Essential physics of early galaxy formation

Pratika Dayal; Andrea Ferrara; James Dunlop; Fabio Pacucci

doi:10.1093/mnras/stu1848

paper

Essential physics of early galaxy formation

arXiv:1405.4862 · doi:10.1093/mnras/stu1848

Abstract

We present a theoretical model embedding the essential physics of early galaxy formation (z = 5-12) based on the single premise that any galaxy can form stars with a maximal limiting efficiency that provides enough energy to expel all the remaining gas, quenching further star formation. This simple idea is implemented into a merger-tree based semi-analytical model that utilises two mass and redshift-independent parameters to capture the key physics of supernova feedback in ejecting gas from low-mass halos, and tracks the resulting impact on the subsequent growth of more massive systems via halo mergers and gas accretion. Our model shows that: (i) the smallest halos (halo mass $M_{h} \leq 1 0^{10} M_{⊙}$ ) build up their gas mass by accretion from the intergalactic medium; (ii) the bulk of the gas powering star formation in larger halos ( $M_{h} \geq 1 0^{11.5} M_{⊙}$ ) is brought in by merging progenitors; (iii) the faint-end UV luminosity function slope evolves according to $α = - 1.75 lo g z - 0.52$ . In addition, (iv) the stellar mass-to-light ratio is well fit by the functional form $lo g M_{*} = - 0.38 M_{U V} - 0.13 z + 2.4$ , which we use to build the evolving stellar mass function to compare to observations. We end with a census of the cosmic stellar mass density (SMD) across galaxies with UV magnitudes over the range $- 23 \leq M_{U V} \leq - 11$ spanning redshifts $5 < z < 12$ : (v) while currently detected LBGs contain $\approx 50$ % (10%) of the total SMD at $z = 5$ (8), the JWST will detect up to 25% of the SMD at $z ≃ 9.5$ .

arXiv commentAccepted to MNRAS with minor changes

Essential physics of early galaxy formation

Abstract

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