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Interactions supernovae-nuages moléculaires:

Interactions supernovae-nuages moléculaires: effets d'ionisation par le rayonnement cosmique de basse énergie (financement PCHE + PCMI). Thierry Montmerle Laboratoire d’Astrophysique de Grenoble et Institut d’Astrophysique de Paris. TeV astronomy :

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Interactions supernovae-nuages moléculaires:

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  1. Interactions supernovae-nuages moléculaires: effets d'ionisation par le rayonnement cosmique de basse énergie (financement PCHE + PCMI) Thierry Montmerle Laboratoire d’Astrophysique de Grenoble et Institut d’Astrophysique de Paris

  2. TeVastronomy: sources in the galactic plane &evidence for supernovae

  3. Čerenkovtelescopes DE ~ 0.1-100 TeV Dθ ~ 0.1° ~ mol. cloud @ 2-3 kpc

  4. HESS: High EnergyStereoscopic System (Namibia) VERITAS (S. Arizona) Čerenkov TeVtelescopes MAGIC (CanaryIsl.)

  5. HESS galactic plane survey W28 Galactic center Wes 2 Carina arm

  6. 3EG (GeV: Compton GRO) TeV R. Wagner, in Grenier 2008

  7. The g-raysky as seen by Fermi-LAT (Eg ~ 30 MeV-10-300 GeV) 1st yr: 2008-2009 1st catalog (2009): 1451 sources

  8. TeVg-ray sources • Strong concentration along the galactic plane • So far, only a few cross-identificationsbetweenGeV and TeV sources (increasing) • Majority of identified sources connectedwith the end stages of massive star evolution, especiallysupernova remnants (SNRs): • A few compact X-raybinaries (accreting neutron star + companion) • Many “pulsar windnebulae” (“plerion SNR”: Crab-like; g-raysfrom leptons: synchrotron) • Isolatedyoungsupernova remants (Cas A: synchrotron + inverse Compton) • Increasingnumber of oldSNRsinteractingwithmolecularclouds (extendedg-ray sources): CR hadrons at last ? (See COS-B results: “SNOBs”, Montmerle 1979) • Stillmanyunidentified sources (“darkaccelerators”)

  9. IC443 SNR and itsenvironment (d ~ 1.5 kpc, age ~ 3x104yrs) Gem OB1 association IC444 GeV IC443 TeV η Gem pulsar CO OH maser (v ~ 70-100 km/s) Hα

  10. M20 (Trifid) W28 SNR d ~ 2-3 kpc Age ~ 35-150,000 yrs

  11. W28 SNR (Namibia) TeV GeV TeV TeV Aharonian et al. 2009

  12. HESS J1828+020 Radio cm New SNR (jan. 2010): G35.6-0.4 d ~ 10 kpc ? Age ~ 30,000 yr ? CO

  13. 2. Cosmic-rayinducedcloudionization

  14. Whylow-energy (MeV) cosmic rays ? • So far, SN shock interactions with local ISM tested by way of positionalcoincidence, and by enhancedmolecularvelocitycriteria • OH masers (if present) trace moderateshocks (vs < 100 km/s) withinlocalized dense material • p°-decayTeV/GeVemission by molecularclouds good indication of "physical interaction" between local HE CR (> 0.1-10 TeV) and bulkmatter • Other test of "global" interaction: enhancedmolecularcloudionization by the low-energy (<100 MeV) CR component • If successful, gives in addition the local (low-energy) CR spectrumconvolvedwith diffusion coefficient

  15. General idea: assume TeVg-rays come from > TeV protons (p° decay) accelerated by the SNR shock • => Enhancedmolecularcloudionizationcomesfromassociatedlow-energy GCR (> 10 MeV-100 MeV): • Ionizationlosses: stoppingcolumndensity ~ 10 g.cm-2 i.e., ~ a few 1025 cm-2 (e.g., Fatuzzo et al. 2006) => equivalent total irradiated AV ~ 10000 ! • >> N(H2) even for dense molecularcores (x 1022 cm-2 ) • => Efficient confinementnecessary: turbulent magneticfields… True for galacticcosmic rays in general ! • => Measureionizationdegreexe: local CR flux enhancement • Usual value ~ 10-17-10-16 s-1 => for ne ~ 104-105 cm-3, xe ~10-8-10-7 (e.g., Caselli et al. 1998) • => important chemicaleffects (=> H3+ ; H2D+ ; radicals…) • => role in star formation ? (+ magneticfields: ambipolar diffusion) • => Link withGeV/TeV flux

  16. “Ionization test”: ongoing IRAM-30m programs (PI C. Ceccarelli + TM, Dubus, Hily-Blant, Lefloch, + Montpellier/Annecy) • Sample of TeV sources: • SNOB-like sources (IC443, W28, W51C, Cyg OB1) • "Darkaccelerators" (HESS J1841…): extended, but no obviouscounterpart • mm observations: HCO+, DCO+, 12CO, 13CO • CO + H3+ –> HCO+ + H2 • CO + H2D+ –> DCO+ + H2 = 3 DCO+/HCO+ (e.g., Guélin et al. 1977) • xe • + cloud mass from12CO and 13CO measurements

  17. Fermi: Abdo et al. 2009 • W51C SNR • (d ~ 6 kpc, • age ~ 30,000 yrs) • One of the most • luminousg-ray sources • in the Galaxy ! HESS 2010 (prelim.)

  18. W51C, IRAM 30m <xe> x ∼100 H13CO+ DCO+ Hily-Blant, Ceccarelli, Montmerle, Dubus, et al., in prep.

  19. TeV W28 SNR SNR GeV Ep ~ MeV ? Ep > TeV TeV TeV Aharonian et al. 2009

  20. ↪ IRAM 30m proposal Sep. 2010 SF2A-PCHE (22-23/6/10) 21

  21. Conclusions (provisoires…) • Méthode de mesure d’ionisation validée • Cartographie (échantillonnage): nécessite haute résolution pour “bien viser” • Enjeux des observations W28: • Intérêt général: première “carte d’ionisation” d’un nuage moléculaire • Recherche de gradient d’ionisation (amont-aval du choc SNR): lien avec diffusion du RC de basse énergie, et “test” in situ des modèles d’accélération • MAIS: autres sources d’ionisation existent (UV du choc…)

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