Spectroscopic Confirmation of the Dragonfish Association: The Galaxy's Most Luminosity OB Association

TL;DR

This study spectroscopically confirms the existence of the Dragonfish OB association, the most luminous and massive OB association in the Galaxy, validating the detection method and revealing a powerful stellar group within the Dragonfish Nebula.

Contribution

First spectroscopic confirmation of the Dragonfish OB association, establishing it as the Galaxy's most luminous OB association and validating the color selection detection method.

Findings

Confirmed 18 massive stars in the association

Association's mass exceeds 10^5 solar masses

Validates the color selection detection method

Abstract

Young OB associations with masses greater than 10$^4$ M$_{\sun}$ have been inferred to exist in the Galaxy but have largely evaded detection. Recently, a candidate OB association has been identified within the most luminous star forming complex in the Galaxy, the Dragonfish Nebula. We identify 18 young, massive stars with near-infrared spectroscopy from a sample of 50 members within the candidate OB association, including 15 O-type, and three Luminous Blue Variables or Wolf-Rayet stars. This number matches the expected yield of massive stars from the candidate association, confirming its existence and ability to power the parent star forming complex. These results demonstrate the existence of a 10$^5$ M$_{\sun}$ OB association, more powerful than any previously known in the Galaxy, comparable in mass only to Westerlund 1. Further, the results also validate the color selection method used to identify the association, adding credence to others discovered in the same way.