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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