Caltech/IPAC Lunch Seminar
Deb Pathak (OSU)
Dusty and Over-Pressured: Stellar Feedback from Normal Star-Forming Disks to Extreme Starburst Environments
The balance between stellar feedback pressures (including radiation, warm ionized gas pressure, and stellar winds), ambient ISM pressure, and self-gravity of star-forming regions controls the rate at which molecular clouds are disrupted and sets the efficiency of star-formation and gas clearing. Using multi-wavelength data (JWST, HST, MUSE, ALMA, VLA, and MeerKAT) from the PHANGS (Physics at High Angular resolution in Nearby GalaxieS) survey, I'll show recent measurements of pre-supernova stellar feedback pressures, self-gravity, and the dynamical state of ~18,000 star-forming regions in 19 nearby star-forming spiral galaxies. We find that ionized gas pressure dominates over radiation pressure and drives HII region expansion, while the local environment sets whether regions are over-pressured and expanding. I will then show new results from the GOALS (Great Observatories All-sky LIRG Survey) collaboration at IPAC, comparing feedback in normal star-forming galaxies against the dusty, highly turbulent ISM in extreme starburst environments. We present the first measurements of stellar feedback pressures associated with ~1,600 young clusters in the nearest Luminous Infrared Galaxy (LIRG), NGC 3256, a late-stage merger at 37 Mpc, using high-resolution JWST, HST, MUSE, and ALMA data. In this dusty merger, we measure feedback pressures that are ~2 orders of magnitude higher than in normal star-forming disks, and radiation pressure (from both UV and IR photons) dominates over ionized gas pressure. We measure turbulent gas pressure and disk dynamical equilibrium pressure, and find high turbulent pressures, indicating the ISM is likely not confined to a disk. We compare the total stellar feedback pressures to the external ISM pressure and find that while clusters in the densest regions are pressure-confined, most clusters are over-pressured relative to their turbulent surroundings and are likely expanding. By bridging normal and extreme star-forming environments, our measurements have direct implications for both the dynamical evolution of star-forming regions across environments, and the efficiency of stellar feedback in ionizing and clearing cold gas before the onset of supernovae, shaping the phase and structure of the multi-scale ISM.
Jayke Nguyen (UCSD)
Finding Hidden Planets With Precision Aperture Masking Interferometry on JWST
Aperture masking interferometry (AMI) is a powerful high contrast direct imaging technique enabling detections at angular separations beyond the typical λ/D diffraction limit. Combining that with the extremely stable environment of JWST, a new regime of precision AMI is possible. Post-launch, JWST AMI was limited by detector systematics (such as the brighter-fatter effect) and aberrations originating from optical telescope element (OTE) limiting its sensitivity. However, a new pipeline, AMIGO, has recently shown significant improvements in forward modeling the full optical system from photons-to-pixels, allowing us to reach photon-noise limited contrasts of ~1e-4 at sub-λ/D angular resolution. Currently, we are applying AMIGO to reduce a backlog of archival JWST AMI data originally collected under GTO and GO programs, but unable to be reduced to their full potential until now. The breadth of AMI data and robustness of AMIGO may also eventually allow us to perform calibrator-free interferometry, reducing required observing time by 50%. By unlocking the full precision of JWST AMI, these archival observations may reveal new planetary companions at solar system scales while establishing a foundation for future JWST interferometric imaging. This study also has design implications for HWO, where the extreme contrast requirements needed to image an Earth-like planet around a Sun-like star will rely on engineered observatory stability and post-processing with forward modeling.