TY - JOUR
T1 - NEW OBSERVATIONS OF z ~ 7 GALAXIES
T2 - EVIDENCE FOR A PATCHY REIONIZATION
AU - Pentericci, L.
AU - Vanzella, E.
AU - Fontana, A.
AU - Castellano, M.
AU - Treu, T.
AU - Mesinger, A.
AU - Dijkstra, M.
AU - Grazian, A.
AU - Bradac, M.
AU - Conselice, C.
AU - Cristiani, S.
AU - Dunlop, J.
AU - Galametz, A.
AU - Giavalisco, M.
AU - Giallongo, E.
AU - Koekemoer, A.
AU - McLure, R.
AU - Maiolino, R.
AU - Paris, D.
AU - Santini, P.
PY - 2014/10/1
Y1 - 2014/10/1
N2 - We present new results from our search for z similar to 7 galaxies from deep spectroscopic observations of candidate z dropouts in the CANDELS fields. Despite the extremely low flux limits achieved by our sensitive observations, only two galaxies have robust redshift identifications, one from its Ly alpha emission line at z = 6.65, the other from its Lyman break, i.e., the continuum discontinuity at the Ly alpha wavelength consistent with a redshift of 6.42 but with no emission line. In addition, for 23 galaxies we present deep limits in the Ly alpha equivalent width derived from the nondetections in ultradeep observations. Using this new data as well as previous samples, we assemble a total of 68 candidate z similar to 7 galaxies with deep spectroscopic observations, of which 12 have a line detection. With this much enlarged sample we can place solid constraints on the declining fraction of Ly alpha emission in z similar to 7 Lyman-break galaxies compared to z similar to 6, both for bright and faint galaxies. Applying a simple analytical model, we show that the present data favor a patchy reionization process rather than a smooth one.
AB - We present new results from our search for z similar to 7 galaxies from deep spectroscopic observations of candidate z dropouts in the CANDELS fields. Despite the extremely low flux limits achieved by our sensitive observations, only two galaxies have robust redshift identifications, one from its Ly alpha emission line at z = 6.65, the other from its Lyman break, i.e., the continuum discontinuity at the Ly alpha wavelength consistent with a redshift of 6.42 but with no emission line. In addition, for 23 galaxies we present deep limits in the Ly alpha equivalent width derived from the nondetections in ultradeep observations. Using this new data as well as previous samples, we assemble a total of 68 candidate z similar to 7 galaxies with deep spectroscopic observations, of which 12 have a line detection. With this much enlarged sample we can place solid constraints on the declining fraction of Ly alpha emission in z similar to 7 Lyman-break galaxies compared to z similar to 6, both for bright and faint galaxies. Applying a simple analytical model, we show that the present data favor a patchy reionization process rather than a smooth one.
KW - galaxies: distances and redshifts
KW - galaxies: formation
KW - galaxies: high-redshift
KW - LYMAN-BREAK GALAXIES
KW - LY-ALPHA-EMITTERS
KW - STAR-FORMING GALAXIES
KW - COSMIC REIONIZATION
KW - SPECTROSCOPIC CONFIRMATION
KW - LUMINOSITY FUNCTION
KW - KECK SPECTROSCOPY
KW - PROBING REIONIZATION
KW - IONIZING EMISSIVITY
KW - EARLIEST GALAXIES
U2 - 10.1088/0004-637X/793/2/113
DO - 10.1088/0004-637X/793/2/113
M3 - Article
VL - 793
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
M1 - 113
ER -