Multi-wavelength campaign on NGC 7469. I. The rich 640 ks RGS spectrum

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 C⁵⁺ 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 × 10²⁰, 2.2 × 10²¹, and 10²⁰ cm^-2, for a total of 3 × 10²¹ 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 ≈ 10⁴ 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.