Determining the absolute chemical abundance of nitrogen and sulfur in the quasar outflow of 3C298

TL;DR

This study analyzes the chemical composition and physical conditions of the quasar outflow in 3C298 using archival HST data, revealing that metallicity varies with the assumed spectral energy distribution and emphasizing the importance of SED choice.

Contribution

It provides the first detailed determination of nitrogen and sulfur abundances in 3C298's outflow, highlighting the impact of different SED models on abundance estimates.

Findings

Nitrogen and sulfur abundances range from sub-solar to super-solar depending on the SED used.

Electron density of the outflow is estimated to be greater than 10^3.3 cm^-3.

Outflow distance potentially extends up to 2.8 kpc.

Abstract

Context. Quasar outflows are key players in the feedback processes that influence the evolution of galaxies and the intergalactic medium. The chemical abundance of these outflows provides crucial insights into their origin and impact. Aims. To determine the absolute abundances of nitrogen and sulfur and the physical conditions of the outflow seen in quasar 3C298. Methods. We analyze archival spectral data from the Hubble Space Telescope (HST) for 3C298. We measure Ionic column densities from the absorption troughs and compare the results to photoionization predictions made by the Cloudy code for three different spectral energy distributions (SED), including MF87, UVsoft, and HE0238 SEDs. We also calculate the ionic column densities of excited and ground states of N iii to estimate the electron number density and location of the outflow using the Chianti atomic database. Results. The MF87, UVsoft, and HE0238 SEDs yield nitrogen and sulfur abundances at super-solar, solar, and sub-solar values, respectively, with a spread of 0.4 to 3 times solar. Additionally, we determined an electron number density of log(ne) greater than 3.3 cm-3, with the outflow possibly extending up to a maximum distance of 2.8 kpc. Conclusions. Our results indicate solar metallicity within a 60 percent uncertainty range, driven by variations in the chosen SED and photoionization models. This study underscores the importance of SEDs impact on determining chemical abundances in quasars outflows. These findings highlight the necessity of considering a wider range of possible abundances, spanning from sub solar to super solar values.