MIDIS: MIRI Uncovers Virgil, the First Little Red Dot with Clear Detection of Its Host Galaxy at z ≃ 6.6

MIDIS: MIRI Uncovers Virgil, the First Little Red Dot with Clear Detection of Its Host Galaxy at z ≃ 6.6

We present Virgil, a Mid-Infrared Instrument (MIRI) extremely red object detected with the F1000W filter as part of the MIRI Deep Imaging Survey observations of the Hubble Ultra Deep Field. Virgil is an Ly α emitter (LAE) at z _spec  = 6.6312 ± 0.0019 (from the Very Large Telescope/MUSE) with a rest...

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Main Authors: Edoardo Iani, Pierluigi Rinaldi, Karina I. Caputi, Marianna Annunziatella, Danial Langeroodi, Jens Melinder, Pablo G. Pérez-González, Javier Álvarez-Márquez, Leindert A. Boogaard, Sarah E. I. Bosman, Luca Costantin, Thibaud Moutard, Luis Colina, Göran Östlin, Thomas R. Greve, Gillian Wright, Almudena Alonso-Herrero, Arjan Bik, Steven Gillman, Alejandro Crespo Gómez, Jens Hjorth, Sarah Kendrew, Alvaro Labiano, John P. Pye, Tuomo V. Tikkanen, Fabian Walter, Manuel Güdel, Thomas Henning, Paul P. van der Werf
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal
Subjects:
Galaxy formation
Galaxy evolution
High-redshift galaxies
Stellar populations
Active galactic nuclei
Galaxy ages
Online Access:https://doi.org/10.3847/1538-4357/ade5a6
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Summary:We present Virgil, a Mid-Infrared Instrument (MIRI) extremely red object detected with the F1000W filter as part of the MIRI Deep Imaging Survey observations of the Hubble Ultra Deep Field. Virgil is an Ly α emitter (LAE) at z _spec  = 6.6312 ± 0.0019 (from the Very Large Telescope/MUSE) with a rest-frame UV-to-optical spectral energy distribution (SED) typical of LAEs at similar redshifts. However, MIRI observations reveal an unexpected extremely red color at rest-frame near-infrared (NIR) wavelengths, F444W − F1000W = 2.33 ± 0.06. Such a steep rise in the NIR, completely missed without MIRI imaging, is poorly reproduced by models including only stellar populations and hints toward the presence of an active galactic nucleus, although alternative explanations such as extreme dust obscuration and strong nebular continuum and emission lines contribution due to young stellar ages cannot be completely ruled out. According to the shape of its overall SED, Virgil belongs to the recently discovered population of little red dots but displays an extended rest-frame UV-optical wavelength morphology following a 2D-Sérsic profile with an average index of $n=0.9{3}_{-0.31}^{+0.85}$ and ${r}_{e}=0.4{9}_{-0.11}^{+0.05}$ pkpc. Only at MIRI wavelengths, Virgil is unresolved due to the coarser point-spread function. This discovery demonstrates the crucial importance of deep MIRI surveys to reveal the true nature and properties of high- z galaxies that otherwise would be misinterpreted and raises the question of how common Virgil-like objects could be in the early Universe.
ISSN:1538-4357

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