Mapping the Cosmic-Ray Ionization Rate in the Solar Neighborhood

SFB Colloquium
Dr. Nick Indriolo
SCHEDULED
Johns Hopkins University, Baltimore

Chemical complexity in the molecular interstellar medium (ISM) is driven by fast ion-molecule reactions. This network of chemical reactions requires a source of ionization, and as molecular gas is generally well-shielded from ionizing UV photons, cosmic rays provide the dominant source of ionization in such environments. The impact of cosmic rays on atomic and molecular hydrogen is parameterized as the cosmic-ray ionization rate (CRIR; number of ionizations per atom/molecule per unit time), which serves as an important input variable in astrochemical modeling. Our understanding of cosmic rays in both diffuse and dense gas has vastly improved over the past decade as more detailed chemical models have been developed, and as more sensitive observations of molecules that respond to the CRIR have been made. The recent creation of 3D dust maps using Gaia differential extinction measurements allows, for the first time, ionization rates inferred from observations of molecular absorption lines to be assigned to a physical location in the nearby Galaxy. By combining this information we are beginning to build the first map of the CRIR in the solar neighborhood. I will discuss our ongoing work on this project, and how we can use such a map to better understand cosmic-ray acceleration and propagation.

XRISM's High-Resolution X-ray Spectroscopy: Early Results on Galaxy Cluster Dynamics

Main Colloquium
Prof. Naomi Ota
SCHEDULED
Nara Women’s University

The XRISM satellite, launched in 2023, is the successor to Hitomi and marks a major step forward in high-resolution X-ray spectroscopy. Equipped with the microcalorimeter spectrometer Resolve, XRISM enables precise measurements of gas motions and turbulence in galaxy clusters. In this talk, I will present the initial results from XRISM observations of the A2029 galaxy cluster, highlighting gas dynamics in the cluster core and the role of non-thermal pressure in the outer regions. I will also discuss future prospects, including upcoming observational strategies and implications for galaxy cluster studies.