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

Abstract

Aims. 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 Chandra High Energy Transmission Grating Spectrometer and the XMM-Newton Reflection Grating Spectrometer. Methods. By modeling the continuum with a simple broken power-law and by implementing the new ISMabs X-ray absorption model, we have estimated the total H, O, Ne, and Fe column densities towards the observed sources. Results. We have determined the absorbing material distribution as a function of source distance and galactic latitude-longitude. Conclusions. 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.

Probing the structure of the gas in the Milky Way through X-ray high-resolution spectroscopy

“…Our results for the neutral component are within 35% of the column densities obtained by Gatuzz et al (2016) for those LMXBs that are included in our sample. However, for the warm component we found an average of ≈ 2.5 times their column densities.…”

“…A method commonly used to study the absorption lines due to the different ionic species observed in X-ray spectra is through fitting a Gaussian profile to individual lines. In this way the measurement of the equivalent widths (EWs) allows On the other hand, there have been attempts to model the ISM with physically motivated models, which include ionization equilibrium conditions, to study the physical conditions of the gas directly (Pinto et al 2010(Pinto et al , 2013Gatuzz et al 2016;Nicastro et al 2016a). As has been shown by Gatuzz et al (2016), the use of physical models helps to prevent misidentification of absorption features compared with traditional phenomenological fitting methods.…”

“…In this way the measurement of the equivalent widths (EWs) allows On the other hand, there have been attempts to model the ISM with physically motivated models, which include ionization equilibrium conditions, to study the physical conditions of the gas directly (Pinto et al 2010(Pinto et al , 2013Gatuzz et al 2016;Nicastro et al 2016a). As has been shown by Gatuzz et al (2016), the use of physical models helps to prevent misidentification of absorption features compared with traditional phenomenological fitting methods. For in- stance, using such a physical model Nicastro et al (2016b) concluded that the absorption line located at ∼ 22.275Å, which was previously attributed to the warm-hot intergalactic medium (WHIM), is produced by the O ii Kβ transition associated with the local ISM.…”

What We Learn from the X-Ray Grating Spectra of Nova SMC 2016

“…For each spectrum, the lower panel shows, in linear scale, the residuals, namely the difference between the data and the model. Galactic (usually low mass X-ray binaries, see Gatuzz et al 2016;Gatuzz & Churazov 2018), and extragalactic (AGN, see e.g. Nicastro et al 2016b,a;Gatuzz & Churazov 2018).…”

Photoionization of Ne Atoms and Ne+ Ions Near the K Edge: PrecisionSpectroscopy and Absolute Cross-sections

“…By combining theory and astrophysical observation, e.g., by employing the capabilities of Chandra to measure X-ray absorption by the local interstellar medium, it has been possible to infer accurate wavelengths of inner-shell transitions in atoms and ions in general, as well as for neon and its ions in particular (Juett et al 2006;Yao et al 2009;Liao et al 2013;Gatuzz et al 2015Gatuzz et al , 2016. The main contribution of theory to such joint investigations is to provide cross-sections for photoabsorption of atoms and their ions.…”