Two X-ray Sources in a z~6.2 Quasar/Galaxy Merger. (arXiv:1909.08619v1 [astro-ph.GA])

Two X-ray Sources in a z~6.2 Quasar/Galaxy Merger. (arXiv:1909.08619v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Connor_T/0/1/0/all/0/1">Thomas Connor</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Banados_E/0/1/0/all/0/1">Eduardo Ba&#xf1;ados</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stern_D/0/1/0/all/0/1">Daniel Stern</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Decarli_R/0/1/0/all/0/1">Roberto Decarli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schindler_J/0/1/0/all/0/1">Jan-Torge Schindler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fan_X/0/1/0/all/0/1">Xiaohui Fan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Farina_E/0/1/0/all/0/1">Emanuele Paolo Farina</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mazzucchelli_C/0/1/0/all/0/1">Chiara Mazzucchelli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mulchaey_J/0/1/0/all/0/1">John S. Mulchaey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Walter_F/0/1/0/all/0/1">Fabian Walter</a>

Quasars at early redshifts ($z > 6$) with companion galaxies offer unique
insights into the growth and evolution of the first supermassive black holes.
Here, we report on a 150 ks Chandra observation of PSO J308.0416$-$21.2339, a
$z=6.23$ quasar with a merging companion galaxy identified in [C II] and
rest-frame UV emission. With $72.3^{+9.6}_{-8.6}$ net counts, we find that PSO
J308.0416$-$21.2339 is powerful ($L_X = 2.31^{+1.14}_{-0.76} times 10^{45}
textrm{erg},textrm{s}^{-1},textrm{cm}^{-2}$ in rest frame $2.0-10.0$ keV)
yet soft (spectral power-law index $Gamma=2.39^{+0.37}_{-0.36}$ and
optical-to-X-ray slope $alpha_{rm OX} = -1.41 pm 0.11$). In addition, we
detect three hard-energy photons 2.0 arcseconds to the west of the main quasar,
cospatial with the brightest UV emission of the merging companion. As no soft
energy photons are detected in the same area, this is potentially indicative of
a highly-obscured source. With conservative assumptions, and accounting for
both background fluctuations and the extended wings of the quasar’s emission,
these photons represent a $2.4sigma$ detection. If confirmed by deeper
observations, this system is the first high redshift quasar and companion
individually detected in X-rays and is likely a dual AGN.

Quasars at early redshifts ($z > 6$) with companion galaxies offer unique
insights into the growth and evolution of the first supermassive black holes.
Here, we report on a 150 ks Chandra observation of PSO J308.0416$-$21.2339, a
$z=6.23$ quasar with a merging companion galaxy identified in [C II] and
rest-frame UV emission. With $72.3^{+9.6}_{-8.6}$ net counts, we find that PSO
J308.0416$-$21.2339 is powerful ($L_X = 2.31^{+1.14}_{-0.76} times 10^{45}
textrm{erg},textrm{s}^{-1},textrm{cm}^{-2}$ in rest frame $2.0-10.0$ keV)
yet soft (spectral power-law index $Gamma=2.39^{+0.37}_{-0.36}$ and
optical-to-X-ray slope $alpha_{rm OX} = -1.41 pm 0.11$). In addition, we
detect three hard-energy photons 2.0 arcseconds to the west of the main quasar,
cospatial with the brightest UV emission of the merging companion. As no soft
energy photons are detected in the same area, this is potentially indicative of
a highly-obscured source. With conservative assumptions, and accounting for
both background fluctuations and the extended wings of the quasar’s emission,
these photons represent a $2.4sigma$ detection. If confirmed by deeper
observations, this system is the first high redshift quasar and companion
individually detected in X-rays and is likely a dual AGN.

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