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Astro Seminar

Rethinking the nature of interstellar dust

Speaker: Brandon Hensley (Princeton)
Date: Wednesday 21 October 2020
Time: 16:00
Venue: Zoom

The highly polarized emission from Galactic dust as seen by the Planck satellite has challenged our basic assumptions about the makeup of interstellar grains. I will first describe the mid-infrared (MIR) extinction features that serve as the 'fingerprints' of the specific materials composing dust. A new determination of the mean Galactic MIR extinction curve using the highly-reddened sightline toward the hypergiant Cyg OB2-12 will be presented, including detection of absorption features from polycyclic aromatic hydrocarbons (PAHs). I will then overview how the polarization properties of grains depend on composition and how recent results from polarimetry are incompatible with the previous generation of dust models. Finally, I will introduce a new model of interstellar dust that posits that the silicate and carbonaceous materials largely reside on the same grains, an idealized mixture we term 'astrodust'. I will demonstrate the compatibility of the astrodust-based model with existing observations and highlight how it can be tested with future data.