Stars and gas in the most metal-poor galaxies I: SBS 0335-052E

<p>Understanding the properties of stars and gas at low metallicity is of large relevance for a variety of fields in astrophysics, since it relates to multiple topical questions which range from understanding the properties of galaxies that contributed to cosmic reionization to the evolution of metal-poor massive stars that give rise to the formation of heavy binary black holes. Crucial are observational constraints for the theoretical predictions. These can be obtained from rest-frame ultraviolet and optical spectra of the most metal-poor galaxies known. Among these, SBS 0335-052E (z=0.0135, 12+log(O/H)=7.3) is one of the most well- studied. For this galaxy, we present Hubble Space Telescope (HST) / Cosmic Origins Spectrograph (COS) detections of the C IV 1549, 1551, He II 1640, O III 1661, 1666, [C III] 1907, and C III] 1909 UV emission lines; and a Very Large Telescope (VLT) / Multi Unit Spectroscopic Explorer (MUSE) spectrum covering from 4600 to 9400 Ang, which is co-spatial with the UV data and integrated over the same area. Using these datasets we test: a) the latest Charlot & Bruzal spectral synthesis models with very massive (300 Msun) single non-rotating stars; b) the performance of the spectral analysis tool, BayEsian Analysis of GaLaxy sEds (BEAGLE); and c) the extent to which physical properties of the gas and dust derived independently from the UV and optical with BEAGLE are constrained.</p