Research

Astromineralogy          

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).

Links to papers: 

http://adsabs.harvard.edu/abs/2016MNRAS.458.1345C

http://cxc.harvard.edu/newsletters/news_23/newsletter23.pdf

Galactic Center            

X-ray datasets are information-rich, a fact that has guided my interest in applying cutting edge statistical techniques to modern problems in observational astrophysics. My research on dust scattering requires attention to calibration details and the statistics of X-ray photon counting. 

I apply my Chandra data expertise to study Sgr A*, the supermassive black hole at the center of our Milky Way. The quiescent emission from Sgr A* is surprisingly dim, and is easily outshined by nearby objects. I developed observational techniques to extract and model the low signal-to-noise quiescent spectrum of Sgr A*, made possible by the Chandra Galactic Center X-ray Visionary Project. 

Earth’s position near the outskirts of the Milky Way means that the GC is obscured by a particularly large amount of dust and gas.  The dust scattering halos around compact objects in the dense GC environment cause significant blurring, casting a fog over the heart of our Galaxy.  By using X-ray flares from GC compact objects to study the foreground ISM, I seek to measure and correct images of Sgr A* for the effects of dust blurring.

Links to papers:

https://ui.adsabs.harvard.edu/abs/2020ApJ…891…71C/abstract

https://ui.adsabs.harvard.edu/abs/2017ApJ…839…76C/abstract

Exoplanets from a High Energy perspective                     

New Research