Speaker
Description
Recent years have seen mounting evidence that the dominant contribution of
Lyman-Continuum photons driving cosmic Reionization has come from hot, massive stars in the first galaxies. How these photons have escaped the shroud of HI in their galaxies of origin to ionize the IGM is still debated and studied intensely. Many mechanisms have been suggested that can create the necessary escape channels, but testing these hypotheses is challenging. It requires mapping the production and escape sites of LyC photons, as well as a mapping of ISM properties on scales spanning from individual HII regions to galaxy-spanning, large scale outflows.
Such studies are not possible to carry out at low redshifts with current
facilities; the only current instrument capable of observing ionizing photons at low redshifts is the Cosmic Origins Spectrograph onboard HST, which has an aperture size of 2.5", limiting the spatial precision of these observations to a few hundred parsec in the nearest known LCEs. At higher redshifts, where the observations of LyC is less technically challenging, the distance becomes the limiting factor to the attainable spatial detail. Ironically, the best prospects for this kind of study are found at cosmological distances, where the probability of strong gravitational lensing is grows large enough to allow us to catch strongly lensed leakers in large enough magnification to enable this challenging kind of study.
In this talk, I will present detailed JWST/NIRCam and NIRSpec Integral Field Spectroscopic observations of physical ISM properties of the ISM of the gravitationally lensed z=2.4 Sunburst Arc. This galaxy is host to a massive, bright, 30 Dor-like young cluster complex which spills copious amounts of LyC emission into the IGM through a line of sight extremely sparse in neutral Hydrogen. Fortunate alignments of the galaxy and the lensing cluster has led to as many as 12 lensed images of this cluster complex, with magnifications allowing us to probe ISM properties on scale locally down to $\lesssim 10$ pc. The combination of the strong magnification and the capabilities of JWST has enabled the mapping of a wealth of ISM properties in the galaxy such as kinematics, ionization structure, and chemical abundance patterns. Together with previous imaging in LyC wavelengths with HST, this dataset makes up the first of its kind, allowing us to map both ionizing production, escape and ISM properties at scales down to individual HII regions. This allows us to spatially correlate physical ISM properties and proposed secondary tracers of LyC escape to high accuracy, allowing unprecedented tests of both escape mechanisms and secondary observational tracers.
