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A Universal Luminosity Function for Radio Supernova Remnants

A Universal Luminosity Function for Radio Supernova Remnants. Laura Chomiuk University of Wisconsin--Madison. Are SNRs fundamentally the same across galaxies?. Lacey & Duric (2001). The brightest SNR in M33 is ~10 times less luminous than the brightest SNR in NGC 6946.

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A Universal Luminosity Function for Radio Supernova Remnants

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  1. A Universal Luminosity Function for Radio Supernova Remnants Laura Chomiuk University of Wisconsin--Madison

  2. Are SNRs fundamentally the same across galaxies? Lacey & Duric (2001) The brightest SNR in M33 is ~10 times less luminous than the brightest SNR in NGC 6946.

  3. Radio SNRs in Other Galaxies SNR H II region Background source NGC 4449 20 cm 8 SNRs found in NGC 4449 by Chomiuk & Wilcots (2009). NGC 4449 H

  4. IC 10 LMC SMC M 33 NGC 1569 NGC 300 NGC 4214 NGC 2366 M 82 M 81 NGC 7793 NGC 253 NGC 4449 M 83 NGC 4736 NGC 6946 NGC 4258 Arp 220 M 51 SNRs in 19 Nearby Galaxies

  5. Cumulative Luminosity Functions

  6. Composite SNR Luminosity Function  = -2.07  0.07

  7. Arp 220: outlier? LF scaling factor (assuming = -2.13) Approximately linear relation:

  8. Therefore, the SNR LF can be described as: We can rewrite dN/dL as: dN/dt is the production rate of SNRs,  SFR. dL/dt describes the luminosity evolution of SNRs.

  9. 3 cm-3 0.3 cm-3 0.003 cm-3 Some Approximations • Radio SNRs are in the adiabatic phase. • In the adiabatic phase, the CR energy does not depend on time or ISM density. • ECR/ESN constant. From Berezhko & Volk (2004)

  10. Therefore, it is the magnetic field that determines dL/dt. Standard prescription for magnetic field amplification: Making these simplifications, we find an expression for the time evolution of synchrotron luminosity: And for the luminosity function: • = -2.1 A very good fit to the data!

  11. Best fit to data Prediction for statistical sampling from Monte Carlo simulations The Lmax--SFR relation Just a statistical sampling effect?

  12. Cas A on the Lmax--SFR relation Only a 3% probability that a galaxy with Lmax LCas A has a SFR > 2 M/year

  13. Conclusions • The SNR LF is remarkably similar across galaxies. It is consistent with a power law of constant index and scaling  SFR. • The SNR LF is well fit with models of diffusive shock acceleration + magnetic field amplification, given a few simplifying assumptions. • Galaxies with higher SFRs host more luminous SNRs; this can be completely explained by statistical sampling effects. • The luminosity of Cas A implies that current estimates of the Milky Way SFR may be too high.

  14. Model the SNR LFs as power laws The four “best” galaxies (NSNR>20) all have similar best-fit : weighted mean  = -2.26  0.10

  15. Is there a dependence on ISM density? Line marks theoretical prediction: A/SFR  00.5

  16. There are claims that B2 0 vs3 instead of  0 vs2. This would predict dL/dN  L-1.74. Decidedly not in agreement with the SNR LF data. From Vink (2004).

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