Chris J. Willott, Ross J. McLure, Pascale Hibon, Richard Bielby, Henry J. McCracken, Jean-Paul Kneib, Olivier Ilbert, David G. Bonfield, Victoria A. Bruce, Matt J. Jarvis
We present the results of a search for the most luminous star-forming
galaxies at redshifts z~6 based on CFHT Legacy Survey data. We identify a
sample of 40 Lyman break galaxies brighter than magnitude z'=25.3 across an
area of almost 4 square degrees. Sensitive spectroscopic observations of seven
galaxies provide redshifts for five, of which only two have moderate to strong
Lyman alpha emission lines. All five have clear continuum breaks in their
spectra. Approximately half of the Lyman break galaxies are spatially resolved
in 0.7 arcsec seeing images, indicating larger sizes than lower luminosity
galaxies discovered with the Hubble Space Telescope, possibly due to on-going
mergers. The stacked optical and infrared photometry is consistent with a
galaxy model with stellar mass ~ 10^{10} solar masses. There is strong evidence
for substantial dust reddening with a best-fit A_V=0.75 and A_V>0.48 at 2 sigma
confidence, in contrast to the typical dust-free galaxies of lower luminosity
at this epoch. The spatial extent and spectral energy distribution suggests
that the most luminous z~6 galaxies are undergoing merger-induced starbursts.
The luminosity function of z=5.9 star-forming galaxies is derived. This agrees
well with previous work and shows strong evidence for an exponential decline at
the bright end, indicating that the feedback processes which govern the shape
of the bright end are occurring effectively at this epoch.
View original:
http://arxiv.org/abs/1202.5330
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