%0 Generic %1 Ono2011 %A Ono, Yoshiaki %A Ouchi, Masami %A Mobasher, Bahram %A Dickinson, Mark %A Penner, Kyle %A Shimasaku, Kazuhiro %A Weiner, Benjamin J. %A Kartaltepe, Jeyhan S. %A Nakajima, Kimihiko %A Nayyeri, Hooshang %A Stern, Daniel %A Kashikawa, Nobunari %A Spinrad, Hyron %D 2011 %K high-z lya spectra %T Spectroscopic Confirmation of Three z-Dropout Galaxies at z = 6.844 - 7.213: Lyman Alpha Demography of z ~ 7 Galaxies %U http://arxiv.org/abs/1107.3159 %X We present the results of our ultra-deep Keck/DEIMOS spectroscopy of z-dropout galaxies in the SDF and GOODS-N. For 3 out of 11 objects, we detect an emission line at ~ 1um with a signal-to-noise ratio of ~ 10. The lines show asymmetric profiles with high weighted skewness values, consistent with being Lya, yielding redshifts of z=7.213, 6.965, and 6.844. Specifically, we confirm the z=7.213 object in two independent DEIMOS runs with different spectroscopic configurations. The z=6.965 object is a known Lya emitter, IOK-1, for which our improved spectrum at a higher resolution yields a robust skewness measurement. The three z-dropouts have Lya fluxes of 3 x 10^-17 erg s^-1 cm^-2 and rest-frame equivalent widths EW_0^Lya = 33-43A. Based on the largest spectroscopy sample of 43 z-dropouts that is the combination of our and previous data, we find that the fraction of Lya-emitting galaxies (EW_0^Lya > 25A) is low at z ~ 7; 17 +- 10% and 24 +- 12% for bright (Muv ~= -21) and faint (Muv ~= -19.5) galaxies, respectively. The fractions of Lya-emitting galaxies drop from z ~ 6 to 7 and the amplitude of the drop is larger in faint galaxies than in bright galaxies. These two pieces of evidence would indicate that the neutral hydrogen fraction of the IGM increases from z ~ 6 to 7, and that the reionization proceeds from high- to low-density environments, as suggested by an inside-out reionization model.

@misc{Ono2011, abstract = { We present the results of our ultra-deep Keck/DEIMOS spectroscopy of z-dropout galaxies in the SDF and GOODS-N. For 3 out of 11 objects, we detect an emission line at ~ 1um with a signal-to-noise ratio of ~ 10. The lines show asymmetric profiles with high weighted skewness values, consistent with being Lya, yielding redshifts of z=7.213, 6.965, and 6.844. Specifically, we confirm the z=7.213 object in two independent DEIMOS runs with different spectroscopic configurations. The z=6.965 object is a known Lya emitter, IOK-1, for which our improved spectrum at a higher resolution yields a robust skewness measurement. The three z-dropouts have Lya fluxes of 3 x 10^-17 erg s^-1 cm^-2 and rest-frame equivalent widths EW_0^Lya = 33-43A. Based on the largest spectroscopy sample of 43 z-dropouts that is the combination of our and previous data, we find that the fraction of Lya-emitting galaxies (EW_0^Lya > 25A) is low at z ~ 7; 17 +- 10% and 24 +- 12% for bright (Muv ~= -21) and faint (Muv ~= -19.5) galaxies, respectively. The fractions of Lya-emitting galaxies drop from z ~ 6 to 7 and the amplitude of the drop is larger in faint galaxies than in bright galaxies. These two pieces of evidence would indicate that the neutral hydrogen fraction of the IGM increases from z ~ 6 to 7, and that the reionization proceeds from high- to low-density environments, as suggested by an inside-out reionization model. }, added-at = {2011-07-19T23:53:15.000+0200}, author = {Ono, Yoshiaki and Ouchi, Masami and Mobasher, Bahram and Dickinson, Mark and Penner, Kyle and Shimasaku, Kazuhiro and Weiner, Benjamin J. and Kartaltepe, Jeyhan S. and Nakajima, Kimihiko and Nayyeri, Hooshang and Stern, Daniel and Kashikawa, Nobunari and Spinrad, Hyron}, biburl = {https://www.bibsonomy.org/bibtex/26b7cf946dd42dba6d2b754e23096186a/miki}, description = {[1107.3159] Spectroscopic Confirmation of Three z-Dropout Galaxies at z = 6.844 - 7.213: Lyman Alpha Demography of z ~ 7 Galaxies}, interhash = {aa219416d93032371ee47e02ac168029}, intrahash = {6b7cf946dd42dba6d2b754e23096186a}, keywords = {high-z lya spectra}, note = {cite arxiv:1107.3159Comment: 14 pages, 8 figures, submitted to ApJ}, timestamp = {2011-07-19T23:53:15.000+0200}, title = {Spectroscopic Confirmation of Three z-Dropout Galaxies at z = 6.844 - 7.213: Lyman Alpha Demography of z ~ 7 Galaxies}, url = {http://arxiv.org/abs/1107.3159}, year = 2011 }