Letters of Intent for 2014

LoI 2014-144
Star Clusters and Black Holes in Galaxies across Cosmic Time

Date:

25 August 2014 to 29 August 2014

Location:

Beijing, National Library of CAS, Hong Kong

Contact:

Rainer Spurzem (spurzem@nao.cas.cn)

Coordinating division:

Division VII Galactic System

Co-Chairs of SOC:

Fukun LIU (Dep. of Astronomy/KIAA, School of Physics, Peking University)
Rainer SPURZEM (National Astronomical Observatories Chinese Academy of Sciences)

Co-Chairs of LOC:

Rainer SPURZEM (National Astronomical Observatories Chinese Academy of Sciences)
Fukun LIU (Dep. of Astronomy, School of Physics/KIAA, Peking University)

 

Topics

Note: See List of Confirmed SOC and LOC Members at the end.

* Black Holes in Galactic Nuclei - gravitational waves and electro-magnetic counterparts (determining their masses and spins, finding binary black holes, accretion disks, stellar tidal disruptions; computer simulation of galactic nuclei with black holes, compact high density star clusters around supermassive black holes)

* Recoiling Black Holes (ejected by relativistic merger recoils or Newtonian recoil, hypercompact stellat systems / gravitational waves, observations of kicked out AGN or BLR)

* Galaxy Mergers and AGN in the early universe

* Extragalactic and Galactic Globular Clusters (Theory and Observation, Globular Cluster Systems in general, in the Virgo cluster / near Antenna galaxies)

* Globular Star Clusters in the Local Group (Long Term Evolution and Observations), multiple populations, rotation, tidal fields, link to galactic halo)

* Nuclear Star Clusters and Transition to Dwarf Galaxies (Low mass end of m-sigma relation; massive globulars / stripped ultracompact dwarf nuclei / transition objects)

Core SOC Members: Fukun Liu (DoA/KIAA/PKU, Beijing, China, co-chair), Rainer Spurzem (NAOC, Beijing, China, co-chair), Joan Centrella (USA), Stefanie Komossa (Germany/China), Jufu Lu (Xiamen, China), Steve McMillan (Philadelphia, USA), Douglas Heggie (Edinburgh, UK), Giampaolo Piotto (Padova, Italy), Alison Sills (McMaster, Canada)

Core LOC Members: Fukun Liu (DoA/KIAA/PKU, co-chair), Rainer Spurzem (NAOC, co-chair), Licai Deng (NAOC), Eric Peng (KIAA/DoA), Thijs Kouwenhoven (KIAA), Lijun Gou (NAOC), Qingjuan Yu (KIAA), Youjun Lu (NAOC), Lixin Li (KIAA), Peter Berczik (NAOC), Gareth Kennedy (NAOC), Luca Naso (NAOC), Weimin Yuan (NAOC), Jifeng Liu (NAOC), Shuo Li (NAOC)

 

Rationale

(Note this Webpage contained the old divisions.)
Proposed Supporting Division:
Division J: Galaxies and Cosmology

Further Divisions with an interest:
Division D: High Energies and Fundamental Physics
Division G: Stars and Stellar Physics
Division H: Interstellar Matter and Local Universe

Star Clusters and Black Holes are getting into the focus of high-resolution astrophysics, computational as well as observational. cosmological models of galaxy formation in the universe reach for the first time down to the supermassive black holes forming and growing in the centers of galaxies by gas and star accretion. High star formation activity in the early universe leads to the formation of dense and very compact clusters of stars around them. Stars diffuse towards the deep central potential and finally get disrupted by tidal forces of the central black holes or direct stellar collisions. Gas settles after galaxy mergers in nuclear disks around supermassive black holes, which feed the central disk and jet engine of active galactic nuclei in the vicinity of the black hole. Relativistic dynamics of stars and gas couples to the large scales through energy and momentum feedback. This symposium should bring together experts in high resolution theoretical modelling and population studies as well as high resolution observations related to dynamical processes involving dense stellar systems, central gas in active and quiescent galactic nuclei, and black holes, across all wavelengths and instruments.

The problem gets even more challenging in the case of galaxy mergers; after major mergers gas and stars are rapidly transported towards the central region and a bound supermassive black hole binary may form. Its further evolution is determined by interactions with stars and gas, and ultimately gravitational radiation emission, during spiral-in and final relativistic coalescence. Electromagnetic counterparts of imminent gravitational wave emission from relativistic spiral-in and coalescence of black holes are highly sought after, in order to identify astrophysical sources of gravitational waves and give independent evidence. Recently it became clear that, depending on the original spins of the black holes, strong recoils can occur, which lead to excursions of supermassive black holes with all their counterparts (AGN, hypercompact stellar system, tidal disruptions of stars with X-ray flares, relativistic inspiral of stellar mass black holes) into the outer haloes of galaxies or even - if there are superkicks - into the intergalactic space. This symposium will cover the astrophysical determinants of black hole spins, and the evolution of binary black holes in gas-poor and gas-rich mergers, their final spins, recoils and possible ejections from galaxies.

Star clusters across cosmic time are also to be found in the outskirts of galaxies - at the lower mass end of the galaxy - black hole correlations. They are formed directly during mergers and strong star formation episodes, presumably low mass with little if any dark matter, but the most massive ones seem to form a continuous link with nuclei of ultra compact dwarf galaxies. Modeling of cluster formation and long-term evolution of globular and open star clusters has long been highly influenced by our well-known some hundred globular clusters in the Milky Way, in recent years complemented by many known globular clusters around Local Group galaxies, which can still be observed star-by-star. It is long known that external galaxies have systems of thousands of globular clusters, that especially merging seems to trigger globular cluster formation, and recently a huge amount of free floating globular clusters has been found by the Hubble Space Telescope between galaxies in the Virgo cluster. Our conventional approach of inverse dynamical synthesis of globular cluster formation needs update and improvement with respect to the wealth of new data coming in about extragalactic, extra-local-group globular clustes. Our planned symposium shall be the focal point to exchange first results in this direction as well as to discuss future research.

Last, but not least, there is NOT everything understood even in the small sample of our galactic globular clusters. Recent observations with highest resolutions show that they often show complex phenomena like multiple stellar populations and particular patterns in their giant branch in the Hertzsprung-Russell diagram. We are beginning to explore these features by theoretical modelling, and first insight hints on two dynamically distinct phases of star formation in clusters, with complex chemical evolution. Also the mass loss history of star clusters and their tidal arm features are clues to the structure of the galactic haloes they live in. Long term dynamical evolution of realistic globular star clusters with binaries, multiple populations, initial rotation and realistic tidal external fields are as well far from being completed right now. Their stellar populations develop compact objects such as white dwarfs, neutron stars and stellar mass black holes and binaries made of them. These are promising sources of gravitational waves detectable by ground-based instruments.

Star Clusters and Black Holes, galaxy mergers, star and cluster formation, high resolution observations of star clusters and galaxies across all redshifts as well as high resolution simulations of stellar systems with black holes and gas are the common topic of all these timely and actively growing subjects as described above. Novel instrumentation and simulation techniques may be also admitted as belonging to this symposium proposal as long as they have a direct impact on the scientific subjects here.

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