Radio Quasars in the Cosmic Dawn: A Spectroscopic Sample from the DESI Survey
Abstract
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 Spectroscopic Instrument 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 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 4400Å > 10). With radio luminosities of ∼10 25−28 W Hz −1 , the radio emission in all 83 quasars is expected to be jet dominated rather than powered by star formation. Analysis of their rest-frame ultraviolet spectra reveals broadly similar composite spectral properties and C iv velocity shifts compared to radio-nondetected quasars. The radio-detected and radio-loud quasars exhibit slightly smaller Ly α and C iv equivalent widths on average; however, we find no significant evidence (∼1.3 σ ) for a higher fraction of weak-line quasars (∼10% ± 4% versus ∼4% ± 1% for radio-nondetected 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 is a physically distinct phenomenon. Our results demonstrate that powerful radio jets were already well established by z ∼ 5.
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Authors: A. J. Gloudemans, Jinyi Yang, David M. Alexander, Dey Arjun, Xiaohui Fan, Victoria A. Fawcett, M. J. Hardcastle, Stephanie Juneau, GEORGE K. MILEY, Leah K. Morabito, Adam D. Myers, Swayamtrupta Panda, Huub J. A. Röttgering, Timothy Shimwell, Daniel J. B. Smith, Feige Wang, J. A. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. Cuceu, A. de la Macorra, P. Doel, S. Ferraro, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutierrez, C. Hahn, M. Ishak, R. Joyce, R. Kehoe, D. Kirkby, T. Kisner, A. Kremin, Martin Landriau, L. Le Guillou, M. E. Levi, M. Manera, Aaron Meisner, R. Miquel, J. Moustakas, S. Nadathur, W. J. Percival, F. Prada, I. Pérez-Ràfols, A. Robertson, G. Rossi, E. Sanchez, Edward F. Schlafly, D. Schlegel, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou, H. Zou
Institutions: Universidad Nacional Autónoma de México, Chinese Academy of Sciences, University of Virginia, University of Michigan, Boston University, Consejo Superior de Investigaciones Científicas, University College London, Universitat Autònoma de Barcelona, University of Arizona, Sorbonne Université, University of Waterloo, Institució Catalana de Recerca i Estudis Avançats, University of California, Berkeley, Durham University, University of California, Irvine, University of Wyoming, Universitat Politècnica de Catalunya, Newcastle University, University of Milan, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, University of Hertfordshire, University of Portsmouth, The University of Texas at Dallas, Sejong University, Leiden University, Lawrence Berkeley National Laboratory, Fermi National Accelerator Laboratory, University of Siena, Institut d'Estudis Espacials de Catalunya, NSF NOIRLab, Southern Methodist University, Netherlands Institute for Radio Astronomy, Instituto de Astrofísica de Andalucía, National Institute for Astrophysics, Universidad de Los Andes, Space Telescope Science Institute, Brera Astronomical Observatory, Institute for High Energy Physics, Perimeter Institute, International Gemini Observatory