Zooming on the internal structure of z≃6 galaxies

We present zoom-in, AMR, high-resolution ($simeq 30$ pc) simulations of high-redshift ($z simeq 6$) galaxies with the aim of characterizing their internal properties and interstellar medium. Among other features, we adopt a star formation model based on a physically-sound molecular hydrogen prescription, and introduce a novel scheme for supernova feedback, stellar winds and dust-mediated radiation pressure. In the zoom-in simulation the target halo hosts "Dahlia", a galaxy with a stellar mass $M_*=1.6 imes 10^10$M$_odot$, representative of a typical $zsim 6$ Lyman Break Galaxy. Dahlia has a total H2 mass of $10^8.5$M$_odot$, that is mainly concentrated in a disk-like structure of effective radius $simeq 0.6$ kpc and scale height $simeq 200$ pc. Frequent mergers drive fresh gas towards the center of the disk, sustaining a star formation rate per unit area of $simeq 15 $M$_odot$ yr$^-1$ kpc$^-2$. The disk is composed by dense ($n gtrsim 25$ cm$^-3$), metal-rich ($Z simeq 0.5 $ Z$_odot$) gas, that is pressure-supported by radiation. We compute the $158mu$m [CII] emission arising from Dahlia, and find that $simeq 95%$ of the total [CII] luminosity ($L_[CII]simeq10^7.5$ L$_odot$) arises from the H2 disk. Although $30%$ of the CII mass is transported out of the disk by outflows, such gas negligibly contributes to [CII] emission, due to its low density ($n lesssim 10$ cm$^-3$) and metallicity ($Zlesssim 10^-1$Z$_odot$). Dahlia is under-luminous with respect to the local [CII]-SFR relation; however, its luminosity is consistent with upper limits derived for most $zsim6$ galaxies.

We present zoom-in, adaptive mesh refinement, high-resolution (≃30 pc) simulations of high-redshift (z ≃ 6) galaxies with the aim of characterizing their internal properties and interstellar medium. Among other features, we adopt a star formation model based on a physically sound molecular hydrogen prescription, and introduce a novel scheme for supernova feedback, stellar winds and dust-mediated radiation pressure. In the zoom-in simulation, the target halo hosts ‘Dahlia’, a galaxy with a stellar mass M⋆ = 1.6 × 1010 M⊙, representative of a typical z ∼ 6 Lyman-break galaxy. Dahlia has a total H2 mass of 108.5 M⊙ that is mainly concentrated in a disc-like structure of effective radius ≃0.6 kpc and scale height ≃200 pc. Frequent mergers drive fresh gas towards the centre of the disc, sustaining a star formation rate per unit area of ≃15 M⊙ yr−1 kpc−2. The disc is composed of dense (n ≳ 25 cm−3), metal-rich (Z ≃ 0.5 Z⊙) gas that is pressure supported by radiation. We compute the 158 μm [C ii] emission arising from Dahlia, and find that ≃95 per cent of the total [C ii] luminosity (⁠L[CII]≃107.5L⊙⁠) arises from the H2 disc. Although 30 per cent of the C ii mass is transported out of the disc by outflows, such gas negligibly contributes to [C ii] emission, due to its low density (n ≲ 10 cm−3) and metallicity (Z ≲ 10−1 Z⊙). Dahlia is underluminous with respect to the local [C ii]–SFR relation; however, its luminosity is consistent with upper limits derived for most z ∼ 6 galaxies.