Metals and ionizing photons from dwarf galaxies

S. Salvadori, E. Tolstoy, A. Ferrara, S. Zaroubi

Research output: Contribution to journalArticlepeer-review


We estimate the potential contribution of M < 109Modot dwarf galaxies to the reionization and early metal enrichment of the Milky Way environment, or circum-Galactic medium. Our approach is to use the observed properties of ancient stars (odot12 Gyr old) measured in nearby dwarf galaxies to characterize the star formation at high z.We use a merger-tree model for the build-up of the Milky Way, which self-consistently accounts for feedback processes, and which is calibrated to match the present-day properties of the Galaxy and its dwarf satellites.We show that the high-z analogues of nearby dwarf galaxies can produce the bulk of ionizing radiation (>80 per cent) required to reionize theMilkyWay environment. Our fiducial model shows that the gaseous environment can be 50 per cent reionized at z ̃ 8 by galaxies with 107Modot = M < 108Modot. At later times, radiative feedback stops the star formation in these small systems, and reionization is completed by more massive dwarf galaxies by zrei = 6.4 ± 0.5. The metals ejected by supernova-driven outflows from M < 109Modot dwarf galaxies almost uniformly fill the Milky Way environment by z ̃ 5, enriching it to Z ̃ 2 × 10-2 Zodot. At z ̃ 2, these early metals are still found to represent the ̃50 per cent of the total mass of heavy elements in the circum-Galactic medium

Original languageEnglish
Article numberslt132
Pages (from-to)L26-L30
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
StatePublished - 1 Jan 2014
Externally publishedYes


  • Dwarf-galaxies
  • Galaxies
  • High-redshift-local group-cosmology
  • Theory


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