To be published by Cambridge University Press; Proceedings of the XXIII Canary Islands Winter School of Astrophysics: 'Secular Evolution of Galaxies', edited by J. Falcon-Barroso and J.H. Knapen 2012
astro-ph/1210.6990

For a PDF version of the article, click here.

EVOLUTION OF STAR FORMATION AND GAS

Nick Z. Scoville


California Institute of Technology
1200 East California Boulevard, Pasadena, CA 91125, USA

Abstract: In these lectures I review observations of star-forming molecular clouds in our Galaxy and nearby galaxies to develop a physical intuition for understanding star formation in the local and high-redshift Universe. A lot of this material is drawn from early work in the field since much of the work was done two decades ago and this background is not generally available in the present literature. I also attempt to synthesise our well-developed understanding of star formation in low-redshift galaxies with constraints from theory and observations at high redshift to develop an intuitive model for the evolution of galaxy mass and luminosity functions in the early Universe.

The overall goal of this contribution is to provide students with background helpful for analysis of far-infrared (FIR) observations from Herschel and millimetre/submillimetre (mm/submm) imaging with ALMA (the Atacama Large Millimetre/submillimetre Array). These two instruments will revolutionise our understanding of the interstellar medium (ISM) and associated star formation and galaxy evolution, both locally and in the distant Universe. To facilitate interpreting the FIR spectra of Galactic star-forming regions and high-redshift sources, I develop a model for the dust heating and radiative transfer in order to elucidate the observed infrared (IR) emissions. I do this because I am not aware of a similar coherent discussion in the literature.


Table of Contents

STAR-FORMING MOLECULAR CLOUDS
Background
Molecular excitation
Summary
Observed properties of molecular gas
Self-gravitating GMCs
Molecular masses from tau ≫ 1 CO emission
Lifetimes of GMCs
GMC supersonic internal motions
Summary

STAR FORMATION
Probes of star formation
Infrared emission
Dust optical depth: tau < 1 or tau > 1?
Dust temperature of the emergent luminosity
Star formation rate from LIR
Dust and ISM mass estimates
Effective source size
Luminosity and SFR estimates from submm continuum
Modelling optically-thick dust clouds
Summary

STAR FORMATION IN GALAXIES - TWO MODES
Quiescent or normal mode of star formation
Dynamically-driven starburst mode
Star formation `laws'
Distinguishing normal star formation and starbursts: concentration and timescales
Starbursts in ULIRGs
Arp 220 - a prototypical ULIRG
An aside: Sgr A* - an extraordinary ISM
Nuclear starburst disks
Maximum-rate starbursts - the dust Eddington limit
AGN - starburst: observational connections
AGN - starburst: theoretical connections

EVOLUTION OF GALAXIES AT HIGH REDSHIFT
Luminosity and Mass Functions
Environmental correlations

MODELLING STAR FORMATION AT HIGH REDSHIFT: SAME MODES BUT DIFFERENT FREQUENCY
Cosmic evolution: M* and MISM and star formation luminosities
Need ISM replenishment by accretion
ULIRG starbursts account for high-L tail

CONCLUSIONS

REFERENCES

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