New windows onto the stellar population at the Galactic CentreMulti–wavelength and time-domain studies

Resumo

The objective of this thesis is the study of the massive stars belonging to two of the most emblematic clusters of the Galactic centre, the Arches and Quintuplet clusters, both located about 30 parsecs in projection of Sagittarius A*, the central black hole of the Milky Way, using very high angular resolution radio interferometric techniques. These techniques allow us to observe distant objects separated by a very small angular distance, synthesising an aperture equivalent to the distance between pairs of antennas, an aperture that would not be possible to achieve with a single dish radio telescope. Due to the very high extinction in this region, the observational studies of these two clusters have been mainly limited to observations in the near infrared, with spectroscopy and photometry, as the optical range is practically inaccesible and the mid-infrared is limited due to the angular resolution and/or the sensitivity of the instruments in an enclave heavily populated with stars. Given the low statistics of radio observations of the ionised winds of massive stars and the existence of them in the Arches and Quintuplet clusters, this work is a new step towards understanding this type of stars and the clusters that contain them. All the studies presented here have been carried out using the Karl G. Janksy Very Large Array (JVLA) radio interferometer operated by the National Radio Astronomy Observatory (NRAO)2. In this work, we have obtained: a) a new census, in both clusters, of the number of massive stars observed in centimetre radio wavelengths, b) their fluxes and positions, c) estimated mass-loss rates, d) an assessment of their possible multiplicity based on the calculated spectral index, e) an assessment of variability, and finally, f) an estimate, within certain limits, of the age and/or mass of the clusters, as well as the IMF based, precisely, on the number of radio sources detected. This thesis is composed of six chapters. In the first one, a brief introduction is given about the science that is in it. In the second chapter, the principles of radio interferometry are exposed, emphasising the fundamental aspects that have given rise to this work. In chapters three and four, the main research topics of this thesis are presented. These include the data, analysis, and results described in a peerreviewed publication and in one to be submitted imminently. Finally, chapters five and six present the general conclusions and future lines of research of this thesis.