Dust temperature in ALMA $hbox{[C $scriptstylerm II $]}$-detected high-$z$ galaxies. (arXiv:2102.08950v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Sommovigo_L/0/1/0/all/0/1">L. Sommovigo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ferrara_A/0/1/0/all/0/1">A. Ferrara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carniani_S/0/1/0/all/0/1">S. Carniani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zanella_A/0/1/0/all/0/1">A. Zanella</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pallottini_A/0/1/0/all/0/1">A. Pallottini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gallerani_S/0/1/0/all/0/1">S. Gallerani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vallini_L/0/1/0/all/0/1">L. Vallini</a>
At redshift $z>5$ the far-infrared (FIR) continuum spectra of main-sequence
galaxies are sparsely sampled, often with a single data point. The dust
temperature $T_{rm d, SED}$ thus has to be assumed in the FIR continuum
fitting. This introduces large uncertainties regarding the derived dust mass
($M_{rm d}$), FIR luminosity, and obscured fraction of the star formation
rate. These are crucial quantities to quantify the effect of dust obscuration
in high-$z$ galaxies. To overcome observations limitations, we introduce a new
method that combines dust continuum information with the overlying $hbox{[C
$scriptstylerm II $]} 158mu$m line emission. By breaking the $M_{rm d} –
T_{rm d, SED}$ degeneracy, with our method, we can reliably constrain the dust
temperature with a single observation at $158mu$m. This method can be applied
to all ALMA and NOEMA $hbox{[C $scriptstylerm II $]}$ observations and
exploited in ALMA Large Programs such as ALPINE and REBELS targeting $hbox{[C
$scriptstylerm II $]}$ emitters at high-$z$. We also provide a physical
interpretation of the empirical relation recently found between $molecular$ gas
mass and $hbox{[C $scriptstylerm II $]}$ luminosity. We derive an analogous
relation linking the $total$ gas surface density and $hbox{[C $scriptstylerm
II $]}$ surface brightness. By combining the two, we predict the cosmic
evolution of the surface density ratio $Sigma_{rm H_2} / Sigma_{rm gas}$.
We find that $Sigma_{rm H_2} / Sigma_{rm gas}$ slowly increases with
redshift, which is compatible with current observations at $0 < z < 4$.
At redshift $z>5$ the far-infrared (FIR) continuum spectra of main-sequence
galaxies are sparsely sampled, often with a single data point. The dust
temperature $T_{rm d, SED}$ thus has to be assumed in the FIR continuum
fitting. This introduces large uncertainties regarding the derived dust mass
($M_{rm d}$), FIR luminosity, and obscured fraction of the star formation
rate. These are crucial quantities to quantify the effect of dust obscuration
in high-$z$ galaxies. To overcome observations limitations, we introduce a new
method that combines dust continuum information with the overlying $hbox{[C
$scriptstylerm II $]} 158mu$m line emission. By breaking the $M_{rm d} –
T_{rm d, SED}$ degeneracy, with our method, we can reliably constrain the dust
temperature with a single observation at $158mu$m. This method can be applied
to all ALMA and NOEMA $hbox{[C $scriptstylerm II $]}$ observations and
exploited in ALMA Large Programs such as ALPINE and REBELS targeting $hbox{[C
$scriptstylerm II $]}$ emitters at high-$z$. We also provide a physical
interpretation of the empirical relation recently found between $molecular$ gas
mass and $hbox{[C $scriptstylerm II $]}$ luminosity. We derive an analogous
relation linking the $total$ gas surface density and $hbox{[C $scriptstylerm
II $]}$ surface brightness. By combining the two, we predict the cosmic
evolution of the surface density ratio $Sigma_{rm H_2} / Sigma_{rm gas}$.
We find that $Sigma_{rm H_2} / Sigma_{rm gas}$ slowly increases with
redshift, which is compatible with current observations at $0 < z < 4$.
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