Roberts-Borsani, Guido;
Treu, Tommaso;
Shapley, Alice;
Fontana, Adriano;
Pentericci, Laura;
Castellano, Marco;
Morishita, Takahiro;
... Rosati, Piero; + view all
(2024)
Between the Extremes: A JWST Spectroscopic Benchmark for High-redshift Galaxies Using ∼500 Confirmed Sources at z ≥ 5.
The Astrophysical Journal
, 976
(2)
, Article 193. 10.3847/1538-4357/ad85d3.
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Abstract
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 (β = −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 C iii] detections across all redshifts (rest-frame equivalent widths of 5−14 Å), which increase in strength towards early times. Rest-frame optical lines reveal elevated ratios (O32 = 7-31, R23 = 5-8, and Ne3O2 = 1−2) and subsolar metallicities (log(O/H) = 7.3−7.9), typical of ionization conditions and metallicities rarely observed in z ∼ 0 populations. Within our sample, we identify 57 Lyα emitters, which we stack and compare to a matched sample of nonemitters. The former are characterized by more extreme ionizing conditions with enhanced C iii], C iv, and He ii + [O iii] line emission, younger stellar populations from Balmer jumps, and a more pristine interstellar medium seen through bluer UV slopes and elevated rest-frame optical line ratios. The novel comparison illustrates important intrinsic differences between the two populations, with implications for Lyα visibility. The spectral templates derived here represent a new observational benchmark with which to interpret high-redshift sources, lifting our constraints on their global properties to unprecedented heights and extending out to the earliest of cosmic times.
| Type: | Article |
|---|---|
| Title: | Between the Extremes: A JWST Spectroscopic Benchmark for High-redshift Galaxies Using ∼500 Confirmed Sources at z ≥ 5 |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4357/ad85d3 |
| Publisher version: | https://doi.org/10.3847/1538-4357/ad85d3 |
| Language: | English |
| Additional information: | Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. |
| Keywords: | Science & Technology, Physical Sciences, Astronomy & Astrophysics, STAR-FORMING GALAXIES, EQUIVALENT-WIDTH DISTRIBUTION, PHOTON PRODUCTION EFFICIENCY, UV LUMINOSITY FUNCTIONS, DUST ATTENUATION CURVE, EXTREMELY METAL-POOR, ALPHA OPTICAL DEPTH, HE II EMISSION, LY-ALPHA, LYMAN-ALPHA |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10220223 |
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