The z~6 Luminosity Function Fainter than -15 mag from the Hubble Frontier Fields: The Impact of Magnification Uncertainties

Understand

We use the largest sample of z~6 galaxies to date from the first four Hubble Frontier Fields clusters to set constraints on the shape of the z~6 luminosity functions (LFs) to fainter than Muv=-14 mag.

• We quantify, for the first time, the impact of magnification uncertainties on LF results and thus provide more realistic constraints than other recent work.
• Our simulations reveal that for the highly-magnified sources the systematic uncertainties can become extremely large fainter than -14 mag, reaching several orders of magnitude at 95% confidence at ~-12 mag.
• Our new forward-modeling formalism incorporates the impact of magnification uncertainties into the LF results by exploiting the availability of many independent magnification models for the same cluster.