Between the Extremes: A JWST Spectroscopic Benchmark for High-redshift Galaxies Using ~500 Confirmed Sources at $z\geqslant5$
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| Autores principales: | , , , , , , , , |
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| Formato: | Preprint |
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2024
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| author | Roberts-Borsani, Guido Treu, Tommaso Shapley, Alice Fontana, Adriano Pentericci, Laura Castellano, Marco Morishita, Takahiro Bergamini, Pietro Rosati, Piero |
| author_facet | Roberts-Borsani, Guido Treu, Tommaso Shapley, Alice Fontana, Adriano Pentericci, Laura Castellano, Marco Morishita, Takahiro Bergamini, Pietro Rosati, Piero |
| contents | 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 CIII] 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 $z\sim0$ populations. Within our sample, we identify 57 Ly$α$ emitters, which we stack and compare to a matched sample of nonemitters. The former are characterized by more extreme ionizing conditions with enhanced CIII], CIV, and HeII+[OIII] 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 Ly$α$ 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_07103 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Between the Extremes: A JWST Spectroscopic Benchmark for High-redshift Galaxies Using ~500 Confirmed Sources at $z\geqslant5$ Roberts-Borsani, Guido Treu, Tommaso Shapley, Alice Fontana, Adriano Pentericci, Laura Castellano, Marco Morishita, Takahiro Bergamini, Pietro Rosati, Piero Astrophysics of Galaxies 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 CIII] 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 $z\sim0$ populations. Within our sample, we identify 57 Ly$α$ emitters, which we stack and compare to a matched sample of nonemitters. The former are characterized by more extreme ionizing conditions with enhanced CIII], CIV, and HeII+[OIII] 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 Ly$α$ 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. |
| title | Between the Extremes: A JWST Spectroscopic Benchmark for High-redshift Galaxies Using ~500 Confirmed Sources at $z\geqslant5$ |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2403.07103 |