BRIGHT [C ii] AND DUST EMISSION IN THREE z > 6.6 QUASAR HOST GALAXIES OBSERVED BY ALMA

• Published in: The Astrophysical journal 2016-01, Vol.816 (1), p.1-15
• Main Authors: Venemans, Bram P., Walter, Fabian, Zschaechner, Laura, Decarli, Roberto, De Rosa, Gisella, Findlay, Joseph R., McMahon, Richard G., Sutherland, Will J.
• Format: Article
• Language: English
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLACK HOLES; BOLOMETERS; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; Continuums; COSMIC DUST; COSMOLOGY; cosmology: observations; DETECTION; Dust; EMISSION; FLUX DENSITY; Fluxes; GALAXIES; galaxies: active; galaxies: high-redshift; galaxies: individual (VIKING J234833.34-305410.0, J010953.13304726.3, J030516.92-315056.0); LUMINOSITY; MASS; QUASARS; RED SHIFT; ROTATION; Star formation; STARS
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/0004-637X/816/1/37

ABSTRACT We present ALMA detections of the [C ii] 158 m 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 m (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 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 m 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.