2 research outputs found
JWST/NIRSpec Measurements of Extremely Low Metallicities in High Equivalent Width Lyman- Emitters
Deep VLT/MUSE optical integral field spectroscopy has recently revealed an
abundant population of ultra-faint galaxies (15; 0.01 )
at 2.96.7 due to their strong Lyman- emission. The implied
Lyman- equivalent widths are in excess of 100-200 Angstrom, challenging
existing models of normal star formation and implying extremely young ages,
small stellar masses, and a very low amount of metal enrichment. We use
JWST/NIRSpec's microshutter array to follow-up 45 of these galaxies (11h in
G235M/F170LP and 7h in G395M/F290LP), as well as 45 lower-equivalent width
Lyman- emitters. Our spectroscopy covers the range 1.75.1 micron in
order to target strong optical emission lines: H, [OIII], H, and
[NII]. Individual measurements as well as stacks reveal line ratios consistent
with a metal poor nature (230% ) and intense ionizing radiation
fields. The galaxies with the highest equivalent widths of Lyman-, in
excess of 120 Angstrom, have lower gas-phase metallicities than those with
lower equivalent widths. This implies a selection based on Lyman-
equivalent width is an efficient technique for identifying younger, less
chemically enriched systems.Comment: 13 pages, 4 appendices; submitted to AAS Journal
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JWST/NIRSpec Measurements of Extremely Low Metallicities in High Equivalent Width Lyα Emitters
Abstract
Deep Very Large Telescope/MUSE optical integral field spectroscopy has recently revealed an abundant population of ultra-faint galaxies (M
UV ≈ −15; 0.01 L
⋆) at z = 2.9−6.7 due to their strong Lyα emission with no detectable continuum. The implied Lyα equivalent widths can be in excess of 100–200 Å, challenging existing models of normal star formation and indicating extremely young ages, small stellar masses, and a very low amount of metal enrichment. We use JWST/NIRSpec’s microshutter array to follow up 45 of these galaxies (11 hr in G235M/F170LP and 7 hr in G395M/F290LP), as well as 45 lower-equivalent width Lyα emitters. Our spectroscopy covers the range 1.7−5.1 micron in order to target strong optical emission lines: Hα, [O iii], Hβ, and [N II]. Individual measurements as well as stacks reveal line ratios consistent with a metal-poor nature (2%−40% Z
⊙, depending on the calibration). The galaxies with the highest equivalent widths of Lyα, in excess of 90 Å, have lower [N II]/Hα (1.9σ) and [O iii]/Hβ (2.2σ) ratios than those with lower equivalent widths, implying lower gas-phase metallicities at a combined significance of 2.4σ. This implies a selection based on Lyα equivalent width is an efficient technique for identifying younger, less chemically enriched systems.</jats:p