Oxygen, neon, and iron X-ray absorption in the local interstellar medium

TL;DR

This study analyzes X-ray spectra from 24 galactic sources to measure interstellar medium absorption, revealing the distribution and ionization state of elements like oxygen, neon, and iron.

Contribution

It introduces the new ISMabs model for X-ray absorption and applies it to estimate element column densities and ionization fractions in the local interstellar medium.

Findings

Cold component dominates ionization state of O, Ne, Fe

Low overall ionization in the local interstellar medium

Absorbing material distribution varies with source distance and position

Abstract

We present a detailed study of X-ray absorption in the local interstellar medium by analyzing the X-ray spectra of 24 galactic sources obtained with the {\it Chandra} High Energy Transmission Grating Spectrometer and the {\it XMM-Newton} Reflection Grating Spectrometer. By modeling the continuum with a simple broken power-law and by implementing the new {\tt ISMabs} X-ray absorption model, we have estimated the total H, O, Ne, and Fe column densities towards the observed sources. We have determined the absorbing material distribution as a function of source distance and galactic latitude--longitude. Direct estimates of the fractions of neutrally, singly, and doubly ionized species of O, Ne, and Fe reveal the dominance of the cold component, thus indicating an overall low degree of ionization. Our results are expected to be sensitive to the model used to describe the continuum in all sources.