English

A quasar hatching from a buried red phase at z = 3.7

Astrophysics of Galaxies 2026-07-25 v1

Abstract

We present JADES-GS 209777, previously cataloged as CANDELS J033238.02-274626.2, hereafter "the Hatchling," a red quasar at z=3.711z=3.711. While the source has been reported in earlier deep-field catalogs, our multiwavelength analysis reveals a visible active nucleus still embedded in a dense gas- and dust-rich environment. Red quasar continua are often attributed to dust attenuation, including non-standard extinction curves, but the highly comprehensive multiwavelength data for this source provide direct constraints on the material being cleared. Using JWST/NIRSpec, NIRCam, MIRI, HST, MUSE, Chandra, ALMA, and VLA data, we detect broad emission lines and strong X-ray emission, showing that the active nucleus is at least partially exposed. We also detect Hα\alpha and He I absorption, indicating dense gas close to the nucleus. Kinematically disturbed O I, Mg II, Na D, and [O III] features, together with extended Lyα\alpha emission over 20\gtrsim 20 kpc, further show that multiphase gas is being accelerated from the nuclear region into the host-galaxy environment. The ALMA detection reveals strong dust emission, with the inferred infrared luminosity placing the system in the ULIRG regime. The continuum is red and sharply declining toward the rest-frame UV, resembling compact red AGNs, and may reflect extreme dust attenuation, gas reprocessing, possible BAL-like absorption, or a combination of these effects. Regardless of which mechanism dominates the continuum shape, the line diagnostics show that the visible nucleus remains partially obscured by nearby material. The Hatchling therefore represents a unique opportunity to explore a poorly known transition phase in which feedback is likely clearing an enshrouded quasar and allowing it to emerge toward a more unobscured active nucleus.

Keywords

Cite

@article{arxiv.2607.22966,
  title  = {A quasar hatching from a buried red phase at z = 3.7},
  author = {Zheng Ma and Yongda Zhu and Zhiyuan Ji and Eiichi Egami and Marcia J. Rieke and Xiaohui Fan and Jianwei Lyu and George H. Rieke and Fengwu Sun and Yang Sun and George D. Becker and Andrew J. Bunker and Francesco D'Eugenio and Xiangyu Jin and Ignas Juodžbalis and Weizhe Liu and Roberto Maiolino and Pierluigi Rinaldi and Feige Wang and Christopher N. A. Willmer and Yunjing Wu and Jinyi Yang and Junyu Zhang and Peixin Zhu},
  journal= {arXiv preprint arXiv:2607.22966},
  year   = {2026}
}

Comments

26 pages, 5 main figures, and 10 Extended Data figures. Submitted, comments are welcome