Misc,
Bright CII and dust emission in three z>6.6 quasar host galaxies observed by ALMA
(2015)cite arxiv:1511.07432Comment: 16 pages, 12 figures. Accepted for publication in ApJ.
Abstract
We present ALMA detections of the CII 158 micron emission line and the
underlying far-infrared continuum of three quasars at 6.6<z<6.9 selected from
the VIKING survey. The CII line fluxes range between 1.6-3.4 Jy km/s (CII
luminosities ~(1.9-3.9)x10^9 L_sun). We measure continuum flux densities of
0.56-3.29 mJy around 158 micron (rest-frame), with implied far-infrared
luminosities between (0.6-7.5)x10^12 L_sun and dust masses M_d=(0.7-24)x10^8
M_sun. In one quasar we derive a dust temperature of 30^+12_-9 K from the
continuum slope, below the canonical value of 47 K. Assuming that the CII and
continuum emission are powered by star formation, we find star-formation rates
from 100-1600 M_sun/yr based on local scaling relations. The L_CII/L_FIR
ratios in the quasar hosts span a wide range from (0.3-4.6)x10^-3, including
one quasar with a ratio that is consistent with local star-forming galaxies. We
find that the strength of the L_CII and 158 micron continuum emission in z>~6
quasar hosts correlate with the quasar's bolometric luminosity. In one quasar,
the CII line is significantly redshifted by ~1700 km/s with respect to the
MgII broad emission line. Comparing to values in the literature, we find that,
on average, the MgII is blueshifted by 480 km/s (with a standard deviation of
630 km/s) 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 CII emitter. Finally, we find that the ratio of black hole mass
to host galaxy (dynamical) mass is higher by a factor 3-4 (with significant
scatter) than local relations.
