The stellar populations of high-redshift dwarf galaxies

Abstract

ABSTRACT We use high-resolution (≈10 pc), zoom-in simulations of a typical (stellar mass $M_\star \simeq 10^{10}\, {\rm M}_{\odot }$) Lyman Break Galaxy (LBG) at z ≃ 6 to investigate the stellar populations of its six dwarf galaxy satellites, whose stellar [gas] masses are in the range log (M⋆/M⊙) ≃ 6−9 [log (Mgas/M⊙) ≃ 4.3−7.75]. The properties and evolution of satellites show no dependence on the distance from the central massive LBG (<11.5 kpc). Instead, their star formation and chemical enrichment histories are tightly connected to their stellar (and sub-halo) mass. High-mass dwarf galaxies ($M_\star \gtrsim 5\times 10^8 \, {\rm M}_{\odot }$) experience a long history of star formation, characterized by many merger events. Lower mass systems go through a series of short star formation episodes, with no signs of mergers; their star formation activity starts relatively late (z ≈ 7), and it is rapidly quenched by internal stellar feedback. In spite of the different evolutionary patterns, all satellites show a spherical morphology, with ancient and more metal-poor stars located towards the inner regions. All six dwarf satellites experienced high star formation rate ($\rm \gt 5\, {\rm M}_{\odot }\, {\rm yr}^{-1}$) bursts, which can be detected by James Webb Space Telescope while targeting high-z LBGs.