The SRG/eROSITA All-Sky Survey: X-ray beacons at late cosmic dawn

Wolf J, Salvato M, Belladitta S, Arcodia R, Ciroi S, Di Mille F, Sbarrato T, Buchner J, Hämmerich S, Wilms J, Collmar W, Dwelly T, Merloni A, Urrutia T, Nandra K (2024)

Publication Type: Journal article

Publication year: 2024

Journal

Astronomy & Astrophysics EDP Sciences

Book Volume: 691

Article Number: A30

DOI: 10.1051/0004-6361/202451035

Abstract

Context. The Spektrum-Roentgen-Gamma (SRG)/extended Roentgen Survey with an Imaging Telescope Array (eROSITA) All-Sky Survey (eRASS) is expected to contain ∼100 quasars that emitted their light when the universe was less than a billion years old, that is, at z > 5.6. By selection, these quasars populate the bright end of the active galactic nuclei (AGN) X-ray luminosity function, and their space density offers a powerful demographic diagnostic of the parent super-massive black hole (SMBH) population. Aims. Of the ≳ 400 quasars that have been discovered at z > 5.6 to date, less than 15% have been X-ray detected. We present a pilot survey to uncover the elusive X-ray luminous end of the distant quasar population. Methods. We have designed a quasar selection pipeline based on optical, infrared and X-ray imaging data from DES DR2, VHS DR5, CatWISE2020 and the eRASS (up to its four-pass cumulative version, eRASS:4). The core selection method relies on SED template fitting. We performed optical follow-up spectroscopy with the Magellan/LDSS3 instrument for the redshift confirmation of a subset of candidates. We have further obtained a deeper X-ray image of one of our candidates with Chandra ACIS-S. Results. We report the discovery of five new quasars in the redshift range 5.6 < z < 6.1. Two of these quasars are detected in eRASS and are, therefore, X-ray ultra-luminous by selection. We also report the detection of these quasars at radio frequencies. The first one is a broad absorption line quasar, which shows significant, order-of-magnitude X-ray dimming over 3.5 years, corresponding to six months in the quasar rest frame. The second X-ray detected quasar is a jetted source with compact morphology. We show that a blazar configuration is likely for this source, making it one of the most distant blazars known to date. Conclusions. With our pilot study, we demonstrate the power of eROSITA as a discovery machine for luminous quasars in the epoch of reionization. The X-ray emission of the two eROSITA detected quasars are likely to be driven by different high-energetic emission mechanisms, a diversity which we will further explore in a future systematic full-hemisphere survey.

Authors with CRIS profile

Steven Hämmerich Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut Jörn Wilms Professur für Astronomie und Astrophysik

Involved external institutions

Max-Planck-Institut für Astronomie / Max Planck Institute for Astronomy (MPIA) DE Germany (DE) Max-Planck-Institut für extraterrestrische Physik (MPE) / Max Planck Institute for Extraterrestrial Physics DE Germany (DE) University of Padua / Universita degli Studi di Padova IT Italy (IT) Las Campanas Observatory (LCO) CL Chile (CL) National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF) IT Italy (IT) Leibniz Institute for Astrophysics Potsdam / Leibniz-Institut für Astrophysik Potsdam DE Germany (DE)

How to cite

APA:

Wolf, J., Salvato, M., Belladitta, S., Arcodia, R., Ciroi, S., Di Mille, F.,... Nandra, K. (2024). The SRG/eROSITA All-Sky Survey: X-ray beacons at late cosmic dawn. Astronomy & Astrophysics, 691. https://doi.org/10.1051/0004-6361/202451035

MLA:

Wolf, J., et al. "The SRG/eROSITA All-Sky Survey: X-ray beacons at late cosmic dawn." Astronomy & Astrophysics 691 (2024).

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