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Maximum-likelihood implementation of the tip-of-the-red-giant-branch method

Published online by Cambridge University Press:  26 February 2013

Dmitry Makarov*
Affiliation:
Special Astrophysical Observatory, Russian Academy of Sciences, N. Arkhyz, KChR, 369167, Russia email: [email protected]
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Abstract

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The luminosity of the tip of the red giant branch (TRGB) provides an excellent measure of galaxy distances and is easily determined in the resolved images of nearby galaxies observed with the Hubble Space Telescope (HST). We use a maximum-likelihood algorithm to locate the TRGB in galaxy colour–magnitude diagrams. The algorithm is optimized by introducing reliable photometric errors and a completeness characterization determined based on artificial-star experiments. The program has been tested extensively using Monte Carlo simulations, artificial galaxies, and a sample of nearby dwarf galaxies observed with the HST's WFPC2 and ACS cameras. Our procedure is shown to be reliable, yield good accuracy, and does not introduce any systematic errors. The methodology is especially useful in cases in which the TRGB approaches the photometric limit and/or the RGB is poorly populated.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2013

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