Establishing an analogue population for the most distant galaxies
Lyman break analogues (LBAs) are local galaxies selected to match a more distant (usually z ∼ 3) galaxy population in luminosity, UV-spectral slope and physical characteristics, and so provide an accessible laboratory for exploring their properties. However, as the Lyman break technique is extended to higher redshifts, it has become clear that the Lyman break galaxies (LBGs) at z ∼ 3 are more massive, luminous, redder, more extended and at higher metallicities than their z ∼ 5 counterparts. Thus extrapolations from the existing LBA samples (which match z = 3 properties) have limited value for characterizing z > 5 galaxies, or inferring properties unobservable at high redshift. We present a new pilot sample of 21 compact star-forming galaxies in the local (0.05 < z < 0.25) Universe, which are tuned to match the luminosities and star formation volume densities observed in z ≳ 5 LBGs. The analysis of optical emission line indices suggests that these sources have typical metallicities of a few tenths solar (again, consistent with the distant population). We also present radio continuum observations of a subset of this sample (13 sources) and determine that their radio fluxes are consistent with those inferred from the ultraviolet, precluding the presence of a heavily obscured active galactic nuclei or significant dusty star formation.