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No evidence for Lyman emission in spectroscopy of z > 7 candidate galaxies

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posted on 2023-06-08, 14:47 authored by Joseph Caruana, Andrew J Bunker, Stephen WilkinsStephen Wilkins, Elizabeth Stanway, Mark Lacy, Matt J Jarvis, Silvio Lorenzoni, Samantha Hickey
We present Gemini/Gemini Near Infrared Spectrograph (GNIRS) spectroscopic observations of four z-band (z ˜ 7) dropout galaxies and Very Large Telescope (VLT)/XSHOOTER observations of one z-band dropout and three Y-band (z ˜ 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 a emission with a typical 5s sensitivity of 5 × 10-18?erg cm-2?s-1, and use the upper limits on Lyman a 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 a rest-frame equivalent width limit >120 Å (for an unresolved emission line); for an equivalent width limit of 50 Å 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 ˜1s level for spectrally unresolved lines, which may indicate that a significant neutral H?I fraction in the intergalactic medium suppresses the Lyman a line in z-drop and Y-drop galaxies at z > 7.

History

Publication status

  • Published

File Version

  • Published version

Journal

Monthly Notices of the Royal Astronomical Society

ISSN

0035-8711

Publisher

Wiley-Blackwell

Issue

4

Volume

427

Page range

3055-3070

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2013-04-26

First Open Access (FOA) Date

2016-03-22

First Compliant Deposit (FCD) Date

2016-08-17

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