Determining the composition and location of interstellar dust is key to our understanding of stellar nucleosynthesis and the elemental abundances in our galaxy, as well as broader issues such as the…

This federal contract award, with ID 80NSSC19K0571, was made by the Shared Services Center, a civilian agency, to The Trustees of Columbia University in the City of New York. The $347,011.99 grant funds research to analyze high-resolution X-ray photoabsorption spectra of the interstellar medium (ISM) from the Reflection Grating Spectrometer on the X-ray Multi-Mirror Mission Newton spacecraft and the High Energy Transmission Grating Spectrometer on the Chandra X-ray Observatory. This research aims to determine the composition and location of interstellar dust, which is key to understanding stellar nucleosynthesis, elemental abundances in the galaxy, and planetary system formation. The contract does not have a set-aside designation and is set to be completed by March 31, 2023.

Determining the composition and location of interstellar dust is key to our understanding of stellar nucleosynthesis and the elemental abundances in our galaxy, as well as broader issues such as the life cycles of STARS. Knowledge about the composition of the dust grains can also be used to follow their pathway to larger astronomical bodies, enabling US to trace out the formation history of planetary systems. Unfortunately, traditional techniques for deriving elemental depletions onto grains, using optical and ultraviolet (UV) absorption spectra of individual metal ions, suffer from uncertainties introduced by the ionization corrections (i.e., accounting for the unseen ionization states). Additionally, a large, but poorly constrained, fraction of the interstellar FE is locked up in the solid-phase, namely in dust grains which are not detectable in the UV. High resolution x-RAY photoabsorption spectra of the interstellar medium (ISM) is the sole technique that can simultaneously detect metals in all charge states and phases of the ISM. This makes x-RAY observations unique and complementary to ISM studies in the radio, infrared, and UV. We propose to analyze all suitable high resolution x-RAY photoabsortion spectra of the ISM currently available from the reflection grating spectrometer (RGS) on board x-RAY multi-mirror mission newton (XMM-newton), encompassing approximately two dozen different sight lines through the ISM. We will supplement the archival RGS with archival data from high energy transmission grating spectrometer (hetgs) on board the chandra x-RAY observatory.