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The Compact, ∼1 kpc Host Galaxy of a Quasar at a Redshift of 7.1

Venemans, Bram P. and Walter, Fabian and Decarli, Roberto and Bañados, Eduardo and Hodge, Jacqueline and Hewett, Paul and McMahon, Richard G. and Mortlock, Daniel J. and Simpson, Chris (2017) The Compact, ∼1 kpc Host Galaxy of a Quasar at a Redshift of 7.1. Astrophysical Journal, 837 (2). Art. No. 146. ISSN 1538-4357. doi:10.3847/1538-4357/aa62ac.

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We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [C II] fine-structure line and the underlying far-infrared (FIR) dust continuum emission in J1120+0641, the most distant quasar currently known (z = 7.1). We also present observations targeting the CO(2–1), CO(7–6), and [C I] 369 μm lines in the same source obtained at the Very Large Array and Plateau de Bure Interferometer. We find a [C II] line flux of F_[C II] = 1.11 ± 0.10 Jy km s^(-1) and a continuum flux density of S_(227 GHz) = 0.53 ± 0.04 mJy beam^(−1), consistent with previous unresolved measurements. No other source is detected in continuum or [C II] emission in the field covered by ALMA (~ 25''). At the resolution of our ALMA observations (0.”23, or 1.2 kpc, a factor of ~70 smaller beam area compared to previous measurements), we find that the majority of the emission is very compact: a high fraction (~80%) of the total line and continuum flux is associated with a region 1–1.5 kpc in diameter. The remaining ~20% of the emission is distributed over a larger area with radius ≾4 kpc. The [C II] emission does not exhibit ordered motion on kiloparsec scales: applying the virial theorem yields an upper limit on the dynamical mass of the host galaxy of (4.3 ± 0.9) x 10^(10)M⊙, only ~20 × higher than the central black hole (BH). The other targeted lines (CO(2–1), CO(7–6), and [C I]) are not detected, but the limits of the line ratios with respect to the [C II] emission imply that the heating in the quasar host is dominated by star formation, and not by the accreting BH. The star formation rate (SFR) implied by the FIR continuum is 105–340 M⊙ yr(-1), with a resulting SFR surface density of ~100–350 M⊙ yr(-1) kpc^(−2), well below the value for Eddington-accretion-limited star formation.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Venemans, Bram P.0000-0001-9024-8322
Walter, Fabian0000-0003-4793-7880
Decarli, Roberto0000-0002-2662-8803
Bañados, Eduardo0000-0002-2931-7824
Hodge, Jacqueline0000-0001-6586-8845
Alternate Title:The compact, ~1 kpc host galaxy of a quasar at z = 7.1
Additional Information:© 2017 The American Astronomical Society. Received 2016 December 16; revised 2017 February 10; accepted 2017 February 12; published 2017 March 15. We thank the referee for providing valuable comments and suggestions. B.P.V. and F.W. 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." P.C.H. and R.G.M. acknowledge the support of the UK Science and Technology Facilities Council (STFC) through the award of a Consolidated Grant to the Institute of Astronomy. We thank Rowin Meijerink for help with the modeling of the line ratios. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2012.1.00882.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. Based in part on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Facilities: ALMA, IRAM:Interferometer, EVLA.
Funding AgencyGrant Number
European Research Council (ERC)Cosmic Dawn
Deutsche Forschungsgemeinschaft (DFG)1573
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords:cosmology: observations – galaxies: active – galaxies: high-redshift – galaxies: individual (ULAS J112001.48+064124.3) – galaxies: ISM
Issue or Number:2
Record Number:CaltechAUTHORS:20170314-101008186
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Official Citation:Bram P. Venemans et al 2017 ApJ 837 146
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75089
Deposited By: Tony Diaz
Deposited On:15 Mar 2017 18:43
Last Modified:15 Nov 2021 16:30

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