Periodic Reporting for period 4 - ArcheoDyn (Globular clusters as living fossils of the past of galaxies)
Período documentado: 2022-03-01 hasta 2023-02-28
Globular clusters (GCs) are the living fossils of the history of their native galaxies and the record keepers of the violent events that made them change their domicile. This project aims to mine GCs as living fossils of galaxy evolution to address fundamental questions in astrophysics:
1: What are the seeds of supermassive black holes in the centers of galaxies? ⟷ Do GCs harbor such seeds in the form of intermediate mass black holes?
2: How did star formation originate in the earliest phases of galaxy formation? ⟷ Can we uncover the origin of multiple stellar populations in ancient GCs and so shed light on star formation in the early Universe?
3: Do satellite galaxies merge as predicted by the hierarchical build-up of galaxies? ⟷ Can we recover disrupted satellite galaxies from the GCs they left in their host?
To answer these questions we develop and apply population-dependent dynamical models to take full advantage of the emerging wealth of chemical and kinematical data on GCs.
The algorithms developed and applied to answer the above science questions are also applicable beyond astrophysics to various technological challenges presented by e.g. Big Data and super-resolution imaging in medicine, biology, and engineering. Team members will receive training through research in the top five skills needed in the 2020s landscape: complex problem solving, critical thinking, creativity, people management, and coordinating with others. The outcomes of this project and astrophysics in general can spark the interest of the public and serve as a gateway, particularly in young people, to scientific concepts in STEM.
1: What are the seeds of supermassive black holes in the centers of galaxies? ⟷ Do GCs harbor such seeds in the form of intermediate mass black holes?
2: How did star formation originate in the earliest phases of galaxy formation? ⟷ Can we uncover the origin of multiple stellar populations in ancient GCs and so shed light on star formation in the early Universe?
3: Do satellite galaxies merge as predicted by the hierarchical build-up of galaxies? ⟷ Can we recover disrupted satellite galaxies from the GCs they left in their host?
To answer these questions we develop and apply population-dependent dynamical models to take full advantage of the emerging wealth of chemical and kinematical data on GCs.
The algorithms developed and applied to answer the above science questions are also applicable beyond astrophysics to various technological challenges presented by e.g. Big Data and super-resolution imaging in medicine, biology, and engineering. Team members will receive training through research in the top five skills needed in the 2020s landscape: complex problem solving, critical thinking, creativity, people management, and coordinating with others. The outcomes of this project and astrophysics in general can spark the interest of the public and serve as a gateway, particularly in young people, to scientific concepts in STEM.
The ERC program ArcheoDyn consists of three projects. The first and second projects employ the stellar fossil record inside globular clusters (GCs) within the Milky Way, whereas the third project uses GCs as living fossils of the hierarchical build-up of galaxies.
Project 1: Robust dynamical inference of intermediate-mass black holes in globular clusters
We explored a sample of high-end Monte Carlo simulations of GCs, with and without a central IMBH, to investigate to what degree commonly-used dynamical models can infer an IMBH. We found that these models are reliable for a high-mass IMBH, but they lack the sensitivity to measure a low-mass IMBH. In parallel, we showed that an IMBH will not only halt the segregation of stellar binaries towards the cluster center, but also, directly and indirectly, disrupt the binaries that segregate. We thus predict that GCs with a relatively low fraction of binaries in the core and/or where the central velocity dispersion is not artificially increased due to binaries, are strong candidates to host an IMBH. With the crucial and novel insights achieved, we are now in the ideal position to robustly infer the presence of IMBHs in GCs.
Project 2: Dynamically uncovering the origin of multiple populations in globular clusters
Three sets of results have successfully been completed related to this project. Firstly, a detailed analysis and modeling of the kinematics, ages and metallicities of several thousand stars in the globular cluster M54 revealed the presence of a centrally concentrated metal-rich young population which likely formed as the result of a strong tidal interaction with the Milky Way. Secondly, population-dynamical modeling of the GC M80 suggests that the three chemically-distinct populations must have formed with primordial kinematic differences: a novel constraint on the origin of this phenomenon. Thirdly, development and validation of our new population-orbit modeling. First applications to nearby galaxies already yield high-impact results and promise further insights when using the latest GC datasets.
Project 3: Dynamically recovering satellite galaxy mergers via their surviving globular clusters
The problem is being tackled from different and complementary sides: combining (1) theoretical studies on the information needed to recover the gravitational potential with accreted globular clusters, (2) simulations to develop, verify, as well as understand the caveats in novel methodologies, and (3) observations to gain insight into the formation histories of individual galaxies. This multi-faceted approach already yielded several new insights. Firstly, with a sample of more than 150 GCs the dark matter halo properties are well recovered and even the shape can be constrained to be non-spherical. Secondly, combining high-quality dataset of velocities and metallicities of hundreds of GCs with detailed stellar population analysis of nuclear star clusters (NSCs) establishes a transition in the dominant NSC formation channel with galaxy mass: NSCs in low-mass galaxies predominantly grow through the inspiral of GCs, while central star formation can contribute to NSC growth in more massive galaxies. Combining our model that explains the latter transition with our novel method to unveil a galaxy's accretion history from an integrated-light spectra, will enable us to infer the assembly history, including ancient satellite mergers, of individual galaxies.
Project 1: Robust dynamical inference of intermediate-mass black holes in globular clusters
We explored a sample of high-end Monte Carlo simulations of GCs, with and without a central IMBH, to investigate to what degree commonly-used dynamical models can infer an IMBH. We found that these models are reliable for a high-mass IMBH, but they lack the sensitivity to measure a low-mass IMBH. In parallel, we showed that an IMBH will not only halt the segregation of stellar binaries towards the cluster center, but also, directly and indirectly, disrupt the binaries that segregate. We thus predict that GCs with a relatively low fraction of binaries in the core and/or where the central velocity dispersion is not artificially increased due to binaries, are strong candidates to host an IMBH. With the crucial and novel insights achieved, we are now in the ideal position to robustly infer the presence of IMBHs in GCs.
Project 2: Dynamically uncovering the origin of multiple populations in globular clusters
Three sets of results have successfully been completed related to this project. Firstly, a detailed analysis and modeling of the kinematics, ages and metallicities of several thousand stars in the globular cluster M54 revealed the presence of a centrally concentrated metal-rich young population which likely formed as the result of a strong tidal interaction with the Milky Way. Secondly, population-dynamical modeling of the GC M80 suggests that the three chemically-distinct populations must have formed with primordial kinematic differences: a novel constraint on the origin of this phenomenon. Thirdly, development and validation of our new population-orbit modeling. First applications to nearby galaxies already yield high-impact results and promise further insights when using the latest GC datasets.
Project 3: Dynamically recovering satellite galaxy mergers via their surviving globular clusters
The problem is being tackled from different and complementary sides: combining (1) theoretical studies on the information needed to recover the gravitational potential with accreted globular clusters, (2) simulations to develop, verify, as well as understand the caveats in novel methodologies, and (3) observations to gain insight into the formation histories of individual galaxies. This multi-faceted approach already yielded several new insights. Firstly, with a sample of more than 150 GCs the dark matter halo properties are well recovered and even the shape can be constrained to be non-spherical. Secondly, combining high-quality dataset of velocities and metallicities of hundreds of GCs with detailed stellar population analysis of nuclear star clusters (NSCs) establishes a transition in the dominant NSC formation channel with galaxy mass: NSCs in low-mass galaxies predominantly grow through the inspiral of GCs, while central star formation can contribute to NSC growth in more massive galaxies. Combining our model that explains the latter transition with our novel method to unveil a galaxy's accretion history from an integrated-light spectra, will enable us to infer the assembly history, including ancient satellite mergers, of individual galaxies.
Four novel and unconventional methodologies have thus far been developed with support of the ERC project ArcheoDyn.
Firstly, a novel method to unveil a galaxy's accretion history from its integrated spectrum (see https://ui.adsabs.harvard.edu/abs/2020MNRAS.491..823B/abstract).
Secondly, a new methodology for performing population-orbit superposition of stellar systems (see https://ui.adsabs.harvard.edu/abs/2020arXiv200305561Z/abstract) with already several applications leading to high-impact results.
Thirdly, the development of new statistical and computational techniques to robustly quantify uncertainties in our stellar population and dynamical methodologies and to reduce the sensitivity of results to arbitrary choices of regularization.
Last, but not least, the entire ArechoDyn team is involved in the development of the publicly available software package named DYNAMITE (see https://github.com/dynamics-of-stellar-systems/dynamite). This code brings together all of the above novel methodologies into a centralized tool for population-orbital decomposition of stellar systems.
Firstly, a novel method to unveil a galaxy's accretion history from its integrated spectrum (see https://ui.adsabs.harvard.edu/abs/2020MNRAS.491..823B/abstract).
Secondly, a new methodology for performing population-orbit superposition of stellar systems (see https://ui.adsabs.harvard.edu/abs/2020arXiv200305561Z/abstract) with already several applications leading to high-impact results.
Thirdly, the development of new statistical and computational techniques to robustly quantify uncertainties in our stellar population and dynamical methodologies and to reduce the sensitivity of results to arbitrary choices of regularization.
Last, but not least, the entire ArechoDyn team is involved in the development of the publicly available software package named DYNAMITE (see https://github.com/dynamics-of-stellar-systems/dynamite). This code brings together all of the above novel methodologies into a centralized tool for population-orbital decomposition of stellar systems.