Lyman continuum leakage in z 0.3 - 0.4 dwarf compact star-forming galaxies with stellar masses < 1.e8 Msun
One of the key questions in observational cosmology is the identification of the sources responsible for cosmic reionization. The general consensus is that a population of faint low-mass galaxies must be responsible for the bulk of the ionizing photons. However, until recently, attempts at identifying individual galaxies showing Lyman continuum (LyC) leakage have only found very few such galaxies, both at high and low redshifts. A breakthrough was recently achieved by Izotov et al. (2016ab, 2018ab), who detected LyC emission in eleven out of eleven low-redshift (z 0.3) compact star-forming galaxies (SFG) with LyC escape fractions of 2-72%, using HST/COS observations. However, all these galaxies have relatively high stellar masses > 1e8 solar masses while it is generally thought that the lower mass galaxies were the main sources of the reionization of the Universe. It is proposed here to extend previous studies to nine compact SFGs at z 0.3-0.4 with lower stellar masses in the range 2e7 - 1e8 Msun, a range which has not been explored by HST/COS. This will allow to determine if they are also LyC leakers and if the LyC escape fraction continues to rise with decreasing stellar masses. Finally the requested COS observations will allow for the determination of the Lyman alpha line profile of these objects, providing thus an empirical probe of this indirect LyC leakage indicator. Since the low-mass compact SFGs share many properties with typical SFGs at high redshift this study will provide important insight on the sources of cosmic reionization.
- Pub Date:
- November 2018