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Abstract The identification of bright quasars atz≳ 6 enables detailed studies of supermassive black holes, massive galaxies, structure formation, and the state of the intergalactic medium within the first billion years after the Big Bang. We present the spectroscopic confirmation of 55 quasars at redshifts 5.6 <z< 6.5 and UV magnitudes −24.5 <M1450< −28.5 identified in the optical Pan-STARRS1 and near-IR VIKING surveys (48 and 7, respectively). Five of these quasars have independently been discovered in other studies. The quasar sample shows an extensive range of physical properties, including 17 objects with weak emission lines, 10 broad absorption line quasars, and 5 objects with strong radio emission (radio-loud quasars). There are also a few notable sources in the sample, including a blazar candidate atz= 6.23, a likely gravitationally lensed quasar atz= 6.41, and az= 5.84 quasar in the outskirts of the nearby (D∼ 3 Mpc) spiral galaxy M81. The blazar candidate remains undetected in NOEMA observations of the [Cii]and underlying emission, implying a star formation rate <30–70M⊙yr−1. A significant fraction of the quasars presented here lies at the foundation of the first measurement of thez∼ 6 quasar luminosity function from Pan-STARRS1 (introduced in a companion paper). These quasars will enable further studies of the high-redshift quasar population with current and future facilities.
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This content will become publicly available on July 1, 2027
Euclid : A UV-faint quasar in a highly luminous star-forming host galaxy at z ≈ 7.7
Constraining the co-evolution of supermassive black holes and their host galaxies in the first billion years after the Big Bang is essential for understanding the formation of the earliest cosmic structures. Here, we present IRAM/NOrthern Extended Millimeter Array (NOEMA) observations of thez ≈ 7.7 quasar EUCL J125308.55+705432.3, recently discovered in the first data release of the Euclid Wide Survey. We report the most distant detections of [C II]158 μm and cold dust emission in a quasar host to date. The [C II]emission line sets the systemic redshift atz = 7.6980 ± 0.0004. The source exhibits luminosities ofLFIR = 3.6 × 1012 L⊙andL[C II]= 2 × 109L⊙, respectively, a dust mass of 1.4 × 108 M⊙, and a dynamical mass in the range 0.33 − 1.3 × 1010 M⊙. Remarkably, despite being nearly two magnitudes fainter in the rest-frame UV (M1450 = −24.06) than previously knownz ≈ 7.5 quasars (⟨M1450⟩ ∼ − 26.5), EUCL J125308.55+705432.3 exhibits the brightest [C II]emission among them. This indicates that the host galaxy is actively star-forming, with a star-formation rate > 250M⊙yr−1, consistent with recent findings that UV-faint quasars atz > 6 preferentially reside in [C II]-luminous galaxies. The UV-faintness likely reflects dust obscuration or sub-Eddington accretion, rather than lower host mass, suggesting these systems are at a different stage in their evolution compared to UV-bright quasars. These IRAM/NOEMA observations highlight the power of combiningEuclid’s wide-area quasar discovery potential with submillimetre follow-up observations to characterise the host galaxies of early supermassive black holes across a broader redshift and luminosity range than previously accessible.
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- Award ID(s):
- 2513040
- PAR ID:
- 10705320
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- A&A
- Date Published:
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 711
- ISSN:
- 0004-6361
- Page Range / eLocation ID:
- A150
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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