1. Spectroscopic Properties of the z=4.5 Lya-Emitters
Steve Dawson (UCB)
in collaboration with
Arjun Dey (NOAO)
Buell Jannuzi (NOAO)
Sangeeta Malhotra (STSci)
James Rhoads (STSci)
Hyron Spinrad (UCB)
Daniel Stern (JPL)
Lya
z=4.5
Intro slide with Lya profiles
Keck/DEIMOS (Dawson et al. 2004b)

2. Follow-up Spectroscopy
Keck/LRIS 400-line grating:
lblaze = 8500
dispersion = / pix
DlFWHM ~ (~ 200 km s-1)
Keck/LRIS 150-line grating:
lblaze = 7500
dispersion = / pix
DlFWHM ~ (~ 1000 km s-1)
Keck/DEIMOS 600-line grating:
dispersion = / pix
DlFWHM ~ (~ 1000 km s-1) i
~ 80 confirming Keck spectra
(selection reliability = 80%) A o
Follow-up Spectroscopy
(Dawson et al. 2004a, 2004b)
Lya
[OII]
Sample individual spectra
Composite Lya line

3. Ensemble Results: EW Distribution
Max. Lya EW predicted
for normal stellar pop.
(Charlot & Fall 1993)
20% - 35% of the Lya-emitters in the spectroscopic sample show EW > 240 A.
Normal star formation is not powering these sources. What is?

4. AGN Among the z = 4.5 Population?
Lack of detectable X-ray emission (LX < 1042 erg s-1) in deep Chandra ACIS imaging implies: no. (Wang et al. 2004)
Lack of high-ionization state emission lines in spectra of restframe UV implies: no.
f(HeII) < 0.13 f(Lya) (2s)
f(CIV) < 0.08 f(Lya) (2s)
No detectable CIV l1549 emission
No detectable HeII l1640 emission