Deep Very Large Telescope/MUSE optical integral field spectroscopy has recently revealed an abundant population of ultra-faint galaxies (
Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher.
Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?
Some links on this page may take you to non-federal websites. Their policies may differ from this site.
-
more » « less
Abstract M UV≈ −15; 0.01L ⋆) atz = 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 , [Oiii ], 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 [Oiii ]/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.
