%0 Generic %1 zitrin2015lymanalpha %A Zitrin, Adi %A Labbe, Ivo %A Belli, Sirio %A Bouwens, Rychard %A Ellis, Richard S. %A Roberts-Borsani, Guido %A Stark, Daniel P. %A Oesch, Pascal A. %A Smit, Renske %D 2015 %K alpha emission high-z lyman %T Lyman-alpha Emission from a Luminous z=8.68 Galaxy: Implications for Galaxies as Tracers of Cosmic Reionization %U http://arxiv.org/abs/1507.02679 %X We report the discovery of Lyman-alpha emission (Ly$\alpha$) in the bright galaxy EGSY-2008532660 (hereafter EGSY8p7) using the MOSFIRE spectrograph at the Keck Observatory. First reported by Roberts-Borsani et al. (2015), it was selected for spectroscopic observations because of its photometric redshift ($z_phot=8.57^+0.22_-0.43$), apparent brightness (H$_160=25.26\pm0.09$) and red Spitzer/IRAC 3.6-4.5 color indicative of contamination by strong oxygen emission in the 4.5 band. With a total integration of $\sim4.3$ hours, our data reveal an emission line at $\simeq11776$ \AA which we argue is likely Ly$\alpha$ at a redshift $z_spec=8.68$, in good agreement with the photometric estimate. The line was detected independently on two nights using different slit orientations and its detection significance is $\sim7.5\sigma$. An overlapping sky line contributes significantly to the uncertainty on the total line flux but not the overall significance. By direct addition and a Gaussian fit, we estimate a 95\% confidence range of 1.0 - 2.5 $\times 10^-17$ ergs cm$^-2$ sec$^-1$, corresponding to a rest-frame equivalent width of 17 - 42 \AA\ . EGSY8p7 is the most distant galaxy confirmed spectroscopically to date, and the third luminous source in the EGS field beyond $z_phot\gtrsim7.5$ with detectable Ly$\alpha$ emission viewed at a time when the intergalactic medium is expected to be fairly neutral. Although the reionization process was probably patchy, we discuss whether luminous sources with prominent IRAC color excesses may harbor harder ionizing spectra than the dominant fainter population thereby creating earlier ionized bubbles. Further spectroscopic follow-up of such bright sources promises important insight into the early formation of galaxies.

@misc{zitrin2015lymanalpha, abstract = {We report the discovery of Lyman-alpha emission (Ly$\alpha$) in the bright galaxy EGSY-2008532660 (hereafter EGSY8p7) using the MOSFIRE spectrograph at the Keck Observatory. First reported by Roberts-Borsani et al. (2015), it was selected for spectroscopic observations because of its photometric redshift ($z_{phot}=8.57^{+0.22}_{-0.43}$), apparent brightness (H$_{160}=25.26\pm0.09$) and red Spitzer/IRAC [3.6]-[4.5] color indicative of contamination by strong oxygen emission in the [4.5] band. With a total integration of $\sim4.3$ hours, our data reveal an emission line at $\simeq11776$ {\AA} which we argue is likely Ly$\alpha$ at a redshift $z_{spec}=8.68$, in good agreement with the photometric estimate. The line was detected independently on two nights using different slit orientations and its detection significance is $\sim7.5\sigma$. An overlapping sky line contributes significantly to the uncertainty on the total line flux but not the overall significance. By direct addition and a Gaussian fit, we estimate a 95\% confidence range of 1.0 - 2.5 $\times 10^{-17}$ ergs cm$^{-2}$ sec$^{-1}$, corresponding to a rest-frame equivalent width of 17 - 42 \AA\ . EGSY8p7 is the most distant galaxy confirmed spectroscopically to date, and the third luminous source in the EGS field beyond $z_{phot}\gtrsim7.5$ with detectable Ly$\alpha$ emission viewed at a time when the intergalactic medium is expected to be fairly neutral. Although the reionization process was probably patchy, we discuss whether luminous sources with prominent IRAC color excesses may harbor harder ionizing spectra than the dominant fainter population thereby creating earlier ionized bubbles. Further spectroscopic follow-up of such bright sources promises important insight into the early formation of galaxies.}, added-at = {2015-07-13T10:05:57.000+0200}, author = {Zitrin, Adi and Labbe, Ivo and Belli, Sirio and Bouwens, Rychard and Ellis, Richard S. and Roberts-Borsani, Guido and Stark, Daniel P. and Oesch, Pascal A. and Smit, Renske}, biburl = {https://www.bibsonomy.org/bibtex/2c027916b26597af65603230ab2328f30/miki}, description = {[1507.02679] Lyman-alpha Emission from a Luminous z=8.68 Galaxy: Implications for Galaxies as Tracers of Cosmic Reionization}, interhash = {04578cc15d3bf8875b6a21ad69a953c1}, intrahash = {c027916b26597af65603230ab2328f30}, keywords = {alpha emission high-z lyman}, note = {cite arxiv:1507.02679Comment: ApJL Submitted; 6 pages, 4 figures, 1 table}, timestamp = {2015-07-13T10:05:57.000+0200}, title = {Lyman-alpha Emission from a Luminous z=8.68 Galaxy: Implications for Galaxies as Tracers of Cosmic Reionization}, url = {http://arxiv.org/abs/1507.02679}, year = 2015 }