Neutral carbon and highly excited CO in a massive star-forming main sequence galaxy at z=2.2. (arXiv:1907.04936v1 [astro-ph.GA])

Neutral carbon and highly excited CO in a massive star-forming main sequence galaxy at z=2.2. (arXiv:1907.04936v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Brisbin_D/0/1/0/all/0/1">Drew Brisbin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aravena_M/0/1/0/all/0/1">Manuel Aravena</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Daddi_E/0/1/0/all/0/1">Emanuele Daddi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dannerbauer_H/0/1/0/all/0/1">Helmut Dannerbauer</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:+Gonzalez_Lopez_J/0/1/0/all/0/1">Jorge Gonz&#xe1;lez-L&#xf3;pez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Riechers_D/0/1/0/all/0/1">Dominik Riechers</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wagg_J/0/1/0/all/0/1">Jeff Wagg</a>

We used the Plateau De Bure Interferometer to observe multiple CO and neutral
carbon transitions in a z=2.2 main sequence disk galaxy, BX610. Our observation
of CO(7-6), CO(4-3), and both far-infrared(FIR) [CI] lines complements previous
observations of H$alpha$ and low-J CO, and reveals a galaxy that is vigorously
forming stars with UV fields (Log($G$ G$_0^{-1}) lesssim3.25);$ although less
vigorously than local ultra-luminous infrared galaxies or most starbursting
submillimeter galaxies in the early universe. Our observations allow new
independent estimates of the cold gas mass which indicate
$M_textrm{gas}sim2times10^{11}$M$_odot$, and suggest a modestly larger
$alpha_{textrm{CO}}$ value of $sim$8.2. The corresponding gas depletion
timescale is $sim$1.5 Gyr. In addition to gas of modest density (Log($n$
cm$^3)lesssim3$ ) heated by star formation, BX610 shows evidence for a
significant second gas component responsible for the strong high-J CO emission.
This second component might either be a high-density molecular gas component
heated by star formation in a typical photodissociation region, or could be
molecular gas excited by low-velocity C shocks. The CO(7-6)-to-FIR luminosity
ratio we observe is significantly higher than typical star-forming galaxies and
suggests that CO(7-6) is not a reliable star-formation tracer in this galaxy.

We used the Plateau De Bure Interferometer to observe multiple CO and neutral
carbon transitions in a z=2.2 main sequence disk galaxy, BX610. Our observation
of CO(7-6), CO(4-3), and both far-infrared(FIR) [CI] lines complements previous
observations of H$alpha$ and low-J CO, and reveals a galaxy that is vigorously
forming stars with UV fields (Log($G$ G$_0^{-1}) lesssim3.25);$ although less
vigorously than local ultra-luminous infrared galaxies or most starbursting
submillimeter galaxies in the early universe. Our observations allow new
independent estimates of the cold gas mass which indicate
$M_textrm{gas}sim2times10^{11}$M$_odot$, and suggest a modestly larger
$alpha_{textrm{CO}}$ value of $sim$8.2. The corresponding gas depletion
timescale is $sim$1.5 Gyr. In addition to gas of modest density (Log($n$
cm$^3)lesssim3$ ) heated by star formation, BX610 shows evidence for a
significant second gas component responsible for the strong high-J CO emission.
This second component might either be a high-density molecular gas component
heated by star formation in a typical photodissociation region, or could be
molecular gas excited by low-velocity C shocks. The CO(7-6)-to-FIR luminosity
ratio we observe is significantly higher than typical star-forming galaxies and
suggests that CO(7-6) is not a reliable star-formation tracer in this galaxy.

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