The stellar populations of high-redshift dwarf galaxies

Abstract

We use high-resolution ($\approx 10$ pc), zoom-in simulations of a typical (stellar mass $M_{\star }\simeq 10^{10}{M}_{\odot }$) Lyman Break Galaxy (LBG) at $z\simeq 6$ to investigate the stellar populations of its six dwarf galaxy satellites, whose stellar [gas] masses are in the range $\log (M_{\star }/M_{\odot })\simeq 6-9$ [$\log (M_{gas}/M_{\odot })\simeq 4.3-7.75$]. 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 their stellar (and sub-halo) mass. High-mass dwarf galaxies (${\mathrm{M}}_{\star }\gtrsim 5\times 10^8{\mathrm{M}}_{\odot }$) experience a long history of star formation, characterised 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 ($z\approx 7$), 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 ($>5{\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$) bursts, which can be detected by JWST while targeting high-$z$ LBGs.

17 pages, 14 figures. To be published in MNRAS

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• The energy distribution of the first supernovae
• On the dearth of C-enhanced metal-poor stars in the Galactic bulge