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Early epoch star formation: nebular spectroscopy Restframe UV-optical emission line spectroscopy reveals properties of the exciting stars as well as the nebular abundances. Pockets of primordial gas may persist to z ~ 3-4 (Jimenez & Haiman 2006) - offering the possibility of observing ‘first light’ physics at accessible epochs. Propose wide wavelength range, moderate R spectroscopy of colourand morphologically-selected (including lensed) sources up to z ~ 10. PI Bob Fosbury Total time 10n (ELT 42m) #CoIs, team ~5. Skills: lens modelling, photoionization modelling, massive star SED modelling, practical nebular spectroscopy Scientific rationale Use restframe UV-optical spectroscopy to investigate the astrophysics of ultralow metallicity star formation (pop III) Wide wavelength coverage emission line spectroscopy gives nebular abundances, ionizing stellar properties (eg. Teff) and virial and wind kinematics Measurements of - or upper limits on - the stellar continuum constrains the IMF Sources expected to cover a range of metallicity from Z ~ 0 to 10-3 Immediate objectives Preparatory work: candidates are found from multicolour imaging (HST and JWST). The emission lines from these objects dominate the UV-optical spectrum and produce colours quite unlike continuum sources. Cluster lenses can be exploited to go to low intrinsic star formation rates - by searching ‘critical lines’ at specific redshifts. Proposed observations: Long-slit (~1 arcsec) spectroscopy with excellent sky subtraction/absorption correction. Marginally resolved sources (on a scale ~ 200 mas). Wavelength coverage: I (or R) through K. Sources rare - so probably no advantage from multiplexing. Need to select and measure sources from z~3 to the reionization epoch: Ly to z ~ 14 and C IV to z ~ 10.5. The pilot programme will study 5 sources to a limit of mAB ~ 30 (10 hr with JWST in one band). The limiting line flux corresponds to a nebula excited by ~105 O-stars at z = 10. The observation of lensed sources will improve this sensitivity. Observations near critical lines in clusters => gains in sensitivity by factors of 10 or so H II region models predict strong diagnostic lines over a wide wavelength range. He II 1640 is critical for stellar Teff QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. HII region model (log Z = -2) 100 Ly Line flux (-16 erg cm-2 s- 10 [O III] C IV H 1 [Ne III] 0.1 Quick Time™ and a TIFF (Uncompressed) dec ompressor are needed to s ee this pic ture. He II 0.01 0.001 0.0001 0 1000 2000 3000 4000 Rest wavelength (Å) 5000 6000 7000 8000 ELT Justification: Need to access faint lines - especially HeII: photonlimited regime. Discovery imaging done from space - including colourselected gravitationally lensed sources. R chosen to allow the determination of gas ~ 20 km/s Legacy Value: HII region atlas Data Reduction: Computation of ‘critical lines’ for selected redshifts in clusters. Extraction of emission line measurements in non-optimum parts of atmospheric windows Target list: 5 sources brighter than mAB = 30. Total on-target time = 100h Run MP Mode AO T. FOV Pixel Notes A 1 R=5000 GLAO 5h/ band 1” 100 I,J,H,K Long slit