Determine the density of the LIP and HVIP absorbers in NGC 4051

Determine the hydrogen-equivalent number density nH of the low-ionization phase (LIP) and the high-velocity and high-ionization phase (HVIP) photoionized absorbers in the Narrow-Line Seyfert 1 galaxy NGC 4051, for which neither upper nor lower limits on nH could be obtained from the time-evolving photoionization fit using TEPID.

Background

This paper analyzes two XMM-Newton RGS observations of NGC 4051 and identifies three distinct photoionized absorbers: a low-ionization phase (LIP), a high-ionization phase (HIP), and a high-velocity high-ionization phase (HVIP). While time-evolving photoionization modeling (TEPID) allowed the authors to constrain the density and distance of the HIP due to its non-equilibrium behavior, the LIP and HVIP appeared consistent with photoionization equilibrium or exhibited insufficient variability to enable density constraints.

In time-dependent analyses, measuring nH is crucial to break the degeneracy between density and distance (R) inherent in equilibrium models. Without constraints on nH for the LIP and HVIP, their precise locations and physical conditions remain undetermined, limiting the interpretation of the multi-phase outflow structure in NGC 4051.