Bright [C II] and Dust Emission in Three z > 6.6 Quasar Host Galaxies Observed by ALMA

Journal
Date Issued
2016
Author(s)
Venemans, Bram P.
•
Walter, Fabian
•
Zschaechner, Laura
•
•
De Rosa, Gisella
•
Findlay, Joseph R.
•
McMahon, Richard G.
•
Sutherland, Will J.
DOI
Abstract
We present ALMA detections of the [C II] 158 μm emission line and the underlying far-infrared (FIR) continuum of three quasars at 6.6 < z < 6.9 selected from the VIKING survey. The [C II] line fluxes range between 1.6 and 3.4 Jy km s-1 ([C II] luminosities ∼(1.9-3.9) × 109 L☉). We measure continuum flux densities of 0.56-3.29 mJy around 158 μm (rest frame), with implied FIR luminosities of (0.6-7.5) × 1012 L☉ and dust masses Md = (0.7-24) × 108 M☉. In one quasar we derive a dust temperature of {30}-9+12 K from the continuum slope, below the canonical value of 47 K. Assuming that the [C II] and continuum emission are powered by star formation, we find star formation rates from 100 to 1600 M☉ yr-1 based on local scaling relations. The L[C II]/LFIR ratios in the quasar hosts span a wide range from (0.3-4.6) × 10-3, including one quasar with a ratio that is consistent with local star-forming galaxies. We find that the strength of the L[C II] and 158 μm continuum emission in z ≳ 6 quasar hosts correlates with the quasar’s bolometric luminosity. In one quasar, the [C II] line is significantly redshifted by ∼1700 km s-1 with respect to the Mg II broad emission line. Comparing to values in the literature, we find that, on average, the Mg II is blueshifted by 480 km s-1 (with a standard deviation of 630 km s-1) with respect to the host galaxy redshift, I.e., one of our quasars is an extreme outlier. Through modeling we can rule out a flat rotation curve for our brightest [C II] emitter. Finally, we find that the ratio of black hole mass to host galaxy (dynamical) mass is higher by a factor of 3-4 (with significant scatter) than local relations.
Volume
816
Issue
1
Start page
37
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...816...37V
Rights
open.access
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