Guest Speaker - Dr. Jessica Sutter, Professor of Astronomy at Whitman College

TUESDAY March 19th

7:00 PM

North Medford High School Planetarium

The gas and dust that fills galaxies, commonly referred to as the interstellar medium (ISM), regulates the formation of stars and determines the future growth of a galaxy. Infrared observations are ideal for studying the ISM, as attenuation caused by dust does not impact these wavelengths as it does UV and optical light. In the near and mid infrared, the emission features of small dust grains known as polycyclic aromatic hydrocarbons (PAHs) dominate galaxy emission, measurements of which can illuminate the PAH population and provide constraints on how the ISM is being heated. In the far-infrared, forbidden fine-structure lines inform us of the cooling efficiency and provide a vital tool for understanding distant galaxies. Specifically, the 158 micron line of singly-ionized carbon has become a popular tool for determining the star-formation rate, molecular gas content, and prevalence of shocks within the ISM. By studying infrared observations of nearby galaxies, we can establish how the properties of the ISM vary across different environments. Comparisons to optical diagnostics and spectral energy distribution fitting can illuminate changes to the star formation efficiency across galaxy disks. Measurements of nearby galaxies also provide the context for high redshift observations. With the first data from the James Webb Space Telescope providing unprecedented spatial resolution and sensitivity, we can now trace the dust in nearby galaxies on scales of tens of parsecs, providing a view of the ISM previously only accessible in the Local Group. Using both new data from JWST and archival data from Herschel and SOFIA, I will discuss the power of infrared measurements in understanding the conditions within the ISM.