Galactic and Extragalactic Astrophysics

Galactic and Extragalactic Astrophysics is the branch of physics that investigates the formation, structure, evolution, and dynamics of galaxies, both our own Milky Way and the billions of others that populate the universe. This field applies the principles of gravity, thermodynamics, and nuclear physics to understand the collective behavior of stars, gas, dust, and dark matter that constitute these massive systems. Researchers in this area study everything from the stellar populations and interstellar medium within the Milky Way to the large-scale cosmic web formed by galaxy clusters and superclusters, providing a crucial link between the life cycles of individual stars and the overall history and structure of the cosmos.

1. Foundational Concepts and Observational Tools
   1. The Cosmic Distance Ladder
      1. Parallax Methods
         1. Trigonometric Parallax
            1. Geometric Principles
            2. Limitations and Range
            3. Space-based Parallax Missions
            4. Error Analysis and Systematic Effects
         2. Statistical Parallax
            1. Application to Stellar Populations
            2. Uncertainties and Assumptions
            3. Moving Cluster Method
      2. Standard Candles
         1. Cepheid Variables
            1. Period-Luminosity Relation
            2. Classical vs. Type II Cepheids
            3. Calibration Techniques
            4. Use in Extragalactic Distances
            5. Metallicity Effects
         2. RR Lyrae Variables
            1. Characteristics and Distribution
            2. Role in Galactic Structure Studies
            3. Horizontal Branch Evolution
         3. Type Ia Supernovae
            1. Light Curve Standardization
            2. Phillips Relation
            3. Cosmological Distance Measurements
            4. Systematic Uncertainties
         4. Tully-Fisher Relation
            1. Spiral Galaxy Rotation and Luminosity
            2. Calibration and Scatter
            3. Baryonic Tully-Fisher Relation
         5. Faber-Jackson Relation
            1. Elliptical Galaxy Velocity Dispersion and Luminosity
            2. Applications and Limitations
            3. Fundamental Plane Extension
         6. Surface Brightness Fluctuations
            1. Physical Basis
            2. Application to Early-type Galaxies
         7. Planetary Nebula Luminosity Function
            1. Standardization Method
            2. Distance Range
      3. Standard Rulers
         1. Physical Basis
         2. Baryon Acoustic Oscillations
            1. Sound Horizon Scale
            2. Galaxy Clustering Signatures
         3. Angular Diameter Distance
            1. Geometric Distance Measurement
      4. Redshift and Hubble's Law
         1. Doppler Effect and Cosmological Redshift
         2. Hubble Constant Determination
            1. Local Distance Ladder
            2. Early Universe Methods
            3. Hubble Tension
         3. Peculiar Velocities
            1. Local Group Motion
            2. Bulk Flows
         4. Distance-Redshift Relation
            1. Linear and Non-linear Regimes
   2. Observational Techniques
      1. Multi-wavelength Astronomy
         1. Radio Astronomy
            1. Radio Telescopes and Interferometry
            2. Synchrotron and Thermal Emission
            3. 21-cm Line Observations
            4. Molecular Line Spectroscopy
         2. Infrared Astronomy
            1. Atmospheric Windows
            2. Dust Penetration and Star Formation
            3. Thermal Emission from Dust
            4. Space-based IR Missions
         3. Optical Astronomy
            1. Ground-based and Space-based Observations
            2. Photometric Systems
            3. Adaptive Optics
            4. Large Survey Telescopes
         4. Ultraviolet Astronomy
            1. Space-based UV Telescopes
            2. Hot Star and AGN Studies
            3. Interstellar Absorption
         5. X-ray and Gamma-ray Astronomy
            1. High-energy Detectors
            2. Emission from Hot Gas and Compact Objects
            3. Focusing and Non-focusing Instruments
      2. Spectroscopy
         1. Principles of Spectral Analysis
            1. Doppler Shifts and Line Profiles
            2. Instrumental Resolution
         2. Stellar and Gas Kinematics
            1. Radial Velocity Measurement
            2. Rotation Curves
            3. Velocity Dispersion
            4. Proper Motion Studies
         3. Chemical Abundance Measurement
            1. Absorption and Emission Lines
            2. Metallicity Indicators
            3. Abundance Ratios
         4. Redshift Determination
            1. Spectral Line Identification
            2. Cosmological Implications
            3. Photometric Redshifts
      3. Photometry
         1. Photometric Systems and Filters
            1. Broadband and Narrowband Filters
            2. Magnitude Systems
         2. Color-Magnitude Diagrams
            1. Stellar Evolution Tracing
            2. Population Analysis
            3. Distance Modulus Determination
         3. Surface Brightness Profiling
            1. Galaxy Structure Analysis
            2. Bulge-Disk Decomposition
            3. Sérsic Profile Fitting
      4. Astrometry
         1. Proper Motion Measurements
         2. Parallax Determination
         3. Reference Frame Systems
   3. Fundamental Physics in a Galactic Context
      1. Gravitational Dynamics
         1. Newtonian Gravity and Potentials
            1. Two-body and N-body Problems
            2. Gravitational Binding Energy
            3. Tidal Forces
         2. Virial Theorem
            1. Application to Star Clusters and Galaxies
            2. Mass Estimation Techniques
            3. Equilibrium Conditions
         3. Collisionless vs. Collisional Systems
            1. Relaxation Timescales
            2. Examples: Stars vs. Gas
            3. Phase Space Density Conservation
         4. Orbital Dynamics
            1. Kepler's Laws
            2. Epicyclic Motion
            3. Resonances
      2. Stellar Evolution and Populations
         1. Hertzsprung-Russell Diagram
            1. Main Sequence, Giants, and White Dwarfs
            2. Isochrones and Age Dating
            3. Stellar Tracks
         2. Main Sequence Lifetimes
            1. Mass-Luminosity Relation
            2. Stellar Lifespan Estimates
            3. Nuclear Burning Phases
         3. Post-Main Sequence Evolution
            1. Red Giants and Supergiants
            2. Asymptotic Giant Branch
            3. Planetary Nebulae and Supernovae
            4. Remnants: White Dwarfs, Neutron Stars, Black Holes
         4. Stellar Population Synthesis
            1. Simple and Composite Stellar Populations
            2. Initial Mass Function
            3. Integrated Light Modeling
            4. Population Age and Metallicity Effects
      3. Interstellar Physics
         1. Radiative Transfer
            1. Absorption, Emission, and Scattering
            2. Optical Depth
         2. Thermal Balance
            1. Heating and Cooling Processes
            2. Temperature Structure
         3. Magnetohydrodynamics
            1. Magnetic Field Effects
            2. Plasma Physics