期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 427, 期 4, 页码 3055-3070出版社
WILEY-BLACKWELL
DOI: 10.1111/j.1365-2966.2012.21996.x
关键词
galaxies: evolution; galaxies: formation; galaxies: high-redshift; galaxies: starburst; ultraviolet: galaxies
资金
- Data Archive at the Space Telescope Science Institute [GO-11563, GO/DP-10086, GO-9803, GO-9425]
- NASA [NAS 5-26555]
- RCUK
- Marie Curie Initial Training Network ELIXIR of the European Commission [PITN-GA-2008-214227]
- STFC Standard Grant
- Science and Technology Facilities Council [PP/E003427/1, ST/G001774/1, ST/H002456/1, ST/G004331/1, ST/I003673/1, ST/G002630/1] Funding Source: researchfish
- STFC [ST/G002630/1, ST/I003673/1, PP/E003427/1, ST/G004331/1, ST/G001774/1, ST/H002456/1] Funding Source: UKRI
We present Gemini/Gemini Near Infrared Spectrograph (GNIRS) spectroscopic observations of four z-band (z approximate to 7) dropout galaxies and Very Large Telescope (VLT)/XSHOOTER observations of one z-band dropout and three Y-band (z approximate to 8-9) dropout galaxies in the Hubble Ultra Deep Field, which were selected with Wide Field Camera 3 imaging on the Hubble Space Telescope. We find no evidence of Lyman alpha emission with a typical 5 sigma sensitivity of 5 x 10(-18) erg cm(-2) s(-1), and use the upper limits on Lyman alpha flux and the broad-band magnitudes to constrain the rest-frame equivalent widths for this line emission. Accounting for incomplete spectral coverage, we survey 3.0 z-band dropouts and 2.9 Y-band dropouts to a Lyman alpha rest-frame equivalent width limit > 120 angstrom (for an unresolved emission line); for an equivalent width limit of 50 angstrom the effective numbers of drop-outs surveyed fall to 1.2 z-band drop-outs and 1.5 Y-band drop-outs. A simple model where the fraction of high rest-frame equivalent width emitters follows the trend seen at z = 3-6.5 is inconsistent with our non-detections at z = 7-9 at the approximate to 1 sigma level for spectrally unresolved lines, which may indicate that a significant neutral H I fraction in the intergalactic medium suppresses the Lyman alpha line in z-drop and Y-drop galaxies at z > 7.
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