PI

Total time

#CoIs, team

Bob Fosbury

10n (ELT 42m)

~5. Skills: lens modelling, photoionization modelling, massive star SED modelling, practical nebular spectroscopy

Early epoch star formation: nebular spectroscopyRestframe 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 colour- and morphologically-selected (including lensed) sources up to z ~ 10.

Scientific rationaleUse restframe UV-optical spectroscopy to investigate the astrophysics of ultra-

low 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 objectivesPreparatory 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.

HII region model (log Z = -2)

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Rest wavelength (Å)

Line flux (-16 erg cm

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s- C IV

Ly

[Ne III]

[O III]H

He II

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Observations near critical lines in clusters => gains in sensitivity by factors of 10 or soH II region models predict strong diagnostic lines over a wide wavelength range. He II 1640 is critical for stellar Teff

ELT Justification: Need to access faint lines - especially HeII: photon-limited regime. Discovery imaging done from space - including colour-selected 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