Radio Quasars in the Cosmic Dawn: A Spectroscopic Sample from the DESI Survey
Abstract
We present the largest statistical spectroscopic sample of radio quasars at 4.7<z<6.7 to date. These have been selected from a dedicated Dark Energy Survey Instrument (DESI) target program and provide a robust sample to study the influence of radio jets on early quasar evolution. Using low-frequency radio data from the LOFAR Two Metre Sky Survey Data Release 3 (LoTSS-DR3) at 144 MHz, we identify 83 high-z radio quasars, 26 of which are classified as radio-loud (5-15% of 646 confirmed high-z quasars, defined as R = F5GHz/F4400A >10). With radio luminosities of ∼1025−28 W/Hz, the radio emission in all 83 quasars is expected to be jet-dominated rather than powered by star formation. Analysis of their rest-frame ultra-violet (UV) spectra reveals broadly similar composite spectral properties and CIV velocity shifts compared to radio non-detected quasars. The radio-detected and radio-loud quasars exhibit slightly smaller Lyα and CIV equivalent widths on average, however, we find no significant evidence (∼1.3σ) for a higher fraction of weak-line quasars (WLQs; ~10+/-4% versus ~4+/-1% for radio non-detected quasars). We further find that the broad absorption line (BAL) quasars are predominantly radio-quiet, and no correlation is observed between absorption index and radio-loudness, suggesting that radio emission is not produced by the BAL outflows themselves and are physically distinct phenomena. Our results demonstrate that powerful radio jets were already well-established by z~5.
Related
- Nitrogen-Loud Quasars from the Dark Energy Spectroscopic Instrument. I. Sample Selection and Basic Properties
- Extreme Enrichment at Cosmic Dawn: Three FeII-Strong Quasars at z > 6 from the JWST Aether survey
- Extreme Enrichment at Cosmic Dawn: Three Fe II -strong Quasars at z > 6 from the JWST Aether Survey
- Nitrogen-Loud Quasars from the Dark Energy Spectroscopic Instrument. II. Broad-Line Region Metallicity and Relative Nitrogen Enrichment
- Observational Evidence of Positive Feedback from Radio Quasars
BibTeX
@misc{gloudemans2026radio,
title = {{Radio Quasars in the Cosmic Dawn: A Spectroscopic Sample from the DESI Survey}},
author = {Anniek J Gloudemans and Jinyi Yang and David M Alexander and Arjun Dey and Xiaohui Fan and Victoria A Fawcett and Martin J Hardcastle and Stephanie Juneau and George K Miley and Leah K Morabito and Adam D Myers and Swayamtrupta Panda and Huub J.A Röttgering and Timothy Shimwell and Daniel J.B Smith and Feige Wang and J Aguilar and S Ahlen and D Bianchi and D Brooks and T Claybaugh and A Cuceu and A de la Macorra and P Doel and S Ferraro and J.E Forero-Romero and E Gaztañaga and S Gontcho A. Gontcho and G Gutierrez and C Hahn and M Ishak and R Joyce and R Kehoe and D Kirkby and T Kisner and A Kremin and M Landriau and L Le Guillou and M.E Levi and M Manera and A Meisner and R Miquel and J Moustakas and S Nadathur and W.J Percival and F Prada and I Pérez-Ràfols and A Robertson and G Rossi and E Sanchez and E.F Schlafly and D Schlegel and J Silber and D Sprayberry and G Tarlé and B.A Weaver and R Zhou and H Zou},
howpublished = {HAL},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.26931},
eprint = {2609.26931},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05841977v1},
}
RIS
TY - UNPB
TI - Radio Quasars in the Cosmic Dawn: A Spectroscopic Sample from the DESI Survey
AU - Anniek J Gloudemans
AU - Jinyi Yang
AU - David M Alexander
AU - Arjun Dey
AU - Xiaohui Fan
AU - Victoria A Fawcett
AU - Martin J Hardcastle
AU - Stephanie Juneau
AU - George K Miley
AU - Leah K Morabito
AU - Adam D Myers
AU - Swayamtrupta Panda
AU - Huub J.A Röttgering
AU - Timothy Shimwell
AU - Daniel J.B Smith
AU - Feige Wang
AU - J Aguilar
AU - S Ahlen
AU - D Bianchi
AU - D Brooks
AU - T Claybaugh
AU - A Cuceu
AU - A de la Macorra
AU - P Doel
AU - S Ferraro
AU - J.E Forero-Romero
AU - E Gaztañaga
AU - S Gontcho A. Gontcho
AU - G Gutierrez
AU - C Hahn
AU - M Ishak
AU - R Joyce
AU - R Kehoe
AU - D Kirkby
AU - T Kisner
AU - A Kremin
AU - M Landriau
AU - L Le Guillou
AU - M.E Levi
AU - M Manera
AU - A Meisner
AU - R Miquel
AU - J Moustakas
AU - S Nadathur
AU - W.J Percival
AU - F Prada
AU - I Pérez-Ràfols
AU - A Robertson
AU - G Rossi
AU - E Sanchez
AU - E.F Schlafly
AU - D Schlegel
AU - J Silber
AU - D Sprayberry
AU - G Tarlé
AU - B.A Weaver
AU - R Zhou
AU - H Zou
PY - 2026
DA - 2026/09/22
PB - HAL
DO - 10.48550/arxiv.2609.26931
UR - https://hal.science/hal-05841977v1
AB - We present the largest statistical spectroscopic sample of radio quasars at 4.7<z<6.7 to date. These have been selected from a dedicated Dark Energy Survey Instrument (DESI) target program and provide a robust sample to study the influence of radio jets on early quasar evolution. Using low-frequency radio data from the LOFAR Two Metre Sky Survey Data Release 3 (LoTSS-DR3) at 144 MHz, we identify 83 high-z radio quasars, 26 of which are classified as radio-loud (5-15% of 646 confirmed high-z quasars, defined as R = F_5GHz/F_4400A >10). With radio luminosities of ∼10^25−28 W/Hz, the radio emission in all 83 quasars is expected to be jet-dominated rather than powered by star formation. Analysis of their rest-frame ultra-violet (UV) spectra reveals broadly similar composite spectral properties and CIV velocity shifts compared to radio non-detected quasars. The radio-detected and radio-loud quasars exhibit slightly smaller Lyα and CIV equivalent widths on average, however, we find no significant evidence (∼1.3σ) for a higher fraction of weak-line quasars (WLQs; ~10+/-4% versus ~4+/-1% for radio non-detected quasars). We further find that the broad absorption line (BAL) quasars are predominantly radio-quiet, and no correlation is observed between absorption index and radio-loudness, suggesting that radio emission is not produced by the BAL outflows themselves and are physically distinct phenomena. Our results demonstrate that powerful radio jets were already well-established by z~5.
ER -