%0 Generic %1 matthee2015identification %A Matthee, Jorryt %A Sobral, David %A Santos, Sérgio %A Röttgering, Huub %A Darvish, Behnam %A Mobasher, Bahram %D 2015 %K emission function luminosity lya %T Identification of the brightest Ly\alpha\ emitters at z=6.6: implications for the evolution of the luminosity function in the re-ionisation era %U http://arxiv.org/abs/1502.07355 %X Using wide field narrow-band surveys, we provide a new measurement of the $z=6.6$ Lyman-$\alpha$ Emitter (LAE) luminosity function (LF), which constraints the bright end for the first time. We use a combination of archival narrow-band NB921 data in UDS and new NB921 measurements in SA22 and COSMOS/UltraVISTA, all observed with the Subaru telescope, with a total area of $5$ deg$^2$. We exclude lower redshift interlopers by using broad-band optical and near-infrared photometry and also exclude three supernovae with data split over multiple epochs. We spectroscopically confirm the two most luminous Ly$\alpha$ emitters ever found at $z=6.604$ and $6.541$ in the COSMOS field using Keck/DEIMOS and VLT/FORS2. Combining the UDS and COSMOS samples we find no evolution of the bright end of the Ly$\alpha$ LF between $z=5.7$ and $6.6$, which is supported by spectroscopic follow-up, and conclude that Himiko-like sources are not as rare as previously thought, with number densities of $1.5\times10^-5$ Mpc$^-3$. Combined with our wide-field SA22 measurements, our results indicate a non-Schechter-like bright end of the LF at $z=6.6$ and a different evolution of observed faint and bright LAEs. This differential evolution was not addressed in previous studies, or discarded as cosmic variance, but we argue instead that it may be an effect of re-ionisation. Using a toy-model, we show that such differential evolution of the LF is expected, since brighter sources are able to ionise their surroundings earlier, such that Ly$\alpha$ photons are able to escape. Our targets are excellent candidates for detailed follow-up studies and provide the possibility to give a unique view on the earliest stages in the formation of galaxies and re-ionisation process.

@misc{matthee2015identification, abstract = {Using wide field narrow-band surveys, we provide a new measurement of the $z=6.6$ Lyman-$\alpha$ Emitter (LAE) luminosity function (LF), which constraints the bright end for the first time. We use a combination of archival narrow-band NB921 data in UDS and new NB921 measurements in SA22 and COSMOS/UltraVISTA, all observed with the Subaru telescope, with a total area of $\sim 5$ deg$^2$. We exclude lower redshift interlopers by using broad-band optical and near-infrared photometry and also exclude three supernovae with data split over multiple epochs. We spectroscopically confirm the two most luminous Ly$\alpha$ emitters ever found at $z=6.604$ and $6.541$ in the COSMOS field using Keck/DEIMOS and VLT/FORS2. Combining the UDS and COSMOS samples we find no evolution of the bright end of the Ly$\alpha$ LF between $z=5.7$ and $6.6$, which is supported by spectroscopic follow-up, and conclude that \emph{Himiko}-like sources are not as rare as previously thought, with number densities of $\sim 1.5\times10^{-5}$ Mpc$^{-3}$. Combined with our wide-field SA22 measurements, our results indicate a non-Schechter-like bright end of the LF at $z=6.6$ and a different evolution of \emph{observed} faint and bright LAEs. This differential evolution was not addressed in previous studies, or discarded as cosmic variance, but we argue instead that it may be an effect of re-ionisation. Using a toy-model, we show that such differential evolution of the LF is expected, since brighter sources are able to ionise their surroundings earlier, such that Ly$\alpha$ photons are able to escape. Our targets are excellent candidates for detailed follow-up studies and provide the possibility to give a unique view on the earliest stages in the formation of galaxies and re-ionisation process.}, added-at = {2015-02-27T12:09:28.000+0100}, author = {Matthee, Jorryt and Sobral, David and Santos, Sérgio and Röttgering, Huub and Darvish, Behnam and Mobasher, Bahram}, biburl = {https://www.bibsonomy.org/bibtex/2e3807cd03a37d7f2b90d8ebbff12dcbb/miki}, description = {[1502.07355] Identification of the brightest Ly\alpha\ emitters at z=6.6: implications for the evolution of the luminosity function in the re-ionisation era}, interhash = {99081130643fe677121688be773f130f}, intrahash = {e3807cd03a37d7f2b90d8ebbff12dcbb}, keywords = {emission function luminosity lya}, note = {cite arxiv:1502.07355Comment: 20 pages, main results shown in Fig. 6 and Fig. 7, submitted to MNRAS}, timestamp = {2015-02-27T12:09:28.000+0100}, title = {Identification of the brightest Ly\alpha\ emitters at z=6.6: implications for the evolution of the luminosity function in the re-ionisation era}, url = {http://arxiv.org/abs/1502.07355}, year = 2015 }