## AST 301: Introduction to Astrophysics

3 credits | Prerequisites: AST 201 for A&A Minor; PHY 101, MAT 104 for Physics Minor

### Course rationale

This is an elective course designed for students majoring in physics, mathematics, engineering or computer science. Students can take it as part of a minor or specialization in astronomy and astrophysics or as a free elective. The course intends to give an overview of the theoretical understanding and observational evidence of our current picture of the universe and its large-scale constituents. However, more emphasis will be put on astrophysical observations than theory. For a more rigorous theoretical approach to cosmology, please refer to PHY 402: Cosmology.

### Course content

Observing the universe: fundamental cosmological observations and their consequences: Olber’s paradox, homogeneity and isotropy, recession of galaxies, abundance of helium, age of globular clusters, CMB anisotropies, number counts of radio galaxies. Standard model of cosmology: Newtonian cosmology, kinematics and dynamics of the universe, laws of thermodynamics. Expansion equations: Friedmann-Lemaître equations and their consequences, big bang, age of the universe, redshift, Einstein-de Sitter model. Thermal history of the universe: radiation-dominated phase, decoupling of neutrinos, pair annihilation, primordial nucleosynthesis, deuterium formation, helium abundance, baryons and dark matter. Blackbody radiation: Planck’s law, Rayleigh-Jeans and Wien approximations, luminosity of a spherical black body, radiation pressure, limits of intensity. Cosmic microwave background: recombination, origin of CMB, dipole anisotropy, spectral evolution, temperature anisotropy, angular fluctuations, polarization. Formation of structures: galaxy redshift surveys, gravitational instability, linear perturbation theory, density fluctuations, correlation functions, power spectrum. Evolution of structures: the initial power spectrum, growth of density perturbations, cold and hot dark matter, spherical collapse, dark matter haloes, numerical simulations of structure formation, substructures, peculiar velocities. Hydrogen spin-flip radiation: Sky at 1420 MHz or 21 cm, quantization fundamentals, hyperfine transition: line splitting, the interaction terms, magnetic field inside proton, spin-spin coupling, energy difference, Zeeman effect. Dark ages and cosmic dawn: galaxies at high redshift, active and starburst galaxies, galaxy formation and evolution, cosmic star-formation history. Epoch of reionization: the first stars, the reionization process, detection of the 21-cm signal from this epoch. Cosmological parameters: determining cosmological parameters using observations: CMB, distant supernovae, cosmic shear, Lyman-α forest, intensity mapping of hydrogen.

### Course objectives

- Understand the observational basis of our current standard model of the universe.
- Describe the evolution of the early universe until formation of stars and galaxies using equations of motion.
- Introduce the physical mechanisms behind the continuum blackbody radiation and the 21-cm line radiation.
- Extract scientifically useful information from cosmic blackbody and 21-cm radiation.
- Understand the importance of the radiation of 21-cm wavelength from hydrogen in creating a 4D map of the universe.

### References

- Peter Schneider, Extragalactic Astronomy and Cosmology: An Introduction, Springer, 2006.
- Andre Liddle, An Introduction to Modern Cosmology, 3rd edition, Wiley, 2015.
- Hale Bradt, Astrophysics Processes: The Physics of Astronomical Phenomena, Cambridge University Press, 2008.
- Bradley Carroll & Dale Ostlie, An Introduction to Modern Astrophysics, 2nd edition, Cambridge University Press, 2017.