In savvy pursuit of Local Group blue massive stars

TL;DR

This paper introduces a new method using a friends of friends algorithm and photometric criteria to identify and analyze OB associations and massive stars in Local Group galaxies, enhancing the study of their evolution and distribution.

Contribution

The authors developed an automated method to identify OB associations and estimate stellar masses, improving candidate selection for spectroscopy in Local Group galaxies.

Findings

Effective identification of OB associations in IC 1613.

Revealed galaxy structure and recent star formation history.

Enabled better candidate selection for spectroscopic follow-up.

Abstract

The important role of metallicity on massive star evolution and the combination of multi-object spectrographs and 10m class telescopes, have lead to numerous systematic studies of massive stars in Local Group galaxies. While color based quests of blue massive stars are relatively successful, they must be confirmed with spectroscopy and usually lead to lists dominated by B-type modest-mass stars. We have developed a friends of friends code to find OB associations in Local Group galaxies, presented in Garcia et al. (2009). One of the key points of the method is the photometric criterion to choose candidate OB stars from the reddening-free Q parameter, that could be easily extended to include from GALEX to near-IR photometry. While not a new idea, one of our code's strong advantages is the automatic determination of evolutionary masses for the members, enabling a quick and more insightful choice of candidates for spectroscopy, and the identification of potential advanced evolutionary stages. We present our work on the very metal-poor irregular IC 1613 (Garcia et al. 2010). The association properties are not only a powerful aid towards finding the most interesting candidate massive stars, but also reveal the galaxy's structure and recent star formation history.