Nitrogen X-ray absorption in the local ISM

TL;DR

This study analyzes nitrogen K-edge X-ray absorption in the local interstellar medium using high-resolution spectra from XMM-Newton, revealing phase-dependent column density variations and agreement with UV data.

Contribution

First detailed analysis of nitrogen K-edge absorption in the ISM using high-resolution X-ray spectra, providing insights into different gas phases.

Findings

Cold-warm nitrogen column densities decrease with Galactic latitude.

Hot nitrogen component remains relatively constant across latitudes.

Good agreement between X-ray and UV measurements of nitrogen in the ISM.

Abstract

Nitrogen is one of the most abundant metals in the interstellar medium (ISM), and thus it constitutes an excellent test to study a variety of astrophysical environments, ranging from nova to active galactic nuclei. We present a detailed analysis of the gaseous component of the N K~edge using high-resolution {\it XMM-Newton} spectra of 12 Galactic and 40 extragalactic sources. For each source, we have estimated column densities for {\rm N}~{\sc i}, {\rm N}~{\sc ii}, {\rm N}~{\sc iii}, {\rm N}~{\sc v}, {\rm N}~{\sc vi} and {\rm N}~{\sc vii} ionic species, which trace the cold, warm and hot phases of the local Galactic interstellar medium. We have found that the cold-warm component column densities decrease with the Galactic latitude while the hot component does not. Moreover, the cold column density distribution is in good agreement with UV measurements. This is the first detailed analysis of the nitrogen K-edge absorption due to ISM using high-resolution X-ray spectra.