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Published December 10, 2017 | Published
Journal Article Open

Copious Amounts of Dust and Gas in a z = 7.5 Quasar Host Galaxy

Abstract

We present IRAM/NOEMA and JVLA observations of the quasar J1342+0928 at z = 7.54 and report detections of copious amounts of dust and [C II] emission in the interstellar medium (ISM) of its host galaxy. At this redshift, the age of the universe is 690 Myr, about 10% younger than the redshift of the previous quasar record holder. Yet, the ISM of this new quasar host galaxy is significantly enriched by metals, as evidenced by the detection of the [C II] 158 μm cooling line and the underlying far-infrared (FIR) dust continuum emission. To the first order, the FIR properties of this quasar host are similar to those found at a slightly lower redshift (z ~ 6), making this source by far the FIR-brightest galaxy known at z ≳ 7.5. The [C II] emission is spatially unresolved, with an upper limit on the diameter of 7 kpc. Together with the measured FWHM of the [C II] line, this yields a dynamical mass of the host of <1.5 x 10^(11) M⊙. Using standard assumptions about the dust temperature and emissivity, the NOEMA measurements give a dust mass of (0.6-4.3 x 10^8 M⊙. The brightness of the [C II] luminosity, together with the high dust mass, imply active ongoing star formation in the quasar host. Using [C II]–SFR scaling relations, we derive star formation rates of 85–545 M⊙ yr^(−1) in the host, consistent with the values derived from the dust continuum. Indeed, an episode of such past high star formation is needed to explain the presence of ~10^8 M⊙ of dust implied by the observations.

Additional Information

© 2017 The American Astronomical Society. Received 2017 August 29; revised 2017 October 13; accepted 2017 October 17; published 2017 December 6. We thank the referee for providing valuable comments and suggestions. B.P.V., F.W., and E.P.F. acknowledge funding through the ERC grant "Cosmic Dawn." Support for R.D. was provided by the DFG priority program 1573 "The physics of the interstellar medium." We thank Amanda Karakas for help with estimating the metal production in stars. We are grateful to the JVLA and NOEMA for providing DDT observations. This work is based on observations carried our under project number E16AH with the IRAM NOEMA Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

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August 19, 2023
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