MIRI spectrophotometry of GN-z11: Detection and nature of an optical red continuum component
Year: 2026
Type: article
Abstract: We present new MIRI F560W, F770W, and F1000W imaging of the galaxy GN-z11 at a redshift of 10.603. We report a significant detection (14 σ ) in the F560W and F770W images, and a marginal detection (3.2 σ ) in the F1000W filter. The new MIRI observations cover the optical-red spectral range and significantly extend previous NIRCam wavelength coverage from rest-frame 0.38 μm up to 0.86 μm. In this work, we analyse the spectral energy distribution (SED) combining this new MIRI imaging data with archival NIRSpec/Prism and MRS spectroscopy, and NIRCam imaging, i.e. covering the rest-frame 0.12–0.86 μm. New constraints such as the equivalent widths of the strong optical lines ([O III ] λ 5008, H β and H α ) and the continuum emission at rest-frame 0.48 μm, 0.66 μm, and 0.86 μm, free of emission line contributions, are presented. The continuum emission shows a flat energy distribution, in f ν , up to 0.5 μm, compatible with the presence of a mixed stellar population of young (4 ± 1 Myr) and mature (63 ± 23 Myr) stars that also account for the [O III ], H β , and H α emission lines. The continuum at rest-frame 0.66 μm shows a 36 ± 3% flux excess above the predicted flux for a mixed stellar population, pointing to the presence of an additional source contributing at these wavelengths. This excess increases to 91 ± 28% at rest-frame 0.86 μm, although with a large uncertainty due to the marginal detection in the F1000W filter. We consider that hot dust emission in the dusty torus around a type 2 active galactic nucleus (AGN) could be responsible for the observed excess. Alternatively, this excess could be due to hot dust emission or a photoluminiscence dust process (Extended Red Emission, ERE) under the extreme UV radiation field, as is observed in local metal-poor galaxies and in young compact starbursts. The presence of a type 1 AGN is not supported by the observed SED as the hot dust emission in luminous high- z quasi-stellar objects (QSOs) contributes at wavelengths above rest-frame 1 μm, and an additional ad hoc red source would be required to explain the observed flux excess at 0.66 and 0.86 μm. Additional deep MIRI imaging covering the rest-frame near-IR is needed to confirm the flux detection at 10 μm, and to discriminate between the different hot dust emission in the extreme starburst and AGN scenarios.
Source: Astronomy and Astrophysics
Institutions: Space Telescope Science Institute, Consejo Superior de Investigaciones Científicas, Centro de Astrobiología, European Space Agency, Stockholm University, AlbaNova, Heidelberg University, Max Planck Institute for Astronomy, University of Oxford, European Space Astronomy Centre, University of Copenhagen, University of Arizona, Leiden University, Leiden Observatory, DTU Space, Technical University of Denmark, University of the Pacific, The University of Texas at Austin, Massachusetts Institute of Technology
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Funders: National Aeronautics and Space Administration, Villum Fonden, Comunidad de Madrid, Space Telescope Science Institute, European Commission, Swedish National Space Agency, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Ministerio de Ciencia e Innovación, European Regional Development Fund, Agencia Estatal de Investigación
Awards: G103270039, G121809054, G1338664626, G1519656445, G1622782223, G1638893853, G1700342535, G2121557134, G2144673021, G2237791728, G2309174360, G2423984465, G256731684, G2660406951, G3070465322, G3413939731, G3465966230, G3480869486, G3518538256, G3823816291, G4161023950, G434337789, G4442677895, G4526231891, G4714975165, G4719436119, G5080475149, G5568641063, G5677826004, G5771713820, G7084143925, G7322907961, G7434936867, G7709247530, G8920660035, Fuel Up: How Cold Gas Fuels Star Formation Through Cosmic Time, G897484643
OpenAlex ID: W4417011577