Exploring the Nuclear Environment of the NLS1 Galaxy Arakelian 564 with XMM-Newton RGS

TL;DR

This study provides a detailed high-resolution X-ray spectral analysis of the NLS1 galaxy Arakelian 564, revealing multiple emission lines and ionized gas phases, and compares its properties with similar objects to understand its nuclear environment.

Contribution

It offers the first detailed characterization of the X-ray spectrum of Arakelian 564, identifying multiple emission lines and ionized gas phases, and proposes a connection between the broad and narrow line regions.

Findings

Identified five significant emission lines with specific velocities.

Detected three phases of photoionized, X-ray absorbing gas.

Found an unusually low velocity outflow in the galaxy.

Abstract

We present an accurate characterisation of the high-resolution X-ray spectrum of the Narrow Line Seyfert 1 galaxy Arakelian 564 and put it in to context with other objects of its type by making a detailed comparison of their spectra. The best fit to the data identifies five significant emission lines at 18.9, 22.1, 24.7, 29.0 and 33.5A due O VIII Ly alpha, O VII(f), N VII Ly alpha, N VI(i) and C VI Ly alpha respectively. These have an RMS velocity of ~1100km/s and a flow velocity of ~-600km/s, except for the O VII(f) emission line, which has a flow velocity consistent with zero. Two separate emitting regions are identified. Three separate phases of photoionized, X-ray absorbing gas are included in the fit with ionization parameters log xi=-0.86, 0.87, 2.56 and column densities N_H=0.89, 2.41, 6.03*10^20cm^-2 respectively. All three phases show this to be an unusually low velocity outflow (-10pm100km/s) for a narrow line Seyfert 1. We present the hypothesis that the BLR is the source of the NLR and warm absorber, and examine optical and UV images from the XMM-Newton Optical Monitor to relate our findings to the characteristics of the host galaxy.