Reproducing sub-millimetre galaxy number counts with cosmological hydrodynamic simulations. (arXiv:2006.15156v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Lovell_C/0/1/0/all/0/1">Christopher C. Lovell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Geach_J/0/1/0/all/0/1">James E. Geach</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dave_R/0/1/0/all/0/1">Romeel Davé</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Narayanan_D/0/1/0/all/0/1">Desika Narayanan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_Q/0/1/0/all/0/1">Qi Li</a>
Matching the number counts of high-$z$ sub-millimetre-selected galaxies
(SMGs) has been a long standing problem for galaxy formation models. In this
paper, we use 3D dust radiative transfer to model the sub-mm emission from
galaxies in the SIMBA cosmological hydrodynamic simulations, and compare
predictions to the latest single-dish observational constraints on the
abundance of 850$mathrm{mu m}$-selected sources. We find unprecedented
agreement with the integrated 850$mathrm{mu m}$ luminosity function, along
with good agreement in the redshift distribution of bright SMGs. The excellent
agreement is driven primarily by SIMBA’s good match to infrared measures of the
star formation rate (SFR) function between $z = 2-4$ at high SFRs. Also
important is the self-consistent on-the-fly dust model in SIMBA, which
predicts, on average, higher dust masses (by up to a factor of 7) compared to
using a fixed dust-to-metals ratio of 0.3. We construct a lightcone to
investigate the effect of far-field blending, and find minimal contribution to
the shape and normalisation of the luminosity function. We provide new fits to
the 850$mathrm{mu m}$ luminosity as a function of SFR and dust mass. Our
results demonstrate that exotic solutions to the discrepancy between sub-mm
counts in simulations and observations, such as a top-heavy IMF, are
unnecessary, and that sub-millimetre-bright phases are a natural consequence of
massive galaxy evolution.
Matching the number counts of high-$z$ sub-millimetre-selected galaxies
(SMGs) has been a long standing problem for galaxy formation models. In this
paper, we use 3D dust radiative transfer to model the sub-mm emission from
galaxies in the SIMBA cosmological hydrodynamic simulations, and compare
predictions to the latest single-dish observational constraints on the
abundance of 850$mathrm{mu m}$-selected sources. We find unprecedented
agreement with the integrated 850$mathrm{mu m}$ luminosity function, along
with good agreement in the redshift distribution of bright SMGs. The excellent
agreement is driven primarily by SIMBA’s good match to infrared measures of the
star formation rate (SFR) function between $z = 2-4$ at high SFRs. Also
important is the self-consistent on-the-fly dust model in SIMBA, which
predicts, on average, higher dust masses (by up to a factor of 7) compared to
using a fixed dust-to-metals ratio of 0.3. We construct a lightcone to
investigate the effect of far-field blending, and find minimal contribution to
the shape and normalisation of the luminosity function. We provide new fits to
the 850$mathrm{mu m}$ luminosity as a function of SFR and dust mass. Our
results demonstrate that exotic solutions to the discrepancy between sub-mm
counts in simulations and observations, such as a top-heavy IMF, are
unnecessary, and that sub-millimetre-bright phases are a natural consequence of
massive galaxy evolution.
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