Oral Presentation

The Mean Absorption Line Spectra of Luminous z∼6 Lyman Break Galaxies

Author(s): Yuichi Harikane (University of Tokyo & University College London), Nicolas Laporte (University of Cambridge), Richard Ellis (University College London), and Yoshiki Matsuoka (Ehime University)

Presenter: Yuichi Harikane (University of Tokyo & University College London)

We examine the absorption line spectra of a sample of 31 luminous (MUV~-23) Lyman break galaxies at redshift z~6 using data taken with the FOCAS and OSIRIS spectrographs on the Subaru and GTC telescopes. For two of these sources we present longer exposure data taken at higher spectral resolution from ESO’s X-shooter spectrograph. From maximum absorption line depths of SiII1260 and CII1334, we infer a mean covering fraction of >0.85+/-0.16 for our sample. This is larger than that determined using similar methods for lower luminosity galaxies at slightly lower redshifts, suggesting that luminous galaxies do not play a prominent role in concluding reionization. Using various absorption lines we deduce gas-phase and stellar metallicities of ~1 and 0.4 Zsun at z~6, respectively. We discuss the implications of these metallicity estimates for the typical ages of our luminous galaxies and conclude our results imply initial star formation at redshifts z~10, consistent with independent analyses of earlier objects.