Star Formation in our Galaxy

1. Star Formation in our Galaxy Dr Andrew Walsh (James Cook University, Australia) Lecture 1 – Introduction to Star Formation Throughout the Galaxy Lecture 2 – Chemistry and Star Formation Lecture 3 – High Mass Star Formation and Masers Lecture 4 – G305.2+0.2: A Case Study and Galactic Plane Surveys

2. Star Formation in our Galaxy • Introduction to Star Formation • Throughout the Galaxy • Why study star formation? • The Galactic ecology • Dark clouds, complexes and giant molecular clouds • The Milky Way at different wavelengths • Young stellar object classes • Disks, jets and outflows • Gravitational collapse • Clustered star formation

3. Why Study Star Formation? Star formation is the process that determines the properties of the major building blocks of the universe: Stars, Planets and Galaxies

4. Why Study Star Formation? The birth of stars is the most poorly understood stage of evolution of stars Star formation is one of the most beautiful processes in the cosmos!

5. McCaughrean et al. 1996

6. The Galactic Ecology Neutron star Molecular Cloud Supernova Triggering SN shocks Cores Black hole HMS winds Outflows High mass Young stellar objects White dwarf Stars Planetary nebula Low mass

7. Cores, Dark clouds, Complexes andGiant Molecular Clouds Giant Molecular Clouds: ~105 solar masses ~50pc

8. Cores, Dark clouds, Complexes andGiant Molecular Clouds Dark Cloud Complexes: ~104 solar masses ~10pc

9. Cores, Dark clouds, Complexes andGiant Molecular Clouds

10. NH3 (1,1) Dark Clouds

11. Optical Near-Infrared Dark Clouds Masses: Between fractions and a few x 10 solar masses Sizes: ~1pc

12. Interstellar Extinction Red light is absorbed by dust less than blue light We can see deeper into dust-enshrouded objects at longer wavelengths. Extinction ~ λ-1.7

13. Optical Near-Infrared 1.2 mm Dust Continuum C18O N2H+ Dark Clouds Masses: Between fractions and a few x 10 solar masses Sizes: ~1pc

14. Properties of Cores, Dark clouds, Complexes and Giant Molecular Clouds Type n Size T Mass [cm-3] [pc] [K] [Msun] Giant Molecular Cloud 102 50 15 105 Dark Cloud Complex 5x102 10 10 104 Individual Dark Cloud 103 2 10 30 Dense low-mass cores 104 0.1 10 10 Dense high-mass cores >105 0.1-1 10-30 100-1000

16. Planck's Black Body

17. Planck's Black Body

18. Wien's Law max = 2.9/T [mm] Examples: The Sun T 6000 K max= 480 nm (optical) Humans T 310 K max= 9.4 mm (MIR) Molecular Clouds T 20 K max= 145 mm (FIR) Cosmic Background T 2.7 K max= 1.1 mm (mm)

20. Spectral Energy Distribution

21. Class 0, I, II and III Young Stellar Objects

22. McCaughrean et al. 1996

24. Herbig 1950, 1951; Haro 1952, 1953 Discovery of outflows Initially thought to be embedded protostars but soon spectra were recognized as caused by shock waves --> jets and outflows

25. Snell et al. 1980 Bachiller et al. 1990 Discovery of outflows • In the mid to late 70th, first CO non-Gaussian line wing emission detected • (Kwan & Scovile 1976). • - Bipolar structures, extremely energetic, often associated with HH objects

26. The prototypical molecular outflow HH211

27. General outflow properties • Jet velocities 100-500 km/s <==> Outflow velocities 10-50 km/s • Estimated dynamical ages between 103 and 105 years • Size between 0.1 and 1 pc • Force provided by stellar radiation too low (middle panel) • --> non-radiative processes necessary! Mass vs. L Force vs. L Outflow rate vs. L Wu et al. 2004, 2005

28. Snell et al. 1980 Spectral Line Profiles • Outflow wings • Infall

29. Spectral Line Profiles • Outflow wings • Infall Rising Tex along line of sight Velocity gradient Line optically thick An additional optically thin line peaks at center

30. Infall Profiles HCO+ (1-0) Optically thick N2H+ (1-0) Optically thin Walsh et al. 2006

31. Infall Profiles Walsh et al. 2006

32. Clustered Star Formation

33. Clustered Star Formation Most stars are formed in clusters (Maybe) ALL High Mass Stars Formed in Clusters

34. Spitzer 3-colour image of NGC 1333 - Courtesy Rob Gutermuth (CfA)

35. Spitzer 3-colour image of NGC 1333 - Courtesy Rob Gutermuth (CfA)

36. Spitzer 3-colour image of NGC 1333 - Courtesy Rob Gutermuth (CfA)

37. Clustered Star Formation Red & Blue = HCO+ (1-0) Greyscale = N2H+ (1-0) + = dust continuum cores Walsh et al. 2007

38. Clustered Star Formation