Quantifying Uncertainties on the Tip of the Red Giant Branch Method

Understand

We present an extensive grid of numerical simulations quantifying the uncertainties in measurements of the Tip of the Red Giant Branch (TRGB).

• These simulations incorporate a luminosity function composed of 2 magnitudes of red giant branch (RGB) stars leading up to the tip, with asymptotic giant branch (AGB) stars contributing exclusively to the luminosity function for at least a magnitude above the RGB tip.
• We quantify the sensitivity of the TRGB detection and measurement to three important error sources: (1) the sample size of stars near the tip, (2) the photometric measurement uncertainties at the tip, and (3) the degree of self-crowding of the RGB population.
• The self-crowding creates a population of supra-TRGB stars due to the blending of one or more RGB stars just below the tip.