JWST /NIRSpec spectroscopy of z = 7–9 star-forming galaxies with CEERS: new insight into bright Lyα emitters in ionized bubbles - Archive ouverte HAL Access content directly
Journal Articles Monthly Notices of the Royal Astronomical Society Year : 2023

JWST /NIRSpec spectroscopy of z = 7–9 star-forming galaxies with CEERS: new insight into bright Lyα emitters in ionized bubbles

Mengtao Tang
  • Function : Author
Daniel P Stark
  • Function : Author
Zuyi Chen
  • Function : Author
Charlotte Mason
  • Function : Author
Michael Topping
  • Function : Author
Ryan Endsley
  • Function : Author
Peter Senchyna
  • Function : Author
Adèle Plat
  • Function : Author
Ting-Yi Lu
  • Function : Author
Lily Whitler
  • Function : Author
Brant Robertson
  • Function : Author

Abstract

ABSTRACT We describe new JWST/NIRSpec observations of galaxies at z ≳ 7 taken from the CEERS survey. Previous observations of this area have revealed associations of Lyα emitters at redshifts (z = 7.5, 7.7, and 8.7) where the intergalactic medium (IGM) is thought to be mostly neutral, leading to suggestions that these systems are situated in large ionized bubbles. We identify 21 z ≳ 7 galaxies with robust redshifts in the CEERS data set, including 10 in the Lyα associations. Their spectra are indicative of very highly ionized and metal poor gas, with line ratios (O32 = 17.84 and Ne3O2 = 0.89, linear scale) and metallicity ($12+\log {(\rm {O/H})}=7.84$) that are rarely seen at lower redshifts. We find that the most extreme spectral properties are found in the six z ≳ 7 Lyα emitters in the sample. Each has a hard ionizing spectrum indicating that their visibility is likely enhanced by efficient ionizing photon production. Lyα velocity offsets are found to be very large (≳300 km s−1), likely also contributing to their detectability. We find that Lyα in z ≳ 7 galaxies is 6–12 × weaker than in lower redshift samples with matched rest-optical spectral properties. If the bubbles around the Lyα emitters are relatively small (≲0.5–1 pMpc), we may expect such significant attenuation of Lyα in these ionized regions. We discuss several other effects that may contribute to weaker Lyα emission at z ≳ 7. Deep spectroscopy of fainter galaxies in the vicinity of the Lyα emitters will better characterize the physical scale of the ionized bubbles in this field.
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Dates and versions

hal-04293545 , version 1 (18-11-2023)

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Mengtao Tang, Daniel P Stark, Zuyi Chen, Charlotte Mason, Michael Topping, et al.. JWST /NIRSpec spectroscopy of z = 7–9 star-forming galaxies with CEERS: new insight into bright Lyα emitters in ionized bubbles. Monthly Notices of the Royal Astronomical Society, 2023, 526 (2), pp.1657-1686. ⟨10.1093/mnras/stad2763⟩. ⟨hal-04293545⟩
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