Abstract

With the recent discovery of quiescent galaxies at z>3, studying of dusty star-forming galaxies at high redshift became more vital than ever, as they are thought to be precursors of quiescent galaxies. However, until the launch of JWST , studying the rest-frame of optical emission of these sources at redshifts higher than 3 was out of reach of astronomers, often solely relying on the ALMA observations of their FIR emission lines. In this talk, I will present one of the first JWST /NIRSpec IFS data of a massive dusty star-forming galaxy at the Epoch of Reionisation. COS -3018, is a unique UV bright galaxy (LUV>2 L*) at z~6.8, previously only observed using ALMA ([CII]158 microns, [OIII] 88 microns), VLT X -Shooter (Lyman-alpha) and HST broadband photometry. Furthermore, this galaxy has a large amount of dust (log Mdust =10.7 Msol) and an excess of [OIII]88micron emission suggesting that this might be an AGN or has non-standard ISM conditions such as AGN . I will present deep high-resolution JWST /NIRSpec IFS observations of rest-frame UV and optical continuum and emission lines, in combination with deep ALMA [CII] and [OIII]88micron observations and NIR Cam photometry. Using the deep and unique NIR Spec IFS (PRISM+R2700) observations, I will show the ISM conditions in this unique galaxy: excitation conditions (extreme star formation or AGN ?), metallicity gradient, location of dust obscured (from ALMA high resolution observations) and unobscured star formation. Finally, I will answer the question: What is driving such an extreme production of dust in this galaxy and UV luminosity in this galaxy?