GA-NIFS: Black hole and host galaxy properties of two z ≃ 6.8 quasars from the NIRSpec IFU

¹ National Research Council of Canada, Herzberg Astronomy & Astrophysics Research Centre, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
e-mail: madeline_marshall@outlook.com
² ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Stromlo, Australia
³ Centro de Astrobiología (CAB), CSIC-INTA, Ctra. de Ajalvir km 4, Torrejón de Ardoz, 28850 Madrid, Spain
⁴ Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁵ Cavendish Laboratory – Astrophysics Group, University of Cambridge, 19 JJ Thomson Avenue, Cambridge CB3 0HE, UK
⁶ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁷ Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
⁸ European Space Agency, c/o STScI, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁹ Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
¹⁰ Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis Bd Arago, 75014 Paris, France
¹¹ European Space Agency, ESAC, Villanueva de la Cañada, 28692 Madrid, Spain
¹² Cosmic Dawn Center (DAWN), Copenhagen, Denmark
¹³ Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen, Denmark
¹⁴ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹⁵ INAF – Osservatorio Astrofisco di Arcetri, Largo E. Fermi 5, 50127 Firenze, Italy
¹⁶ Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield AL10 9AB, UK
¹⁷ AURA for the European Space Agency, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁸ Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA

Received: 7 February 2023
Accepted: 26 August 2023

Abstract

Aims. Integral field spectroscopy (IFS) with JWST NIRSpec will significantly improve our understanding of the first quasars, by providing spatially resolved, infrared spectroscopic capabilities that cover key rest-frame optical emission lines that have been previously unobservable.

Methods. Here we present our results from the first two z > 6 quasars observed as a part of the Galaxy Assembly with NIRSpec IFS (GA-NIFS) GTO programme, with DELS J0411–0907 at z = 6.82 and VDES J0020–3653 at z = 6.86.

Results. By observing the Hβ, [O III] λλ4959, 5007, and Hα emission lines in these high-z quasars for the first time, we measured accurate black hole masses, M_BH = 1.85_−0.8⁺² × 10⁹ M_⊙ and 2.9_−1.3^+3.5 × 10⁹M_⊙, corresponding to Eddington ratios of λ_Edd = 0.8_−0.4^+0.7 and 0.4_−0.2^+0.3 for DELS J0411–0907 and VDES J0020–3653, respectively. These provide a key comparison for existing estimates from the more uncertain Mg II line. We performed quasar–host decomposition using models of the quasars’ broad lines to measure the underlying host galaxies. We also discovered multiple emission line regions surrounding each of the host galaxies, which are likely companion galaxies undergoing mergers with these hosts. We measured the star formation rates, excitation mechanisms, and dynamical masses of the hosts and companions, measuring the M_BH/M_dyn ratios at high z using these estimators for the first time. DELS J0411–0907 and VDES J0020–3653 both lie above the local black hole–host mass relation, and are consistent with the existing observations of z ≳ 6 quasar host galaxies with ALMA. We detected ionised outflows in [O III] λλ4959, 5007 and Hβ from both quasars, with mass outflow rates of 58₋₃₇⁺⁴⁴ and 525₋₉₂⁺⁷⁵ M_⊙ yr⁻¹ for DELS J0411–0907 and VDES J0020–3653, much larger than their host star formation rates of < 33 and < 54 M_⊙ yr⁻¹, respectively.

Conclusions. This work highlights the exceptional capabilities of the JWST NIRSpec IFU for observing quasars in the early Universe.