Project D

The most extreme environment of the Galaxy. Unveiling the metallicity of a young stellar cluster in the Galactic centre

Francisco Nogueras Lara

(email advisor)

The Galactic centre is an extreme stellar environment characterised by high stellar crowding, extreme extinction, intense radiation, and high turbulence and temperature of the interstellar medium. In spite of these harsh conditions, it is the most prolific star-forming environment of the Galaxy when averaged over volume, being responsible for up to 10% of the total Milky Way’s star formation activity in the last 100 Myr. Hence, it provides an ideal setting for exploring star formation in challenging conditions akin to those found in starburst or high-redshift galaxies.  

At the heart of this unique environment lies Quintuplet, a young stellar cluster with an estimated age of ~3-4 Myr. Although a photometric analysis of its stars has been possible, the characterisation of its metallicity is very challenging. Given its youth, it is dominated by hot stars whose spectral analysis is hampered by the absence of spectral lines to measure their chemical composition. Understanding the metallicity of young stars in the Galactic centre is key to unveiling the formation of its stellar structures and its relation to other Galaxy components such as the Galactic bar or the disc.  

To shed light on this problem, this project aims to unravel the metallicity of Quintuplet by using HST photometric data and comparing the stellar distribution in a colour-magnitude diagram with synthetic models accounting for different metallicities. The expected tasks of this project include: i) Using HST proper motions to create a clean sample of Quintuplet stars by removing field stars and stars along the line of sight. ii) Building an extinction map to correct the reddening of Quintuplet stars. iii) Comparing the de-reddened photometry with theoretical models to statistically determine the metallicity of Quintuplet.

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