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Accueil > Séminaires > Archive des séminaires d’Utinam > 2013

Mathieu Servillat

Tracing the build-up of galaxies through their compact object populations

mardi 8 octobre 2013, 14h

salle de conférences de l’observatoire

Mathieu Servillat ), CEA Saclay / Harvard-Smithsonian CfA

Résumé :

The study of populations of compact objects (black holes, neutron stars and white dwarfs) can help us to better understand how the Galaxy and its central black hole formed.

I will first focus on the Galactic Center region, where a large number of X-ray sources has been detected : about 2500 in a field of view of 10’x10’ (25 pc at the Galactic Center distance). The identification of those sources, which seem to be various accreting compact objects in binary systems, would bring new elements in the understanding of the history of the Galactic bulge. However, severe crowding and extreme interstellar extinction prevent us to associate the X-ray sources with their optical/infrared counterparts. Using multiple epoch infrared imaging over 7 years and multi-object spectroscopy, I present new advances in the identification of those X-ray sources.

In a second part, I will focus on the study of the ultra-luminous X-ray source ESO 243-49 HLX-1. I will first bring strong evidence that this source is the best intermediate mass black hole candidate currently known (around 10^4 Msun). I will then discuss the spectral energy distribution obtained with Hubble and Swift XRT which indicates the presence of 10^7-10^8 yr stellar population surrounding the black hole, suggesting that a minor merger is in progress. Disturbance in the globular cluster system of the host galaxy ESO 243-49 also suggests the presence of other minor mergers. This unique glance at live minor mergers favors a hierarchical scenario where supermassive black holes, and their host galaxies, regularly grow through the accretion of smaller black holes in smaller galaxies.