Dwarf Satellites of High-z Lyman Break Galaxies: A Free Lunch for JWST

We show that the James Webb Space Telescope (JWST) will be able to detect dwarf satellites of high-z Lyman break galaxies (LBGs). To this end, we use cosmological simulations following the evolution of a typical M-*similar or equal to 10(10) M-circle dot LBG up to z similar or equal to 6, and analyze the observational properties of its five satellite dwarf galaxies (10(7) M-circle dot < M-* < 10(9) M-circle dot). Modeling their stellar emission and dust attenuation, we reconstruct their rest-frame ultraviolet-optical spectra for 6 < z < 6.5. JWST/NIRCam synthetic images show that the satellites can be spatially resolved from their host, and their emission is detectable by planned deep surveys. Moreover, we build synthetic spectral energy distributions and color-magnitude diagrams for the satellites. We conclude that the color F200W-F356W is a powerful diagnostic tool for understanding their physical properties once they have been identified. For example, F200W-F356W less than or similar to -0.25 can be used to identify star-bursting (SFR similar to 5 M-circle dot yr(-1)), low-mass (M-* less than or similar to 5 x 10(8) M-circle dot) systems, with similar to 80% of their stars being young and metal poor [log(Z(*)/Z(circle dot)) < -0.5].