Galaxies Part II Observations of Globular Clusters King Models Ja↵e Model Stellar Dynamics and Structure of Galaxies Systems with anisotropic velocity distributions Star Clusters Modelling Cluster Evolution Globular cluster evolution Vasily Belokurov [email protected] Institute of Astronomy Lent Term 2016 1/93 Galaxies Part II Outline I Observations of Globular Clusters 1 Observations of Globular Clusters King Models The Great Debate Ja↵e Model Galactic Structure Systems with anisotropic Properties of globular clusters velocity distributions Star Cluster Formation Modelling Cluster Evolution Star Cluster Disruption Globular cluster evolution 2 King Models 3 Ja↵e Model 4 Systems with anisotropic velocity distributions 5 Modelling Cluster Evolution 6 Globular cluster evolution Relaxation times Relaxation Escape of Stars Core collapse Mass segregation Tidal stripping 2/93 Galaxies Part II Outline II Observations of Globular Clusters Encounters with Binary Stars King Models Binary Formation through inelastic encounters Ja↵e Model Finally Systems with anisotropic velocity distributions Modelling Cluster Evolution Globular cluster evolution 3/93 Galaxies Part II Globular Clusters Observations of Globular Clusters The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Globular clusters are approximately spherical, compact agglomerations of stars Ja↵e Model swarming around galaxies. They are as old as the galaxies themselves and provide Systems with anisotropic velocity distributions unique clues to how the star formation and the galaxy formation proceeded in the Modelling Cluster ancient Universe. Evolution Globular cluster evolution Being old, spherical and devoid of Dark Matter, globular clusters are perfect environments to learn about the gravity works. 4/93 Galaxies Part II Observations of Globular Clusters The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model Systems with anisotropic velocity distributions Modelling Cluster Evolution Globular cluster evolution M15, Hubble 5/93 Galaxies Part II Observations of Globular Clusters The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model Systems with anisotropic velocity distributions Modelling Cluster Evolution Globular cluster evolution Top row: Messier 4 (ESO), Omega Centauri (ESO), Messier 80 (Hubble) Middle row: Messier 53 (Hubble), NGC 6752 (Hubble), Messier 13 (Hubble) Bottom row: Messier 4 (Hubble), NGC 288 (Hubble), 47 Tucanae (Hubble) 6/93 Galaxies Part II The Great Debate Observations of Globular Clusters 26 April 1920, in the Baird auditorium of the Smithsonian Museum of Natural History. The Great Debate Galactic Structure Properties of globular “The Scale of the Universe” clusters Star Cluster Formation Harlow Shapley Heber Curtis Star Cluster Disruption King Models The nebulae are part of the large Milky The nebulae are “Island Universes” located Ja↵e Model Way system at large distances away from the Galaxy Systems with anisotropic velocity distributions Modelling Cluster Evolution Globular cluster evolution 7/93 Galaxies Part II The Great Debate Observations of Globular Clusters The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Vesto Melvin Slipher measured wavelength shifts of spiral nebulae Ja↵e Model • Systems with anisotropic Johannes C. Kapteyn advertised a small Milky Way centered on the Sun velocity distributions • Modelling Cluster Adriaan van Maanen measured apparent rotation of spiral galaxies Evolution • Knut Lundmark speculated that the dwarf novae might be so bright as to be Globular cluster evolution • detectable millions of light years from us 8/93 Galaxies Part II The Great Debate Observations of Globular Clusters The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model Shapley believes the Galaxy is tens of kpc across. “If spiral galaxies are like Systems with anisotropic • velocity distributions islands, then the Galaxy is a continent” Modelling Cluster Evolution Curtis’s Milky Way is much smaller, only 10 kpc across Globular cluster evolution • 9/93 Galaxies Part II The Great Debate Observations of Globular Clusters Resolved F, G and K stars in globular clusters. Shapley: these are giants, Curtis: The Great Debate • Galactic Structure these are dwarfs. Properties of globular clusters Cepheids as distance indicators. Shapley: there is P-L relation. Curtis: parallaxes are Star Cluster Formation • Star Cluster Disruption too small, “more data needed”. King Models Spectroscopic parallaxes. Shapley: these are to be trusted. Curtis: to be trusted only • Ja↵e Model within 100 pc. Systems with anisotropic Interpretation of the star counts. Curtis: star counts suggest small MW, but would velocity distributions • Modelling Cluster place the dust outside the stellar disk. Shapley: did not address the issue. Evolution Distribution of spiral nebulae on the sky. Shapley: “single system” - all is possible. • Globular cluster evolution Curtis: “neither impossible nor implausible” for the MW to have a dust ring around it. Nova brightness at maximum. Shapley: the implied real brightnesses would be totally • ridiculous. Curtis: trust the calibration based on a handful of MW events. Large positive velocities of spiral nebulae. Shapley: repulsion by radiation pressure • form the MW. Curtis: “I haven’t a clue” Central location of the Sun. Shapley: an illusion caused the local star cloud. Curtis: • this is God’s own truth Rotational proper motions of spirals as measured by van Maanen. Shapley: a • strong argument against opponent. Curtis: too dodgy 10 / 93 Galaxies Part II The Great Debate Observations of Globular Clusters The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model The outcome? Systems with anisotropic velocity distributions Both were mainly right, but also impressively wrong in some very important points. • Modelling Cluster Right when relying on their own data, and wobbly when attempting to speculate Evolution • Globular cluster evolution based on the current theory. 11 / 93 Galaxies Part II The Great Debate Observations of Globular Clusters The State of the Art The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model Systems with anisotropic velocity distributions Modelling Cluster Evolution Globular cluster evolution 12 / 93 Galaxies Part II The Great Debate Observations of Globular Clusters The State of the Art The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model Systems with anisotropic velocity distributions Modelling Cluster Evolution Globular cluster evolution 13 / 93 Galaxies Part II The Great Debate Observations of Globular Clusters The State of the Art The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model Systems with anisotropic velocity distributions Modelling Cluster Evolution Globular cluster evolution Trumpler’s Galaxy with the Sun in the middle of Kapteyn Universe 14 / 93 Galaxies Part II The Great Debate Observations of Globular Clusters The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model Shapley: The Sun lies in a nondescript location in the Galaxy. Systems with anisotropic velocity distributions Modelling Cluster This is a key part to a bigger Copernican Principle, that we live neither in the centre of Evolution the Solar System, our Galaxy, nor the Universe as a whole. Globular cluster evolution 15 / 93 Galaxies Part II The Role of Star Clusters Observations of Globular Clusters The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model Galaxy structure Systems with anisotropic • velocity distributions Galaxy formation • Modelling Cluster Evolution Stellar evolution • Globular cluster evolution Star formation • 16 / 93 Galaxies Part II Galactic Structure Observations of Globular Clusters The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model Systems with anisotropic velocity distributions Modelling Cluster Evolution Globular cluster evolution Portegies Zwart et al, 2010 17 / 93 Galaxies Part II Galactic Structure Observations of Globular Clusters The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model Systems with anisotropic velocity distributions Modelling Cluster Evolution Globular cluster evolution M. Irwin and PAndAS collaboration 18 / 93 Galaxies Part II Number of Globular Clusters per galaxy Observations of Globular Clusters The Great Debate Galactic Structure Properties of globular clusters Star Cluster Formation Star Cluster Disruption King Models Ja↵e Model Systems with anisotropic Milky Way: 100 < N < 200 velocity distributions • Andromeda: 200 < N < 500 Modelling Cluster • Evolution M 87: N > 1000 Globular cluster evolution • 19 / 93 Galaxies Part II Number of Globular Clusters