Multi-wavelength campaign on NGC 7469

Abstract

Aims. Outflows in active galaxies (AGNs) are common, although their launching mechanism, location, and physical impact on the host galaxy remain controversial. We conducted a multi-wavelength six-month campaign to observe the nearby Seyfert galaxy NGC 7469 with several observatories in order to better understand and quantify the outflow in this AGN. Methods. We report on the time-integrated line-resolved X-ray spectrum of NGC 7469 obtained with the Reflection Grating Spectrometer (RGS) on board XMM-Newton. We used the RGS spectrum to discern the many AGN outflow components and applied a global fit to obtain their physical parameters. Results. We find that the AGN wind can be well described by three narrow velocity components at ∼-650,-950, and-2050 km s −1. The RGS clearly resolves the-2050 km s −1 component in C 5+ Ly α, while the-650 km s −1 and-950 km s −1 velocities are blended. Similar velocities (±200 km s −1) are resolved in the UV. The H-equivalent column densities of these components are, respectively, N H ∼ 7 × 10 20 , 2.2 × 10 21 , and 10 20 cm −2 , for a total of ∼3 × 10 21 cm −2 , which was also measured in 2004, indicating the absorber did not significantly change. The-650 km s −1 component shows a broad ionization distribution (−1 log ξ 2, ξ being the ionization parameter in erg s −1 cm). We identify a photo-ionized emission component blue-shifted by ∼-450 km s −1 , somewhat broad (FWHM = 1400 km s −1), and with −1 log ξ 1 erg s −1 cm, which we ascribe to the same outflow that produces the absorption lines. We also find a collisionally ionized component at kT = 0.35 keV that we associate with the circum-nuclear star-formation activity of NGC 7469, as it follows the L FIR /L X ≈ 10 4 relation found in star forming galaxies. The elemental abundance ratios of C, N, Ne, S, and Fe to O in the outflow tend to be between one and two times solar. Preliminary estimates of the absorber distance from the AGN center suggest it is at least a few pc away from the center, but more advanced methods need to be applied in order to obtain better constraints. Conclusions. The complex X-ray spectrum of NGC 7469 demonstrates the richness of high energy phenomena taking place in AGN cores. The subtle spectroscopic differences between the various components require deep, high-resolution observations, such as the present RGS spectrum, if one is to resolve them and perform quantitative plasma diagnostics.

Multi-wavelength campaign on NGC 7469

“…These lines were modeled by Behar et al (2017), and include both photo-driven and collisionally excited lines. They are fixed in our model and are assumed not to be absorbed by the outflow.…”

“…Nonetheless, the best fit favors a covering factor of 1.0 with the 90% confidence interval ranging down to 0.8 when all Behar et al (2017), and fitting is done on the column densities of individual ions. The unidentified features missing in the fit, for example emission at 33Å and absorption at 28Å, are discussed in Behar et al (2017).…”

“…Since constraining the line profile parameters is not the goal of this paper, we fix the ion temperature at 0.1 keV. We then fit only the O +7 Lyα doublet line at the observed wavelength of 19.2Å with the outflow and turbulent velocities thawed and set initially to the values of Behar et al (2017) in order to determine them. Fig.…”

“…The RGS spectra are reduced using 'rgsproc' within the software package SAS 15 1 and combined using the standard RGS command, 'rgscombine'. The reduction is detailed in Behar et al (2017). The spectral fitting in the present paper is done on grouped spectra, re-binned to 20 mÅ (grouping two default SAS bins).…”

“…This is the second paper as part of a multi-wavelength observation campaign on NGC 7469. Behar et al (2017) derived outflow parameters using global fit models of photoionized plasmas. We continue the examination of the XMMNewton RGS spectrum focusing on measurement of the column densities.…”