European Astronomical Society
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|PhD Fellowship in Binary black hole mergers from globular clusters||Closing date: 2023-01-25
Contact: La Caixa Fellowships
|In this PhD project you will model the evolution of globular cluster (GC) populations in different galaxy types, with a particular focus on the Milky Way. You will make predictions for the present-day structure and kinematics of GCs, their distribution in the galaxy, and the distribution of the escaped stars in the galaxy. You will compare these to observations of GCs and field stars that escaped from surviving and dissolved GCs. All of these observables are sensitive to the details of the black hole (BH) populations in the GCs, so astronomical observations can be used to constrain BH dynamics|
Gravitational waves (GWs) provide a new window on our Universe. The vast majority of the GW detections by the LIGO-Virgo interferometers are from binary black holes (BBHs). The origin of these BBHs is an open question: they may have a cosmological origin and be part of the dark matter in the Universe. Alternatively, they have an astrophysical origin and formed from binary massive stars, or in dynamical interactions in dense stellar systems such as globular clusters (GCs).
This project aims to understand the contribution of dynamically formed BBH mergers. Understanding this is of vital importance to understand the nature of BBHs, but it is challenging because the BBH properties and merger rate in this dynamical channel depend sensitively on the unknown initial properties of GCs that formed between now and more than 10 Gyr ago. You will constrain the contribution of the dynamical channel by comparing population models of GC evolution and BBH mergers to observations of Milky Way GCs and use the fact that BHs in GCs affect their observable properties and the stellar escape rate from GCs. You will exploit data from the Gaia space telescope and related surveys such as WEAVE to chart the demographics of BHs in both dissolved and surviving GCs.
The ICCUB is a full member of the Virgo collaboration and actively involved in Gaia (PI Carme Jordi) and the WEAVE survey, giving you access new data and analysis allowing you to work on the forefront of GW sand Milky Way research. You will join the enthusiastic Virgo and Gaia research groups of the ICCUB who organize weekly science meetings, journal clubs and seminars. You will also benefit from scientific collaborations with various ICCUB staff in the areas of star formation (Paolo Padoan), galaxy formation (Chervin Laporte, Teresa Antoja), cosmology (Licia Verde, Jordi Miralda) and black holes (Cristiano Germani, Jaume Garriga). Finally, you will be part of international collaborations with groups in Europe, Canada and the US.
Job position description
In this PhD project you will model the evolution of globular cluster (GC) populations in different galaxy types, with a particular focus on the Milky Way. You will make predictions for the present-day structure and kinematics of GCs, their distribution in the galaxy, and the distribution of the escaped stars in the galaxy. You will compare these to observations of GCs and field stars that escaped from surviving and dissolved GCs. All of these observables are sensitive to the details of the black hole (BH) populations in the GCs, so astronomical observations can be used to constrain BH dynamics.
The research group at ICCUB - led by Prof Mark Gieles - developed an ultra-fast code for simulating the evolution of GCs and their BH populations, enabling the exploration of the parameter space of initial properties of GCs. This will be used to model GC populations and chart the demographics BHs in GCs, now and in the past.
These population models are then combined with fast models for the evolution of the BBHs within the GCs to forward model the rate and properties of BBH mergers. The results will provide insights in both the evolutionary history of each GC and its BH population as well as the resulting BBH merger rates, constrained by observational data. The results for the Milky Way GC population are then extrapolated to compute the BBH merger rate of all GCs in the Universe across cosmic time. The predictions include merger rate as a function of redshift, BH masses, mass ratios and the distribution of orbital eccentricities. These will be compared to gravitational wave (GW) data of BBH mergers in the ongoing LIGO-Virgo observing runs, to provide tight constraints on the fraction of all BBH mergers that originate from the dynamical channel. This project also sheds light on the parameters describing the initial conditions of GCs, thereby opening to door to use GWs to constrain star and cluster formation in the early Universe.
Prof. Mark Gieles ?mgieles @ icc.ub.edu
Research product / Research group
ICCUB participation in Virgo
ICCUB participation in Gaia
paper presenting a model for binary black hole mergers from globular clusters and a comparison to the latest catalogue of gravitational wave sources.
recent paper on the inference of a large black hole population in a Galactic globular cluster from its tidal tails
recent paper demonstrating how the mass of a black hole population can be inferred from observations of the globular cluster 47 Tuc.
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