Erosion, Landfill & Politics in Interstellar Space

1. Erosion, Landfill & Politics in Interstellar Space Alyssa A. Goodman Harvard University Department of Astronomy cfa-www.harvard.edu/~agoodman

2. Erosion,Landfill& Politics

3. At 9 P.M., I hope you have some idea of:What we understand about how stars like the Sun form,and how we came to this understanding

4. "Cores" and Outflows 1 pc = 3 lyr Molecular or Dark Clouds Jets and Disks Solar System Formation What we understand

5. Landfill Magnetohydrodynamic Waves Infall Outflows MHD Turbulence Thermal Erosion Motions What we also understand, but don’t always admit SNe/GRB H II Regions

6. Even thoughit’s nowrightbeforeour eyes

7. How we came to our “modern” understanding • The Politics of Ideas • From admitting stars form, to modern complexity • Politics and Funding • Are the politicians and the public interested?

8. Ideas 1900-2000

9. Ideas: 1900-1948 • Dust, not Holes • c. 1900: Barnard decides “dark” clouds are obscuring material, not “holes” in the distribution of stars • ABCDEFG…  OBAFGKM... • c. 1920s-30s: work of Annie Jump Cannon, Henry Norris Russell, and legions of others lead to decoding stellar structure and evolution from spectra of stars • Protostars? • 1947Bok & Reilly suggest smallest Barnard objects (now called “Bok Globules”) may be protostars

10. Dust, Not Holes

11. Time Showed Barnard was Right! Barnard’s Optical Photograph of Ophiuchus IRAS Satellite Observation, 1983 Remember: Cold (10K) dust glows, like a blackbody, in the far-infrared.

12. Ideas: 1900-1948 • Dust, not Holes • c. 1900: Barnard decides “dark” clouds are obscuring material, not “holes” in the distribution of stars • ABCDEFG…  OBAFGKM... • c. 1920s-30s: work of Annie Jump Cannon, Henry Norris Russell, and legions of others lead to decoding stellar structure and evolution from spectra of stars • Protostars? • 1947 Bok & Reilly suggest smallest Barnard objects (now called “Bok Globules”) may be protostars

13. Post ~1950 HR Diagram Implies finite lifetime for stars need to replenish stellar stock (“Star Formation”!) need to form wide variety of stellar types Stellar Evolution from Spectroscopy: The Hertzprung-Russell Diagram A B C D E F G...

14. Ideas: 1900-1948 • Dust, not Holes • c. 1900: Barnard decides “dark” clouds are obscuring material, not “holes” in the distribution of stars • ABCDEFG…  OBAFGKM... • c. 1920s-30s: work of Annie Jump Cannon, Henry Norris Russell, and legions of others lead to decoding stellar structure and evolution from spectra of stars • Protostars? • 1947Bok & Reilly suggest smallest Barnard objects (now called “Bok Globules”) may be protostars

15. “The Possibility of Star Formation”

16. Bok’s Globules

17. 1948-49 • “[Owing to nuclear physicists good proposal of a ‘big bang’ origin of the Universe some 3 million years ago…] We are indeed forced to conclude that the present variety of stars in the sky is the result of the original method of star formation rather than of any evolutionary process.” • --Lyman Sptitzer, 1948 • “[Even though T Tauri associations could all have similar colors implying young age by coincidence], it is of course, tempting to search for a connection between the T Tauri stars and Bok’s ‘globules,’ but we must admit that at present there is no evidence of any objects intermediate between the two groups.” • --Otto Struve 1949

18. What Happened around 1950? • HR Diagram comes into focus • Globular cluster stars clearly very old (>few Gyr) • T Tauri and other “pre-main-sequence”stars clearly very young (few Myr) • Real admitted needfor star formation • Radio Astronomy finds the Neutral ISM • 1951 Ewen & Purcell detect 21-cm emission from interstellar hydrogen out the window of Harvard’s Jefferson Labs (appreciated as massive amounts of gas, but not concentrated on Bok Globules…) • $ NSF Founded $ (1950) (Keep in mind...NASA Founded 1958)

19. Suddenly, by 1952 “Star Formation” was a Respectable Term & Subject! • “The suggestion that all type I stars have been formed from the interstellar clouds may, perhaps, be taken as a working hypothesis.” • --Schwarzschild, Spitzer & Wildt 1951 • “This, I imagine, is why the oldest members of the stellar system…are so large and populous, for the available material was richer then. As the layer of dust and gas sank toward the galactic plane, stars continued to form. Dust and gas still lie dense in this layer, and stars are still being formed there. • --Cecilia Payne Gaposchkin 1952

20. Tutorial:Velocity from Spectroscopy Observed Spectrum Telescope  Spectrometer 1.5 1.0 Intensity 0.5 0.0 -0.5 All thanks toDoppler 100 150 200 250 300 350 400 "Velocity"

21. Tutorial:Velocity from Spectroscopy Observed Spectrum Telescope  Spectrometer 1.5 1.0 Intensity 0.5 0.0 -0.5 All thanks toDoppler 100 150 200 250 300 350 400 "Velocity"

22. Bok’s Dream: Radio Spectral-line Observations of Interstellar Clouds

23. Bok’s Dream: Radio Spectral-line Observations of Interstellar Clouds Radio Spectral-Line Survey Alves, Lada & Lada 1999

24. And someone had to pay for it... • The 26-m Telescope at Agassiz Station • Harvard, MA • Cost in 1956: $200,000

25. 1957 H I Spectroscopy Telescope  Spectrometer H I Spectrum of the Galaxy M51 from Agassiz Station,Heeschen 1957 All thanks toDoppler

26. Ideas: 1952-1975 • Making Stars from Gas Clouds • 1953 Hoyle’s proposal of hierarchical fragmentation by Jeans instability (Jeans masssmallest mass that will collapse under self-gravity in homogeneous medium of given density & temperature) • 1963 Layzer points out smallest clumps might collide & stick • Protostars? • c. 1952 Herbig & Haro find non-stellar bright knots associated with “dark clouds” (HH Objects) • Molecules in Space, Molecular Clouds • CH absorption (1940); OH absorption (1963)emission(1965);CO emission (1970) • Emission associated with & dark clouds Bok Globules

27. Star Formation c. 1953 Fragments Collapse Under Gravity into “Protostars” time~105 years Global Instability (e.g. Jeans) Fragments Cloud (hierarchically) time~106 years Hoyle 1953

28. Star Formation in 1953 A Group of Young “Zero-Age Main Sequence” Stars is Born

29. HH Objects

30. “Giant” Herbig-Haro Flows:PV Ceph 1 pc Reipurth, Bally & Devine 1997

31. Velocity as a "Fourth" Dimension Loss of 1 dimension No loss of information

32. “Integrated Intensity Map” Region of Radio Spectral-Line Survey Alves, Lada & Lada 1999

33. Ideas: 1975-1985 • More Collapse and Fragmentation Scenarios • 1970s-now Resurgence of “Triggered” Star Formation Ideas (Erosion, Landfill) • Triggers: SNe, H II Regions, cloud-cloud collisions, shocks, star formation itself • Protostars? • 1970s-now Infrared detectors unveil the youngest stars • 1975 KAO begins flights; 1983 IRAS Satellite • Oops! Bipolar Outflows (More erosion & landfill?) • 1980 Unpredicted discovery of bipolar flows associated with HH objects

34. "Cores" and Outflows 1 pc = 3 lyr Molecular or Dark Clouds Jets and Disks Solar System Formation The Story, c. 1990

35. 100 mm Dust Emission in Cassiopeia Tóth et al. 1995 Molecular Clouds "Created" by Supernovae

36. Star Formation Triggered by A Galaxy Collision HST Image of the Antennae, Whitmore et al.

37. Magnetohydrodynamic Waves Infall Outflows MHD Turbulence Thermal Motions The Star-FormingInterstellar Medium SNe/GRB H II Regions

38. Ideas: 1985-now • Magnetic Fields • 1937 Alfvén proposes Galactic B; 1949-1951 appreciation of polarization by magnetically-aligned dust; 1968 1st Zeeman observations; 1988 The bandwagon drives off... • Protostellar Disks • 1980s,90s Interferometer Disks; 1990s HST Disks • *Clumping, Turbulence, Clustering and the IMF • c. 1990- Big Maps, “Big Pictures” • *Environmental Influences • c. 1990s HST reminds us about Erosion & Landfill

39. Do Magnetic Fields Explain Everything? (line width)~(size)1/2 (density)~(size)-1 Curves assume M=K=G (Myers & Goodman 1988)

40. Erosion

43. My Ideas

44. The Spectral Correlation Function Figure from Falgarone et al. 1994 Simulation

45. [ ] T / 10 K b = [ ] 2 -3 [ ] n B m / 100 cm / 1 . 4 G H 2 Strong vs. Weak B-Field b=0.01 b=1 • Driven Turbulence; M K; no gravity • Colors: log density • Computational volume: 2563 • Dark blue lines: B-field • Red : isosurface of passive contaminant after saturation Stone, Gammie & Ostriker 1999

46. 1950 1960 1970 1980 1990 2000 8 10 4 10 7 10 N 6 channels, 10 channels 3 10 *N N 5 10 channels pixels S/N in 1 hour, 2 10 4 10 (S/N)*N N 3 10 1 N 10 pixels pixels 2 10 0 10 1950 1960 1970 1980 1990 2000 Year The SuperstoreLearning More from “Too Much” Data Product S/N

47. Measures similarity of neighboring spectra within a specified “beam” size lag & scaling adjustable signal-to-noise accounted for How the SCF Works See: Rosolowsky, Goodman, Wilner & Williams 1999; Padoan, Rosolowsky & Goodman 1999.

48. 1.0 0.8 0.6 Increasing Similarity of ALL Spectra in Map 0.4 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Which one of these is not like the others? Increasing Similarity of Spectra to Neighbors Rosette C 18O Rosette 13CO Change in Mean SCF with Randomization Rosette 13CO Peaks SNR HCl2 C 18O H I Survey L134A 13CO(1-0) Rosette C 18O Peaks Pol. 13CO(1-0) L1512 12CO(2-1) G,O,S HCl2 C 18O Peaks L134A 12CO(2-1). MacLow et al. HLC Falgarone et al. Mean SCF Value

49. “Giant” Herbig-Haro Flows:PV Ceph 1 pc Reipurth, Bally & Devine 1997

50. A New Proposal: Episodic ejections from precessing or wobbling moving source Required motion of 0.25 pc (e.g. 2 km s-1 for 125,000 yr)