X-ray Spectroscopy of Hot Gas in the Milky Way and Beyond

1. X-ray Spectroscopy of Hot Gas in the Milky Way and Beyond Webster Cash Astrophysical and Planetary Sciences and Aerospace Engineering Sciences and Center for Astrophysics and Space Astronomy University of Colorado Much of the work done by: Randy McEntaffer (now Asst. Prof. Univ of Iowa) Phil Oakley (now at MIT) Ben Zeiger (bears the brunt of the next flight)

2. Diffuse X-ray Background Spectrum Rosat All-sky Survey

3. Theory of ISM • Field, Goldsmith and Habing had Cosmic Ray heating in 1969 • McKee and Ostriker had SNR heating in 1977 • And there we still are. Somehow this became orthodoxy.

4. vs ~ 1000 km/s SNR evolution • Theory (uniform medium) • 4 phases • Free expansion • Lasts ~100years • Adiabatic (Sedov) • MISM > Mejecta • Radiative • Thermal equilibrium • Merge Into ISM • Runs into other SNR

5. SNR evolution • Theory (uniform medium) • 4 phases • Free expansion • Adiabatic (Sedov) • MISM > Mejecta • Lasts thousands of years • Radiative • Thermal equilibrium • Merge Into ISM • Runs into other SNR vs ~ 500 km/s Slows down, heats up. Pressure driven from inside Conserves energy because there’s no way to lose energy.

6. SNR evolution • Theory (uniform medium) • 4 phases • Free expansion • Adiabatic (Sedov) • MISM > Mejecta • Radiative • Thermal equilibrium • Loses energy to x-ray radiation • Lasts 100’s of thousands of years • Merge Into ISM • Runs into other SNR vs < 200 km/s

7. SNR evolution • Theory (uniform medium) • 4 phases • Free expansion • Adiabatic (Sedov) • MISM > Mejecta • Radiative • Thermal equilibrium • Merge into ISM • Runs into other SNR • Becomes part of ISM

8. Vela SNR (and Puppis)

9. Cygnus Loop

10. Diffuse X-ray Background Spectrum Rosat All-sky Survey From Rocket Shot of Dan McCammon (U. Wisconsin)

11. But There Are Problems • Nicely summarized by Cox in ARAA 2005 • 25% Variable • Charge Exchange with Solar Wind • O VI Underabundant by a factor of 100 • Soft X-ray Background too faint by x10 • B fields out of pressure equilibrium

12. Spectral Rise Not Explained From Cash, Malina, and Stern, ApJ (letters), 204, L7, 1976

13. If we don’t understand the ISM, then We don’t understand anything about the cycles of matter in the Universe.

14. Now Let’s Get to the Rockets! “Insanity is doing the same thing over and over again and expecting different results.” Albert Einstein “An expert is a man who has made all the mistakes which can be made, in a narrow field.” Neils Bohr Rockets allow us to Do things differently Make mistakes inexpensively

15. Project Overview • Proposed in April 2003 • Awarded funding in fall 2003 • Raytrace, design, fabrication 2004-2005 • Calibrations and final assembly 2006 • Integration at Wallops Flight Facility Launched • November 20th, 2006 • November 13th, 2009 White Sands Missile Range, New Mexico

16. Design overview • Known as EXOS • Extended X-ray Off-plane Spectrograph • FOV and payload length determine design • Payload length = 3 m (longest payload ever flown) • 3.25° × 3.25° FOV • 1 m to form beam, 2 m to disperse it

17. Payload components • 3.25° FOV + 3 m length = 6.7” opening aperture • Wire grid collimator • Off-plane grating array • Gaseous Electron Multiplier (GEM) detectors

18. Wire-grid collimator

19. Wire-grid collimator

20. nλ/d β α γ α Off-plane grating array

21. Off-plane grating array

22. The world’s “best” detectors

23. Reflight Step 1: Rebuild

24. Reflight Step 2 • Make the damn thing work • No glory, no pictures, just Phil Oakley working his behind off for a year. • Lots of things break, fix them, something else breaks • Eventually everything that can go wrong has.(the upside of Murphy’s Law)

25. Reflight Step 3: Integration

26. On the RailShow and Tell with the Commanding General

27. Ready to Go!

28. Launch Operations - Blockhouse

29. Gone!

30. Helicopter Duty -- 2006 Randy, Eric and Travis

31. Spectrum Nov. 13, 2009 OVII NVI OVII? New Fe?? Spectrum is continuum with low percentage narrow lines. That’s interesting!

33. Radiation Mechanisms • Blackbody • Optically thick body in thermal equilibrium • Bremsstrahlung (means “braking radiation”) • Optically Thin Body • Photons result from collisions (and consequent deceleration) of charged particles (ions and electrons) • Synchrotron • Relativistic electrons spiraling in a magnetic field • Protons don’t accelerate as fast – not much emission • Non-relativistic emission called Cyclotron Radiation

34. Is it Bremsstrahlung? To resolve: Fly again No Maybe

35. What Next? • Modeling and Theory • Figure out how this works and what it means • Reflight – December 2011 Vela • Are x-ray remnants synchrotron driven?

36. Other Uses • Comets • Surprising Discovery in 1990’s of x-rays fromcomets • Charge Exchange at Heliopause • 25% of Soft X-rays vary with solar wind • Elsewhere? • Earth Atmosphere? • Most sensitive diffuse spectrograph ever, might see new features.

37. Summary • Built EXOS • Central Role Played by Students • Obtained Spectrum of Cygnus Loop • Wasn’t what was expected • Possible Indication of Greater Role for High Energy Particles • SNR seen as birthplace of cosmic rays • Reassess Energy Balance of ISM • Needs More Flights!