X-ray spectroscopy in the microcalorimeter era III: line formation under Case A, Case B, Case C, and Case D in H- and He-like iron for a photoionized cloud

Abstract

Future microcalorimeter X-ray observations will resolve spectral features in unmatched detail. Understanding the line formation processes in the X-rays deserves much attention. The purpose of this paper is to discuss such processes in the presence of a photoionizing source. Line formation processes in one and two-electron species are broadly categorized into four cases. Case A occurs when the Lyman line optical depths are very small and photoexcitation does not occur. Line photons escape the cloud without any scattering. Case B occurs when the Lyman-line optical depths are large enough for photons to undergo multiple scatterings. Case C occurs when a broadband continuum source strikes an optically thin cloud. The Lyman lines are enhanced by induced radiative excitation of the atoms/ions by continuum photons, also known as continuum pumping. A fourth less-studied scenario, where the Case B spectrum is enhanced by continuum pumping, is called Case D. Here, we establish the mathematical foundation of Cases A, B, C, and D in an irradiated cloud with Cloudy. We also show the total X-ray emission spectrum for all four cases within the energy range 0.1 - 10 keV at the resolving power of XRISM around 6 keV. Additionally, we show that a combined effect of electron scattering and partial blockage of continuum pumping reduces the resonance line intensities. Such reduction increases with column density and can serve as an important tool to measure the column density/optical depth of the cloud.

arXiv commentaccepted for publication in ApJ, comments are welcome

References in corpus (21)

• The Quiescent Intracluster Medium in the Core of the Perseus Cluster
• Photoionization Modeling and the K Lines of Iron
• XMM-Newton Reflection Grating Spectrometer Observations of Discrete Soft-X-ray Emission Features from NGC 1068
• X-ray Spectral Survey with XMM--Newton of a Complete Sample of Nearby Seyfert Galaxies
• On the origin of soft X-rays in obscured AGN: answers from high-resolution spectroscopy with XMM-Newton
• Iron and Nickel Line Diagnostics for the Galactic Center Diffuse Emission
• Nebular spectroscopy: A guide on H II regions and planetary nebulae
• Atomic data and spectral modeling constraints from high-resolution X-ray observations of the Perseus cluster with Hitomi
• Resolving the Composite Fe K-alpha Emission Line in the Galactic Black Hole Cygnus X-1 with Chandra
• A Chandra survey of fluorescence Fe lines in X-ray Binaries at high resolution
• Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system. I. The non-dip spectrum in the low/hard state
• The XMM-Newton view of Mrk3 and IXO30
• Measurements of resonant scattering in the Perseus cluster core with Hitomi SXS
• PPAK Integral Field Spectroscopy survey of the Orion Nebula: Data Release
• The ultracool dwarf DENIS-P J104814.7-395606. Chromospheres and coronae at the low-mass end of the main-sequence
• Revisiting He-like X-ray Emission Line Plasma Diagnostics
• Fluorescent excitation of Balmer lines in gaseous nebulae: case D
• Anatomy of the AGN in NGC 5548 IX. Photoionized emission features in the soft X-ray spectra
• X-ray spectroscopy in the microcalorimeter era I: Effects of Fe XXIV Resonance Auger Destruction on Fe XXV K$\alpha$ spectra
• Iron K-alpha Fluorescent Line Profiles from Spiral Accretion Flows in AGNs
• X-ray spectroscopy in the microcalorimeter era II: A new Diagnostic on Column Density from the Case A to B Transition in H- and He-like Iron

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