Properties of Galaxies
Spring 2002
    Unique No. 45655 TTH 12:30-2:00 RLM 15.216B


Note: The origin and early evolution of fluctuations belongs in the Cosmology course. Some discussion of hierarchical clustering and the formation of large-scale structure is inevitable here, because the study of galaxy formation cannot be removed from its cosmological context. Basically, the aim here is to discuss galaxy formation starting at a time when individual objects are well separated from the expansion of the universe.

8.1 Introduction

  • Eggen, Lynden-Bell, & Sandage (1962)
  • Hydrodynamic collapse simulations

8.2 Galaxy Mergers:Theory

  • Dynamical friction and orbital decay
  • Chandrasekhar’s formula
  • Implications:
    • Toomre’s hypothesis that all bulges and ellipticals are merger remnants
    • Galaxy formation must be studied in the context of large-scale structure formation
  • Conservation of phase space density

8.3 Simulations of Hierarchical Clustering and Galaxy Formation

  • Cold dark matter simulations
    • Properties of the galaxies that form
    • Comparison with observations:successes and failures
  • Dissipationless simulations of group and binary mergers
    • Properties of the galaxies that form
    • Comparison with observations: successes and failures
  • The need for dissipation
  • Dissipational simulations of group and binary mergers
    • Properties of the galaxies that form
    • Comparison with observations: successes and failures

8.4 Observational Constraints on Galaxy Formation

  • Observations of mergers in progress
    • Merger sequence from close binary galaxies --> violence --> remnants
  • Starbursts: IRAS galaxies
  • Possible connection between ultraluminous IRAS galaxies and quasars
  • Recognizing old mergers: tails, shells, and other fine structure
  • Recognizing completed mergers: embedded stellar disks
    • Photometric signatures
    • Kinematic signatures
  • Small accretion events
    • Not every elliptical with fine structure needs to be a major merger remnant

8.5 Tentative Verdict: Mergers versus Dissipative Collapse

  • Strengths and weaknesses of the merger picture
  • Evidence from high-z galaxies
  • Bottom line: both mergers and dissipative collapse were important

8.6 Physical Processes During Galaxy Formation:Origin of the Fundamental Plane

  • Dissipation: cooling times and galactic scales
  • Complications: energy input during starbursts, etc.
  • Formation of ellipticals
  • Rotation of disk galaxies
  • Late infall of cold gas
  • Ongoing problems
  • Connections with observations at high z

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30 October 2001
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