Contatto di riferimento: Alessio Mucciarelli
Partecipanti: Stephane De Barros (INAF-OABo)
Abstract
The cosmic reionization is an important process occurring in the early epochs of the Universe. However, because of observational limitations due to the opacity of the intergalactic medium to Lyman continuum photons, the nature of ionizing sources is still not well constrained. While galaxies (vs. AGN) are thought to be the main contributors to the cosmic reionization, 15 years of search for high-redshift galaxy emitting ionizing photons have been unsuccessful.
I will present the first high-redshift galaxy unambiguously emitting ionizing photons identified at z=3.2, based on UV to NIR spectroscopy and extensive multi-wavelength photometry. This galaxy exhibits a range of physical properties (e.g., Lyman-alpha emission, covering fraction, abundances) consistent with theoretical expectations for a Lyman continuum emitter. We also detect a signal in the UV spectrum consistent with direct Lyman continuum detection (S/N>5).
Finally, recent HST observations provided the final evidence that this galaxy is indeed a Lyman continuum emitter.
The properties of this galaxy can be used as a guideline to detect Lyman continuum emitters at fainter luminosity regime where most of the reionization contributors are thought to be. Interestingly, our candidate also has properties similar to z~7 galaxies, in the reionization epoch.