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Spectroscopic Properties of z=4.5 Lya-Emitters

Investigating the properties of z=4.5 Lyman-alpha emitters using Keck spectroscopy to uncover their nature and explore possible AGN among the population. Lack of X-ray and high-ionization emission lines suggests a non-stellar source of power.

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Spectroscopic Properties of z=4.5 Lya-Emitters

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  1. Lya z=4.5 Lya z=4.5 Lya z=4.5 Lya z=4.5 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) Keck/DEIMOS (Dawson et al. 2004b)

  2. o o o o o o o o o A A A A A A A A A Follow-up Spectroscopy (Dawson et al. 2004a, 2004b) • Keck/LRIS 400-line grating: • lblaze = 8500 • dispersion = 1.86 / pix • DlFWHM ~ 6 (~ 200 km s-1) • Keck/LRIS 150-line grating: • lblaze = 7500 • dispersion = 4.8 / pix • DlFWHM ~ 25 (~ 1000 km s-1) • Keck/DEIMOS 600-line grating: • lblaze = 7500 • dispersion = 0.65 / pix • DlFWHM ~ 3.5 (~ 1000 km s-1) • i • ~ 80 confirming Keck spectra • (selection reliability = 80%) Sample individual spectra Lya Lya [OII] Lya 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

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