The formation of high-redshift submillimetre galaxies

Abstract

We describe a model for the formation of z∼ 2 submillimetre galaxies (SMGs) which simultaneously accounts for both average and bright SMGs while providing a reasonable match to their mean observed spectral energy distributions (SEDs). By coupling hydrodynamic simulations of galaxy mergers with the high-resolution 3D polychromatic radiative transfer code sunrise, we find that a mass sequence of merger models which use observational constraints as physical input naturally yield objects which exhibit black hole, bulge and H2 gas masses similar to those observed in SMGs. The dominant drivers behind the 850 μm flux are the masses of the merging galaxies and the stellar birth cloud covering fraction. The most luminous (S850≳ 15 mJy) sources are recovered by ∼1013 M⊙ 1:1 major mergers with a birth cloud covering fraction close to unity, whereas more average SMGs (S850∼ 5–7 mJy) may be formed in lower mass haloes (∼5 × 1012 M⊙). These models demonstrate the need for high spatial resolution hydrodynamic and radiative transfer simulations in matching both the most luminous sources as well as the full SEDs of SMGs. While these models suggest a natural formation mechanism for SMGs, they do not attempt to match cosmological statistics of galaxy populations; future efforts along this line will help ascertain the robustness of these models.