Between the Extremes: A JWST Spectroscopic Benchmark for High-redshift Galaxies Using ~500 Confirmed Sources at $z\geqslant5$

Understand

The exceptional spectra of the most luminous $z>10$ sources observed so far have challenged our understanding of early galaxy evolution, requiring a new observational benchmark for meaningful interpretation.

• As such, we construct spectroscopic templates representative of high-redshift, star-forming populations, using 482 confirmed sources at $z=5.0-12.9$ with JWST/NIRSpec prism observations, and report on their average properties.
• We find $z=5-11$ galaxies are dominated by blue UV continuum slopes ($\beta=-2.3$ to $-2.7$) and reduced Balmer indices, characteristic of dust-poor and young systems, with a shift towards bluer slopes and younger ages with redshift.
• The evolution is mirrored by ubiquitous CIII] detections across all redshifts (rest-frame equivalent widths of $=5-14$ \r{A}), which increase in strength towards early times.