XQR-30: Black hole masses and accretion rates of 42 z  ≳  6 quasars

¹ Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Avenida Ejercito Libertador 441, Santiago, Chile
e-mail: chiara.mazzucchelli@mail.udp.cl
² INAF – Osservatorio Astronomico di Trieste, Via G.B. Tiepolo, 11, 34143 Trieste, Italy
³ Scuola Normale Superiore, P.zza dei Cavalieri 7, 56126 Pisa, Italy
⁴ IFPU – Institute for Fundamental Physics of the Universe, Via Beirut 2, 34151 Trieste, Italy
⁵ Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
⁶ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR China
⁷ Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), The University of Tokyo, Chiba 277-8583, Japan
⁸ Max Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁹ Department of Physics & Astronomy, University of California, Riverside, CA 92521, USA
¹⁰ ESO, Vitacura Alonso de Córdova 3107, Vitacura, Casilla, 19001 Santiago de Chile, Chile
¹¹ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
¹² MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
¹³ Gemini Observatory, NSF’s NOIRLab, 670 N A’ohoku Place, Hilo, HI 96720, USA
¹⁴ Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia
¹⁵ Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
¹⁶ Steward Observatory, University of Arizona, 933 N Cherry Avenue, Tucson, AZ 85721, USA

Received: 3 March 2023
Accepted: 17 June 2023

Abstract

We present bolometric luminosities, black hole masses, and Eddington ratios for 42 luminous quasars at z ≳ 6 using high signal-to-noise ratio VLT/X-shooter spectra, acquired as part of the enlarged ESO Large Programme XQR-30. In particular, we derived the bolometric luminosities from the rest-frame 3000 Å luminosities using a bolometric correction from the literature, as well as the black hole masses by modeling the spectral regions around the C IV 1549 Å and the Mg II 2798 Å emission lines, with scaling relations calibrated in the Local Universe. We find that the black hole masses derived from both emission lines are in the same range and the scatter of the measurements agrees with expectations from the scaling relations. The Mg II-derived masses are between ∼(0.8−12) ×10⁹ M_⊙ and the derived Eddington ratios are within ∼0.13−1.73, with a mean (median) of 0.84(0.72). By comparing the total sample of quasars at z > 5.8, from this work and from the literature, to a bolometric luminosity distribution-matched sample at z ∼ 1.5, we find that quasars at high redshift host slightly less massive black holes, which accrete slightly more rapidly than those at lower z, with a difference in the mean Eddington ratios of the two samples of ∼0.27. These findings are in agreement with the results of recent works in the literature.