Events Daily

Thursday, October 13, 2022

Tracing Gas Ionization in Galaxies
Xihan Ji, University of Kentucky
Event Type: Informal Astro Talk
Time: 11:00 AM - 11:30 AM
Location: 726 Broadway, 940, CCPP Seminar
Abstract: Young massive stars create HII regions and drive them to expand over time through the energetic feedback. Due to the small physical sizes and low expanding velocities of most HII regions, it is difficult to study their dynamical evolution directly. Interestingly, early dynamical models predict that stellar feedback results in a correlation between the metallicity and ionization parameter in HII regions. This correlation provides a unique way to investigate the impact of stellar feedback on small scales using nebular diagnostics. However, previous works derived discrepant correlations from observations. In this talk, I will introduce our solution with a refined calibration method using photoionization models. We applied our method to the HII regions in SDSS-IV MaNGA, and found that the stellar-wind feedback model alone is insufficient to explain the derived correlation. To further understand this issue, I plan to investigate the detailed ionization structures of HII regions using the upcoming surveys on the local ISM.

Broken Symmetries in Living Matter
Nikta Fakhri, Massachusetts Institute of Technology
Event Type: Physics Dept Colloquium
Time: 4:00 PM - 5:30 PM
Location: 726 Broadway, 940, CCPP Seminar
Abstract: Active processes in living systems create a novel class of nonequilibrium matter composed of many interacting components that individually consume energy and collectively generate motion or mechanical stress. In this talk, I will discuss experimental tools and conceptual frameworks we develop to uncover laws governing fluctuations, order, and self-organization in systems in which individual components break time reversal symmetry. I will describe how such frameworks provide powerful insight into dynamics of nonequilibrium living systems across scales, from the emergence of thermodynamic arrow of time to spatiotemporal organization of signaling protein patterns and discovery of odd elasticity.