Short Option S26 - Stars and Galaxies

Dr. Andrew Bunker

9am Mondays and Tuesdays, 10am Wednesdays weeks 1-4 Trinity Term 2014 (Lindemann Lecture Theatre)

Syllabus

Measurement of physical properties of stars and galaxies. Parallax and the distance ladder. Magnitude systems and their relationship to quantitative measurements of luminosity and effective temperature. Observational properties of stars and galaxies: the H-R diagram, stellar clusters, basic description of the structure of the Milky Way; the Hubble classification of galaxies; galaxy luminosity functions.

The equations of stellar structure: hydrostatic equilibrium, virial theorem, convection and energy transport. Structure of main sequence stars; use of scaling relations to derive relationships between stellar masses, luminosities, radii and lifetimes. The Chandrasekar limit and degenerate stellar cores; introduction to post-main sequence evolution.

Galaxies treated as systems of stars in spherically symmetric gravitational potentials. The Collisionless Boltzmann Equation; Jeans' equations; moments of distributions. Stellar velocity dispersions and their use to infer the potential. Influence of a point mass at the centre of the potential; observational evidence for supermassive black holes in normal galaxies.

Textbooks

There is not really a course textbook, but the following are useful:
Astrophysics for Physicists - A.R. Choudhuri (2010, Cambridge University Press)
An Introduction to Modern Astrophysics - B.W. Carroll & D. Ostlie (Second Edition 2007, Pearson/Addison Wesley),
Galaxies in the Universe - L.S. Sparke & J.S. Gallagher (2000, Cambridge University Press)
Galactic Dynamics - J. Binney & S. Tremaine (Second Edition Princeton University Press) - Note this book is graduate-level and goes well beyond this course

Lecture Outline

The actual split of topics between lectures may change. Lecture notes will be posted here shortly (PDF format). NOTE: Lecture notes only available within the Oxford network!

  • Lecture 1 Lecture notes (PDF). Lecture slides (PDF). Unit of length, parallax, definition of parsec (Choudhuri 1.1). Luminosity and flux, f=L/(4*PI*r^2). Solar units. Dependence of luminosity on effective temperature of star, L=sigma*T^4 * 4*PI*r^2 . Magnitude definition, absolute and apparent magnitudes (Choudhuri 1.5) and the relation m-M=5log10(d/pc)-5. Observations, different wavebands (Choudhuri 1.7) Effect of dust on distance estimates
  • Lecture 2 Lecture notes (PDF). Lecture slides (PDF) Spectral classification introduction - surface temperature of stars and spectral characteristics. The Hertzsprung-Russell (HR) diagram and its key features. The Main Sequence (MS), and the MS turn-off in stellar clusters. MS lifetime. Age and metallicity.
  • Lecture 3 Lecture notes (PDF). Lecture slides (PDF) Basic description of the structure of the Milky Way (the thin and thick disk, bulge, halo and globular clusters); Population I and II stars. Gas and dust. Determining the size and shape of our galaxy. The mass in stars, and the dynamical mass. Spiral arms and Galactic rotation. Evidence for a central Black Hole.
  • Lecture 4 Lecture notes (PDF). Lecture slides (PDF) The Hubble classification of galaxies; Nature of elliptical and spiral galaxies - sub-classes, surface brightness profiles and mass estimates. Colours of different galaxies, and abundance of gas, dust and star formation. The Tully-Fisher relation for spirals, and the Faber-Jackson and Kormendy relations for ellipticals (the Fundamental Plane). The winding problem for spiral arms. Evidence for dark matter. The galaxy luminosity function. Galaxy interactions and galaxy evolution.
  • Lecture 5 Lecture notes (PDF). Lecture slides (PDF) Hydrostatic equilibrium, dP/dr = -G*M*rho/r^2 (Choudhuri 3.2). Estimate of central pressure and temperature (and caveats). Timescales of stars and virial theorem for stars
  • Lecture 6 Lecture notes (PDF). Lecture slides (PDF) Energy sources of stars. Energy transport: radiation L=-4*PI*r^2*4*a*c/(3*kappa*rho)*T^3*dT/dr convection dT/dr=(gamma-1)/gamma*T/P*dP/dr . opacity and optical depth. Stellar models (Choudhuri 3.3). Ideal gas, and mean particle mass (concept of X,Y,Z abundance). Scaling relations (Choudhuri 3.4) e.g. HR main sequence, M-L relation.
  • Lecture 7 Lecture notes (PDF). Lecture slides (PDF) Binding energy, nuclear reaction rates (Choudhuri 4.1). PPI chain, CNO cycle, Helium triple-alpha (Choudhuri 4.2). Chemical enrichment, alpha-elements.
  • Lecture 8 Lecture notes (PDF). Lecture slides (PDF) Stellar evolution - main sequence, turn-off, red giant branch (AGB), helium flash, horizontal branch, asymptotic-AGB, planetary nebula (Choudhuri 4.5).
  • Lecture 9 Lecture notes (PDF). Lecture slides (PDF) White dwarfs - degenerate gas,relativistic and non-relativistic (Choudhuri 5.2,5.3). Stellar evolution of high mass stars: shell model, burning higher mass nuclei until iron core, Type II supernovae Neutron star Chandrasekhar mass, Schwarzschild black holes
  • Lecture 10 Lecture notes (PDF). Lecture slides (PDF) Galaxy dynamics - galaxies treated as systems of stars in spherically symmetric gravitational potentials. The Collisionless Boltzmann Equation; Jeans' equations; moments of distributions.
  • Lecture 11 Lecture slides (PDF) Stellar collisions and relaxed systems.
  • Lecture 12 Lecture slides (PDF) Summary of course (except Galaxy Dynamics in previous 2 lectures)

Example Problems

Problem set 1 (PDF)

Problem set 2 (PDF)

Relevant Longer Problems (PDF) from my similar course on Galaxies at University of Exeter (Finals questions)

Contact

Questions can be emailed to the lecturer.