The underlying theme of my research is to understand the physical evolution of interstellar metals and the life cycle of dust: from its nuclear reactive origins to planets. Explaining the prevalence of dust in the Universe as well as its influence on astrophysical processes requires understanding the micro-properties of dust – its mineralogical composition, size, and shape distribution – which informs its origin and fate.
X-ray absorption spectroscopy and X-ray imaging of dust scattering halos provides a treasure trove of information about dust mineralogy, size, and position in space. This wavelength regime is particularly useful for answering astromineralogy because one can distinguish between the gas and solid phases of interstellar metals with X-ray absorption spectroscopy, making direct measurement of abundances feasible. Astromineralogy is a current frontier of X-ray astrophysics, and major breakthroughs are expected with the advent of X-ray IFU spectroscopy that will come available on XRISM and Athena.
With high resolution X-ray spectroscopy of current and future telescopes, we can answer the following questions:
- What is the X-ray signature of solid-phase Oxygen? The most advanced theoretical cross-sections for atomic oxygen are capable of fitting X-ray absorption spectra with no residual features.
- What fraction of diffuse interstellar dust is crystalline? How does this fit with the picture of infrared emission from crystalline and amorphous silicates?
- How does interstellar iron get incorporated into dust? Determining the iron fraction taken up in silicates or nanoparticles is important for understanding dust processing by supernovae and the ISM.
- What is the absolute abundance of interstellar metals? By differentiating between the solid and gas phase, X-ray observations are capable of measuring depletion in the ISM without assuming and abundance table.
- Answering these questions requires fully accounting for the effects of scattering, absorption, and attenuation of X-ray light by interstellar dust (upper right, from Corrales et al., 2016).
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