Galactic and Extragalactic Astrophysics

3.

External Galaxies: Islands of Stars

3.1.

Galaxy Classification

3.1.1.

The Hubble Sequence

3.1.1.1.

Historical Development

3.1.1.2.

Morphological Criteria

3.1.1.3.

Limitations and Modern Extensions

3.1.2.

Elliptical Galaxies

3.1.2.1.

Shape and Flattening

3.1.2.2.

Surface Brightness Profiles

3.1.2.3.

3.1.3.

Lenticular Galaxies

3.1.3.1.

Disk and Bulge Properties

3.1.3.2.

Transitional Features

3.1.3.3.

S0a, S0b, S0c Subtypes

3.1.4.

Spiral Galaxies

3.1.4.1.

3.1.4.1.1.

Bar Structure and Dynamics

3.1.4.1.2.

Bar Fraction Evolution

3.1.4.2.

Unbarred Spirals

3.1.4.3.

3.1.4.3.1.

Bulge-to-Disk Ratio

3.1.4.3.2.

Arm Tightness and Star Formation

3.1.4.3.3.

3.1.5.

Irregular Galaxies

3.1.5.1.

Morphological Diversity

3.1.5.2.

Star Formation Activity

3.1.5.3.

Magellanic Type

3.1.6.

3.1.6.1.

Dwarf Spheroidal

3.1.6.1.1.

Low Surface Brightness

3.1.6.1.2.

Dark Matter Content

3.1.6.1.3.

Local Group Examples

3.1.6.2.

Dwarf Elliptical

3.1.6.2.1.

Nucleated vs. Non-nucleated

3.1.6.3.

Dwarf Irregular

3.1.6.3.1.

Gas Content and Star Formation

3.1.6.3.2.

Blue Compact Dwarfs

3.1.6.4.

Ultra-Compact Dwarfs

3.1.7.

Peculiar and Interacting Galaxies

3.1.7.1.

Merger Signatures

3.1.7.2.

3.1.7.3.

3.2.

Properties of Spiral Galaxies

3.2.1.

Disk, Bulge, and Halo Components

3.2.1.1.

Structural Parameters

3.2.1.2.

Stellar and Gas Content

3.2.1.3.

Exponential Disk Profiles

3.2.2.

Star Formation Rates

3.2.2.1.

3.2.2.2.

Environmental Dependence

3.2.2.3.

Star Formation Laws

3.2.3.

Gas Content and Distribution

3.2.3.1.

Atomic and Molecular Gas

3.2.3.2.

Radial Gas Profiles

3.2.3.3.

Gas Depletion Times

3.2.4.

Rotation Curves and Dark Matter

3.2.4.1.

Observational Techniques

3.2.4.2.

3.2.4.3.

Baryonic Tully-Fisher Relation

3.2.5.

Spiral Arm Properties

3.2.5.1.

Arm Classification

3.2.5.2.

Star Formation Efficiency

3.2.5.3.

Density Contrast

3.3.

Properties of Elliptical Galaxies

3.3.1.

Stellar Kinematics

3.3.1.1.

Pressure vs. Rotation Support

3.3.1.2.

Velocity Dispersion Profiles

3.3.1.3.

3.3.1.4.

Kinematic Substructure

3.3.2.

3.3.2.1.

3.3.2.2.

Cooling and Heating Processes

3.3.2.3.

3.3.3.

Stellar Populations

3.3.3.1.

Old and Metal-Rich

3.3.3.2.

Age and Metallicity Gradients

3.3.3.3.

Alpha-element Enhancement

3.3.4.

Fundamental Plane

3.3.4.1.

Scaling Relations

3.3.4.2.

Implications for Formation

3.3.4.3.

Tilt and Scatter

3.3.5.

Central Black Holes

3.3.5.1.

Mass Scaling Relations

3.3.5.2.

Activity Levels

3.4.

Galaxy Luminosity and Mass Functions

3.4.1.

The Schechter Luminosity Function

3.4.1.1.

Mathematical Formulation

3.4.1.2.

Observational Determination

3.4.1.3.

Evolution with Redshift

3.4.2.

3.4.2.1.

Stellar Mass Function

3.4.2.2.

Halo Mass Function

3.4.3.

Mass-to-Light Ratios

3.4.3.1.

Stellar vs. Total Mass

3.4.3.2.

Variation with Galaxy Type

3.4.3.3.

Dark Matter Fractions

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