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Supernova Remnants in the ChASeM33 X-ray Survey of M33

Supernova Remnants in the ChASeM33 X-ray Survey of M33. Knox S. Long, William P. Blair, P. Frank Winkler, and the ChASeM33 team. Background . X-ray H  [S II] v.

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Supernova Remnants in the ChASeM33 X-ray Survey of M33

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  1. Supernova Remnants in the ChASeM33 X-ray Survey of M33 Knox S. Long, William P. Blair, P. Frank Winkler, and the ChASeM33 team

  2. Background X-ray H [S II] v • SNRs in nearby galaxies identified primarily from [SII]:Ha ratios > 0.4. HII regions ~ 0.1 • Before this work, ~100 optical SNRs in M33 • 98 from [S II]: Ha imagery (Gordon et al 1998) • 53 have radio fluxes (Gordon et al 1999) • Before Chandra and XMM, few SNRs detected in X-rays outside Galaxy and MCs. In M33: • 10 counterparts with ROSAT (Long et al.1996) • 22 with Chandra (Ghavamian et al. 2005) • 12 (+13 candidates) with XMM (Misanovic et al 2006)

  3. ChASeM33 • Basics • ACIS-I • 7 bore sight pointings totaling 1.4Ms • Minimum depth of ~ 200 ksec, 400 ksec typical. • Highlights • 662 point sources • Two eclipsing binaries • Unusual giant HII region IC 133 dominated by non-thermal emission • Sensitive to SNRs • At M33, 20 pc = 5” • LX > ~2 1034 erg s-1.”

  4. H images of Southern Arm

  5. Optical SNRs in M33’s southern spiral arm on Chandra image

  6. Imaging of Bright SNRs

  7. Spectroscopy of Bright SNRs • 7SNRs with enough counts for spectral analysis • M33 SNR 21 is ISM- dominated expanding into dense molecular cloud (Gaetz et al 2007) • M33 SNR 31 has a spectrum resembling the core-collapse object E0102 in the SMC

  8. Finding X-ray SNRs X-ray H [S II] v • Approach – Use optical SNRs as the starting point • 137 optical SNR and SNR candidates after our re-inspection of the available interference imaging (LGGS and new Schmidt images • Want accurate fluxes, but the basic difficulties are: • Many point sources need to be excluded from background regions • Chandra point source response function varies across field • Solution - Use Patrick Broos’ AcisExtract S/W • The Procedure • Pass 1 - Carry out standard extraction treating all as point sources • Expanding point source region files of SNRs to account for SNR size • Pass 2 – Re-process the SNRs only • Check and repeat Pass 2 as necessary

  9. Finding X-ray SNRs - Results • 82 of 137 SNRs > 2  • 61 (of 96) GKL SNRs • 21 other SNR candidates also detected • Chance probability low

  10. SNRs have soft X-ray spectra S=0.35-1.2 keV, M=1.2-2.6 keV; Total=0.35-8 keV

  11. Luminosity Function

  12. Mostly Middle-Aged SNRs Sample, >2  , >3  • Median diameters • All= 44 pc • Detected = 38 (32) pc; • Undetected = 54 pc

  13. Simple Interpretation Middle age SNRs dominate detections (and sample) Lx at a single diameter is highly variable Very large objects are always faint 60%is detected; 40% is not Lx ~  n2 R3  (0.35-2 keV) ~ constant for kT>0.3 keV  drops rapidly for kT<0.3 keV T inversely proportional to M M(Mo) = 83 T(keV)-1 E51 Implications Small diameter objects are faint Large diameter( Rmax ~ n1/3) are faint Lx of intermediate diameter objects strongly dependent on density (n2) Just the Facts It’s the environment, stupid!

  14. Would your favorite SNR have been detected? Radio: No objects as bright as Crab; one possible PWN, coincident with slightly extended, non-thermal radio source X-ray: No bright sources (>4 1035 erg s-1) that are thermal except stars or known SNRs • At the distance of M33, we should have detected • Most of the bright SNRs in the Galaxy and Magellanic Clouds • Most historical SNe - the Crab Nebula, Tycho, Cas A, & Kepler

  15. Are X-ray properties correlated with other properties? • Extreme X-ray SNRs are extreme in most respects • High Lx objects tend to be high LH objects • High Lx objects are generally to be radio detected • Converse is often not true • High LH objects often not X-ray detected • High radio flux objects often not X-ray detected

  16. The M33 SNR sample

  17. Summary • ChASeM33 enabled the sensitive study of SNRs in M33 we had hoped • Individual SNRs can be studied • The sample of SNRs brighter than LX ~4 1035 ergs s-1 is complete • X-ray SNRs in M33 with LX> 2 1034 ergs s-1 now total 82 • Given that many SNRs are near the luminosity limit, a factor of 2 or 3 in sensitivity would likely reveal the rest. • There are large variations of properties at a given size. • Need to understand local environment to extract class properties of SNRs

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