MORGOTH: incorporating horizontal branch modelling into star formation history determinations

TL;DR

MORGOTH is a new method that improves star formation history determinations by incorporating horizontal branch morphology, leading to more precise results and better modeling of stellar evolution phases.

Contribution

It introduces a novel approach that self-consistently includes horizontal branch modeling into star formation history analysis, enhancing accuracy and resolving degeneracies.

Findings

Increased precision in star formation histories with horizontal branch inclusion

Successful application to Sculptor dwarf galaxy, revealing detailed history

Good agreement with previous analyses, validating the method

Abstract

We present a new method that incorporates the horizontal branch morphology into synthetic colour-magnitude diagram based star formation history determinations. This method, we call MORGOTH, self-consistently takes into account all the stellar evolution phases up to the early asymptothic giant branch, flexibly modelling red giant branch mass loss. We test MORGOTH on a range of synthetic populations, and find that the inclusion of the horizontal branch significantly increases the precision of the resulting star formation histories. When the main sequence turn-off is detected, MORGOTH can fit the star formation history and the red giant branch mass loss at the same time, efficiently breaking this degeneracy. As part of testing MORGOTH, we also model the observed colour-magnitude diagram of the well studied Sculptor dwarf spheroidal galaxy. We recover a new more detailed star formation history for this galaxy. Both the new star formation history and the red giant branch mass loss we determined for Sculptor with MORGOTH are in good agreement with previous analyses, thus demonstrating the power of this new approach.