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Interaction of the SNR with The Surrounding Medium

Interaction of the SNR with The Surrounding Medium. 1. The Interstellar Medium (ISM) 2. Radio Telescopes 3. The Supernova Remnants (SNRs) & CO. Useful Readings. Burton, W.B. et al. 1991, “The Galactic Interstellar Medium” Spitzer, L. 1978, “Physical Processes In The Interstellar Medium”

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Interaction of the SNR with The Surrounding Medium

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  1. Interaction of the SNR with The Surrounding Medium • 1. The Interstellar Medium (ISM) • 2. Radio Telescopes • 3. The Supernova Remnants (SNRs) & CO

  2. Useful Readings • Burton, W.B. et al. 1991, “The Galactic Interstellar Medium” • Spitzer, L. 1978, “Physical Processes In The Interstellar Medium” • Dickey, J.M. & Lockman, F.J. 1990, ARA&A

  3. The Four Components of the Interstellar Medium

  4. Star HII HII+dust HI+dust+molecules

  5. How do we detect the ISM? Many tracers throughout the E-M spectrum • Spectral emission lines • e.g. H (optical), HI (radio), CO (millimeters), recombination lines (H109 in the radio) • Spectral absorption lines • e.g. HI, Ca, Na, Fe • Thermal continuum emission • e.g. PAH emission (12m), HII regions (radio, infrared, optical, millimeter, …), hot, diffuse plasma (Xray) • Nonthermal continuum emission • e.g. synchrotron emission from the magnetoionic medium • Absorption and Scattering • e.g. dust grains (Xray, UV, optical) • Reflection • e.g. dust grains (optical light)

  6. Spectral Line Sources • Neutral hydrogen (H I ) spin-flip transition • Recombination lines (between high-lying atomic states) • Molecular lines (CO, OH, etc.)

  7. Observing Neutral Hydrogen:The 21-cm (radio) line Neutral hydrogen (HI) can be traced by observing this radio emission - naturally narrow width of this line makes it an ideal diagnostic of interstellar hydrogen because the strength of the line depends on the density and temperature of the hydrogen gas. The observation of the 21cm line of hydrogen marked the birth of spectral-line radio astronomy.

  8. Observations of the 21-cm Line G a l a c t i c p l a n e All-sky map of emission in the 21-cm line

  9. Observations of the 21-cm Line HI clouds moving towards Earth HI clouds moving away from Earth Individual HI clouds with different radial velocities resolved (from redshift/blueshift of line)

  10. HI Shells and Supernova Remnants: SNR G327.7+0.4 • The HI around a supernova remnant (SNR) is also modified by the remnant • HI ring around SNR G327.7+0.4

  11. The Most Easily Observed Molecules in Space • CO = Carbon Monoxide Radio emission • OH = Hydroxyl Radio emission. The Most Common Molecule in Space: • H2 = Molecular Hydrogen  can be detected by far ultraviolet absorption and emission: - very difficult to observe. But: Where there’s H2, there’s also CO - cloud may contain only 1 CO per 10,000 H2, - enough to see Use CO as a tracer for H2 in the ISM.

  12. CO emission lines show molecular cloud complexes. • Stars apparently form in these dense regions.

  13. BBU CO GRS CGPS HI A common view of the ISM?

  14. Tracing the ISM Life Cycle Supernova Explosions Planetary Nebulae Hot Gas: Bubbles, shells, & chimneys • Fluorescence of an H envelope NII, OII, Hb, etc. • Far-UV and Xray • continuum, • Ha, OVI spectral lines Diffuse WNM Stellar Winds HII regions • HI emission Thermal continuum • HI absorption Cold atomic clouds • H2, CO and other molecular lines • Masers Dredge up spectral lines Metals in the ISM Molecular Clouds Nucleosynthesis Star Formation

  15. Electromagnetic Radiation Wavelength Radio Detection techniques developed from meter-wave to submillimeter-wave: = 1 meter   = 300 MHz = 1 mm   = 300 GHz

  16. What looks dark in one wavelength may look bright in another.

  17. Light Pollution Earth at Night Credit: C. Mayhew & R. Simmon (NASA/GSFC), NOAA/ NGDC, DMSP Digital Archive

  18. What do Radio Astronomers measure? • Luminosity of a source: L = dE/dt erg/s • Flux of a source at distance R: S = L/4R2 erg/s/cm2 • Flux measures how bright a star is. In optical astronomy, this is measured in magnitudes, a logarithmic measure of flux. • Intensity: If a source is extended, its surface brightness varies across its extent. The surface brightness is the intensity, the amount of flux that originates from unit solid angle of the source: I = dS/d erg/s/cm2/steradian

  19. |u ()|2 |u ()|2

  20. Radiometer Equation • For an unresolved source, the detection sensitivity of a radio telescope is determined by the effective area of the telescope and the “noisiness” of the receiver • For an unresolved source of a given flux, S, the expected antenna temperature is given by kTA = ½ Ae,maxS • The minimum detectable TA is given by TA = Ts/(B) where Ts is the system temperature of the receiver, B is the bandwidth and  is the integration time, and  is of order unity depending on the details of the system. The system temperature measures the noise power of the receiver (Ps = BkTs). In Radio Astronomy,detection is typically receiver noise dominated.

  21. How do radio telescopes work?

  22. Sources of Radio Emission 1. Blackbody (thermal) 2. Continuum sources 3. Spectral line sources

  23. Blackbody Sources • Peak in cm-wave radio requires very low temperature: lmT = 0.2898 cm K • Cosmic Microwave Background is about the only relevant blackbody source • Ignored in most work – essentially constant source of static (same in all directions) and much weaker than static produced by instrumentation itself

  24. Continuum Sources • Due to relativistic electrons: Synchrotron radiation Bremsstrahlung • Quasars, Active Galactic Nuclei, Pulsars, Supernova Remnants, etc. • Used by ALFALFA for calibration

  25. H I spectral line from galaxy shifted by expansion of universe (“recession velocity”) and broadened by rotation Frequency

  26. What is Resolution?

  27. Type Ia Type II • Disruption of a binary system: • SNR • Core-Collapse: • Neutron Star or a black hole • SNR SN types

  28. SN 1987A discovered by I. Shelton 02/24/87 (originally from Winnipeg!) Why SNe? Neutrinos! (a SN explosion releases 1053 ergs, erg=10-7 J)

  29. Tracking the elements we are made of! Why Study SNRs ? • Interstellar Medium : Dynamics, Energetics, Magnetic Field • Nearby Laboratory to study physics in extreme conditions: Neutron Stars & Black Holes (QED, General Relativity, Gravitational Waves)

  30. Survey of Molecular Clouds around Galactic SNRs Yamamoto, F.; Hasegawa, T.; Sawada, T.; Sugimoto, M.; Naitoh, S.; Handa, T.; Sofue, Y. IAU 8th Asian-Pacific Regional Meeting

  31. Survey of Molecular Clouds around Galactic SNRs

  32. The Environment of Tycho: Possible Interaction with the Molecular Cloud Lee, Jae-Joon; Koo, Bon-Chul; Tatematsu, Keni'chi 2004ApJ...605L.113L Type Ia, 1572, d=2.3 Kpc

  33. Thank you for your attention

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