these points and subsequently performed the linear fits.…”

“…However, the slope of the EW Fe versus L X relation we obtained is steeper than the value reported in previous studies (−0.20 ± 0.03, Iwasawa & Taniguchi 1993;−0.17 ± 0.08, Page et al 2004; −0.17 ± 0.03, Bianchi et al 2007). The normalization of our EW Fe versus L X relation is statistically consistent with that reported by Bianchi et al (2007).…”

“…This trend was confirmed by later ASCA observations of broad iron lines (Nandra et al 1997). In recent years, the existence of the IT effect for the narrow Fe Kα emission lines in type 1 AGNs observed by XMM-Newton and Chandra has been well established (Page et al 2004;Zhou & Wang 2005;Bianchi et al 2007;Wu et al 2009). …”

“…The mean of the slopes and the intercepts derived from the fits of each data set are taken as the "best fit parameters of the linear relation". We obtained the following best fit relation: Bianchi et al (2007). The combined error range on the slope and normalization of the best fit is also shown by dotted lines in the respective colors.…”

X-ray spectral parameters for a sample of 95 active galactic nuclei

“…Dadina 2008, De Rosa et al 2012, Winter et al 2009, Ballantyne, 2014. On the other hand, the effect the decreasing dependence of FeK EW of the luminosity has been claimed (Bianchi et al 2007;Dadina 2008;Page et al 2004, Ricci 2013, Gimenez-Garcia et al, 2015 for the Seyfert1s in the range of 2 10 keV . Recently, Baldwin effect has been reported for Seyfert2s using the Suzaku data (Fukuzawa et al 2011) and both for Suzaku and XMM-Newton data (Ricci et al 2014b and references therein).…”