An atlas of z = 5.7 and z = 6.5 Lyα emitters

Abstract

We present an atlas of 88 z ~ 5.7 and 30 z ~ 6.5 Lyα emitters obtained from a wide-field narrowband survey. We combined deep narrowband imaging in 120 Å bandpass filters centered at 8150 Å and 9140 Å with deep B V R I z broadband imaging to select high-redshift galaxy candidates over an area of 4180 arcmin^2. The goal was to obtain a uniform selection of comparable depth over the seven targeted fields in the two filters. For the GOODS-North region of the Hubble Deep Field-North field, we also selected candidates using a 120 Å filter centered at 9210 Å. We made spectroscopic observations with Keck DEIMOS of nearly all the candidates to obtain the final sample of Lyα emitters. At the 3.3 Å resolution of the DEIMOS observations the asymmetric profile for Lyα emission can be clearly seen in the spectra of nearly all the galaxies. We show that the spectral profiles are surprisingly similar for many of the galaxies and that the composite spectral profiles are nearly identical at z = 5.7 and z = 6.5.We analyze the distributions of line widths and Lyα equivalent widths and find that the lines are marginally narrower at the higher redshift, with median values of 0.77 Å at z = 6.5 and 0.92 Å at z = 5.7. The line widths have a dependence on the Lyα luminosity of the form ~L^(0.3)_α . We compare the surface densities and the luminosity functions at the two redshifts and find that there is a multiplicative factor of two decrease in the number density of bright Lyα emitters from z = 5.7 to z = 6.5, while the characteristic luminosity is unchanged.

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