CANUCS/Technicolor: JWST Medium-band Photometry Finds Half of the Star Formation at <i>z</i> > 7.5 Is Obscured
Abstract We present a sample of 110 high-redshift ( z > 7.5) galaxies from the CANUCS and Technicolor surveys, showcasing photometry in every wide- and medium-band NIRCam filter in addition to ancillary Hubble Space Telescope data sampling 0.4–5 μ m (22 JWST bands out of 29 bands total). Additionally, 47 (43%) galaxies in our sample meet criteria to be classified as extreme emission line galaxies, 17 (15%) of which are completely missed by typical dropout selections due to faint ultraviolet (UV) emission. By fitting the spectral energy distributions covering the rest-frame UV to optical at z > 7.5, we investigate the dust obscuration properties, giving an unbiased view of dust buildup in high-redshift galaxies free from spectroscopic follow-up selection effects. Dust attenuation correlates with stellar mass, but more strongly with star formation rate. We find typical galaxies at z > 7.5 have ∼25% of their star formation obscured. However, since galaxies with higher star formation rates suffer more attenuation, ∼50% of the total star formation rate density at 7.5 < z < 9 is obscured. The obscured fraction drops to ∼25% in our 9 < z < 12 bin, possibly due to substantial dust grain growth in the interstellar medium not having time to occur. Extrapolating the decline in dust obscuration of galaxies to higher redshifts, we infer that dust obscuration should approach zero at z > 15, implying that epoch as when dust first forms in bright galaxies.
Authors
- Gaël Noirot
- Anishya Harshan (ORCID: https://orcid.org/0000-0001-9414-6382)
- Maruša Bradač (ORCID: https://orcid.org/0000-0001-5984-0395)
- Vladan Markov (ORCID: https://orcid.org/0000-0002-5694-6124)
- Danilo Marchesini (ORCID: https://orcid.org/0000-0001-9002-3502)
- G. Desprez (ORCID: https://orcid.org/0000-0001-8325-1742)
- Roberto Abraham (ORCID: https://orcid.org/0000-0002-4542-921X)
- Adam Muzzin (ORCID: https://orcid.org/0000-0002-9330-9108)
- Chris J. Willott (ORCID: https://orcid.org/0000-0002-4201-7367)
- Ghassan T. E. Sarrouh (ORCID: https://orcid.org/0000-0001-8830-2166)
- Yoshihisa Asada (ORCID: https://orcid.org/0000-0003-3983-5438)
- Rosa M. Mérida (ORCID: https://orcid.org/0000-0001-8115-5845)
- Kartheik G. Iyer (ORCID: https://orcid.org/0000-0001-9298-3523)
- Roberta Tripodi (ORCID: https://orcid.org/0000-0002-9909-3491)
- Marcin Sawicki (ORCID: https://orcid.org/0000-0002-7712-7857)
- Nicholas S. Martis (ORCID: https://orcid.org/0000-0003-3243-9969)
- Victoria Strait (ORCID: https://orcid.org/0000-0002-6338-7295)
- Gabriel Brammer (ORCID: https://orcid.org/0000-0003-2680-005X)
- Sunna Withers (ORCID: https://orcid.org/0009-0000-8716-7695)
- Gregor Rihtaršič (ORCID: https://orcid.org/0009-0009-4388-898X)
- Jon Judež (ORCID: https://orcid.org/0009-0000-2101-1938)
- Giordano Felicioni (ORCID: https://orcid.org/0009-0001-0778-9038)
- Naadiyah Jagga (ORCID: https://orcid.org/0009-0009-9848-3074)
Publication Details
- Journal
- The Astrophysical Journal
- Published
- 2025-08-29
- DOI
- https://doi.org/10.3847/1538-4357/adf32a
- Citations
- 2
- Primary Topic
- Galaxies: Formation, Evolution, Phenomena
- Type
- article
- Field-Weighted Citation Impact
- 2.31
Funders
- National Aeronautics and Space Administration
- Canadian Foundation for AIDS Research
- Canarie
- Space Telescope Science Institute
- National Research Foundation
- Danmarks Grundforskningsfond
- Javna Agencija za Raziskovalno Dejavnost RS
- Alliance de recherche numérique du Canada
- Canadian Space Agency
- Natural Sciences and Engineering Research Council of Canada