Deciphering the Nature of Virgil: An Obscured Active Galactic Nucleus Lurking within an Apparently Normal Lyα Emitter during Cosmic Reionization
The Astrophysical Journal American Astronomical Society 994:1 (2025) 86
Authors:
Pierluigi Rinaldi, Pablo G Pérez-González, George H Rieke, Jianwei Lyu, Francesco D’Eugenio, Zihao Wu, Stefano Carniani, Tobias J Looser, Irene Shivaei, Leindert A Boogaard, Tanio Diaz-Santos, Luis Colina, Göran Östlin, Stacey Alberts, Javier Álvarez-Márquez, Marianna Annuziatella, Manuel Aravena, Rachana Bhatawdekar, Andrew J Bunker, Karina I Caputi, Stéphane Charlot, Alejandro Crespo Gómez, Mirko Curti, Andreas Eckart, Steven Gillman, Kevin Hainline, Nimisha Kumari, Jens Hjorth, Edoardo Iani, Hanae Inami, Zhiyuan Ji, Benjamin D Johnson, Gareth C Jones, Álvaro Labiano, Roberto Maiolino, Jens Melinder, Thibaud Moutard, Florian Peissker, Marcia Rieke, Brant Robertson, Jan Scholtz, Sandro Tacchella, Paul P van der Werf, Fabian Walter, Christina C Williams, Chris Willott, Joris Witstok, Hannah Übler, Yongda Zhu
Abstract:
We present a comprehensive analysis of the MIRI Extremely Red Object Virgil, a Lyα emitter at zspec = 6.6379 ± 0.0035 with the photometric properties of a Little Red Dot. Leveraging new JWST/MIRI imaging from the MIDIS and PAHSPECS programs, we confirm Virgil’s extraordinary nature among galaxies in JADES/GOODS-South, exhibiting a strikingly red NIRCam-to-MIRI color (F444W–F1500W = 2.84 ± 0.04 mag). Deep NIRSpec/PRISM spectroscopy from the OASIS program offers key insights into the host galaxy, revealing properties of an average star-forming galaxy during Cosmic Reionization, such as a subsolar metallicity, low-to-moderate dust content, and a relatively high ionization parameter and electron temperature. By estimating the star formation rate of Virgil from UV and Hα, we find evidence that the galaxy is either entering or fading out of a bursty episode. Although line-ratio diagnostics employed at high z would classify Virgil as an active galactic nucleus (AGN), this classification becomes ambiguous once redshift evolution is considered. Nonetheless, Virgil occupies the same parameter space as recently confirmed AGNs at similar redshifts. The new deep MIRI data at 15 μm reinforce the AGN nature of Virgil, as inferred from multiple spectral energy distribution (SED) fitting codes. Virgil’s rising infrared SED and UV excess resemble those of Dust-Obscured Galaxies (DOGs) studied with Spitzer at Cosmic Noon, particularly blue-excess HotDOGs. Our results highlight the need for a multiwavelength approach incorporating MIRI to uncover such extreme sources at z ≳ 6 and to shed light on the interplay between galaxy evolution and early black hole growth during Cosmic Reionization.
