Abstract
The CII 158$\mu$m fine-structure line is known to trace regions of active
star formation and is the main coolant of the cold, neutral atomic medium. In
this Letter, we report a strong detection of the CII line in the
host galaxy of the brightest quasar known at $z>6.5$, the Pan-STARRS1 selected
quasar PSO J036.5078+03.0498 (hereafter P036+03), using the IRAM NOEMA
millimeter interferometer. Its CII and total far-infrared luminosities are
$(5.8 0.7) 10^9 \,L_ødot$ and $(7.6\pm1.5) \times
10^12\,L_ødot$, respectively. This results in a $L_CII /L_TIR$ ratio
of $0.810^-3$, which is at the high end for those found for
active galaxies, though it is lower than the average found in typical main
sequence galaxies at $z0$. We also report a tentative additional line
which we identify as a blended emission from the $3_22 - 3_13$ and $5_23
- 4_32$ H$_2$O transitions. If confirmed, this would be the most distant
detection of water emission to date. P036+03 rivals the current prototypical
luminous J1148+5251 quasar at $z=6.42$, in both rest-frame UV and CII
luminosities. Given its brightness and because it is visible from both
hemispheres (unlike J1148+5251), P036+03 has the potential of becoming an
important laboratory for the study of star formation and of the interstellar
medium only $800\,$Myr after the Big Bang.
Description
[1504.05216] Bright [CII] 158$\mu$m emission in a quasar host galaxy at $z=6.54$
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