Special Talk

• Special Talks

  Speaker: Logan Jones (STScI)
  Title: Pinwheeling PAHs: A JWST Tour of M101 and its Interstellar Medium
  Abstract: At metallicities below 0.2x solar, the abundance of PAHs relative to total dust mass drops precipitously, with differences in shielding, ISM density, UV field strength, and grain growth and destruction and mechanisms all proposed to cause this decline. With an exquisite array of ancillary data and a dramatic radial metallicity gradient, the nearby, massive spiral galaxy M101 provides a controlled, single-galaxy laboratory for untangling the effects of local properties on PAH feature variations. Here I present a preliminary look at the results of a comprehensive imaging program with JWST/NIRCam and MIRI in 6 fields across M101 that span >1 dex in metallicity, neutral and ionized gas density, and UV field strength. With ~3500 high S/N PAH measurements (at a binned GALEX-like resolution of 2”), we can remove confounding variables by examining how PAH strengths and ratios vary with just one parameter (e.g., metallicity) while others are held fixed. I show preliminary feature ratio maps across our 6 fields, along with semi-quantitative results relating emission from PAHs, warm dust, and ionized gas. 

  Speaker: Andrew Fox (STScI)
  Title: Dark Matter Minihalos and M94 Cloud-9
  Abstract: A cornerstone prediction of the ΛCDM model is the existence of gas-filled starless dark matter halos on sub-galactic mass scales. Simulations give testable predictions for the H I properties of such starless halos. In 2023 the FAST telescope discovered a compact H I cloud (Cloud-9) near the nearby spiral galaxy M94. Follow-up observations with the VLA and GBT confirmed the cloud and the refined its properties. Cloud-9 is compact (1.4 kpc), dynamically cold (H I line width of 12 km/s), non-rotating, and fairly massive (H I mass of 10^6 solar masses). I will discuss an HST/ACS program led by Rachael Beaton, Gagandeep Anand, and myself that ruled out the presence of a dwarf galaxy down to 10^4 solar masses with 99.5% confidence. The non-detection of a stellar counterpart reinforces the interpretation that Cloud-9 is the first observed example of a starless dark-matter halo (a.k.a. RELHIC). Future studies of a larger population of such starless halos will allow for the determination of fundamental dark matter halo properties.

  Speaker: Leah Hustak (STScI)
  Title: From Data to Dimension: Visualizing the Pillars of Creation in 3D
  Abstract: Through the observation of the Pillars of Creation by Hubble in visible light and the later observations by Webb in infrared light, a more complete picture of the pillars’ structure was formed. A visualization called “The Pillars of Creation: A 3D Multiwavelength Exploration” was produced for NASA by STScI and released as a product of the AstroViz Project of NASA's Universe of Learning, combining observations by both telescopes to help viewers form a mental model of the pillars. The process of creating the visualization challenged the small team at STScI to think about form in multiple wavelengths and pushed them to create new workflows for 3D modeling, texturing, rendering, and compositing. The 3D visualization of the Pillars of Creation provides an example of what is possible when data is available in multiple wavelengths of the same structure, how that data can clarify our mental models, and points to the possibilities future missions could provide in broadening our understanding of structures in the universe.