X-ray Spectroscopy of Hot Gas in the Milky Way and Beyond
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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)
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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: - PowerPoint PPT Presentation
Transcript of X-ray Spectroscopy of Hot Gas in the Milky Way and Beyond
X-ray Spectroscopy of Hot Gas in the Milky Way and Beyond
Webster CashAstrophysical and Planetary Sciencesand Aerospace Engineering Sciences
and Center for Astrophysics and Space AstronomyUniversity 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)
Diffuse X-ray Background Spectrum
Rosat All-sky Survey
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.
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 vs ~ 1000 km/s
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 SNRvs ~ 500 km/s
Slows down, heats up. Pressure driven from insideConserves energy because there’s no way to lose energy.
vs < 200 km/s
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
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
Vela SNR (and Puppis)
Cygnus Loop
Diffuse X-ray Background Spectrum
From Rocket Shot ofDan McCammon(U. Wisconsin)
Rosat All-sky Survey
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
Spectral Rise Not Explained
From Cash, Malina, and Stern,ApJ (letters), 204, L7, 1976
If we don’t understand the ISM, then
We don’t understand anything about the cycles of matter in the Universe.
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 toDo things differentlyMake mistakes inexpensively
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
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
Payload components• 3.25° FOV + 3 m length =
6.7” opening aperture• Wire grid collimator• Off-plane grating array• Gaseous Electron Multiplier
(GEM) detectors
Wire-grid collimator
Wire-grid collimator
Off-plane grating array
α β
nλ/d
αγ
Off-plane grating array
The world’s “best” detectors
Reflight Step 1: Rebuild
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)
Reflight Step 3: Integration
On the RailShow and Tell with the Commanding General
Ready to Go!
Launch Operations - Blockhouse
Gone!
Helicopter Duty -- 2006Randy, Eric and Travis
Spectrum Nov. 13, 2009
Spectrum is continuum with low percentage narrow lines.That’s interesting!
OVII NVI OVII? NewFe??
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
Is it Bremsstrahlung?
To resolve: Fly again
No
Maybe
What Next?
• Modeling and Theory– Figure out how this works and what it means
• Reflight – December 2011 Vela– Are x-ray remnants
synchrotron driven?
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.
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!
