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Fermi-LAT Study of Cosmic-rays/Diffuse Gamma-rays and Implications on Particle Physics

Fermi-LAT Study of Cosmic-rays/Diffuse Gamma-rays and Implications on Particle Physics. Mar. 7, 2011 @ Kyoto Univ. Tsunefumi Mizuno (Hiroshima Univ.) On behalf of the Fermi-LAT collaboration. Fermi 衛星による広がったガンマ線・ 宇宙線電子の観測と基礎物理への制限. 2011 年 3 月 7 日 @ 京都大学基礎物理研究所 水野　恒史 ( 広島大学理学部 )

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Fermi-LAT Study of Cosmic-rays/Diffuse Gamma-rays and Implications on Particle Physics

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  1. Fermi-LAT Study of Cosmic-rays/Diffuse Gamma-rays and Implications on Particle Physics Mar. 7, 2011 @ Kyoto Univ. Tsunefumi Mizuno (Hiroshima Univ.) On behalf of the Fermi-LAT collaboration

  2. Fermi衛星による広がったガンマ線・宇宙線電子の観測と基礎物理への制限Fermi衛星による広がったガンマ線・宇宙線電子の観測と基礎物理への制限 2011年3月7日 @ 京都大学基礎物理研究所 水野　恒史 (広島大学理学部) On behalf of the Fermi-LAT collaboration

  3. Introduction Fermi LAT instrumentation Galactic Diffuse Gamma-rays Behind the diffuse gs: EGB and DM search Cosmic-ray Electrons Outline

  4. Gamma-ray Sky • GeV gamma-ray sky = Point sources + Diffuse Gamma-rays >=80% of g-rays Geminga Vela Crab 3c454.3 Fermi-LAT 1 year all-sky map

  5. What makes Diffuse g-rays? InterStellarMedium InterStellarRadiation Field • Diffuse Gamma-rays = Cosmic-rays x (ISM, ISRF) Galactic plane nearby gas in high latitude Planck microwave map = ISM gas

  6. Gamma-ray Sky phys. processes are well understood • GeV gamma-ray sky ~ Diffuse Gamma-rays = CRs x (ISM, ISRF) Fermi-LAT 1 year all-sky map

  7. Why are they important? • Diffuse Gamma-rays are • “probe” to study Galactic CRs and ISM • “foreground” to study exotic physics, e.g., • signal from dark matter (DM) • extragalactic g-ray background (EGB) annihilation or decay new source classes or DM signal Fermi-LAT 1 year all-sky map

  8. Example: GeV Excess (EGRET Era) • EGRET (1991-2000) reported excess emission when compared with a standard diffuse g-ray model • variety of explanations including DM signal E2 x Flux G ~ 2.7 (CR protons) excess 0.1 1 10 GeV Hunter+97

  9. Example: GeV Excess (Fermi Era) • EGRET GeV excess not confirmed. • However, Fermi data allow us investigating more subtle “anomalies” (and detailed study of CRs/ISM) E2 x Flux EGRET Fermi-LAT Abdo+09 PRL 103, 251101 G ~ 2.7 0.1 1 10 GeV

  10. Fermi-LAT as Electron Detector • Fermi-LAT reported a harder CR e- + e+ spectrum compared with a conventional model highest statistics: 4.5 M events (6 months) E3 x Flux Fermi Data (2009) Abdo+09 PRL 102, 181101 10 100 1000 GeV

  11. Fermi-LAT as Electron Detector • Fermi-LAT reported a harder CR e- + e+ spectrum compared with a conventional model • Lots of interpretations (astrophysical and exotic) Fermi e- + e+ PAMELA e+ ratio + = DM? Nearby objects?

  12. Fermi-LAT as Electron Detector • Fermi-LAT reported a harder CR e- + e+ spectrum compared with a conventional model • Lots of interpretations (astrophysical and exotic) … and the paper is highly cited 2009 Jan. – 2010 Sep.

  13. Fermi-LAT Instruments

  14. Fermi Launch • Launched on June 11, 2008 • Science Operation on Aug 4, 2008 • Orbit: 565 km, 26.5o (low BG) 5-yr mission (10-yr goal) Fermi=LAT+GBM Cape Canaveral Air Station @ Florida

  15. Fermi-LAT Collaboration France Italy Japan Sweden US • Hiroshima Univ. • Tokyo Tech • ISAS/JAXA • Waseda Univ. • Tokyo Univ. • Nagoya Univ. • Aoyama Gakuin Univ. ~400 members

  16. Large Area Telescope • Pair-conversion type g-ray telescope 20 MeV- 300 GeV • Tracker: Si-strip detectors • direction measurement ~200 um pitch => high precision tracking • ACD: plastic scintillators • BG rejection segmented tiles => prevent self-veto • Calorimeter: CsI scintillators • Energy measurement hodoscopic crystals => shower profile

  17. Large Area Telescope • Pair-conversion type g-ray telescope • Tracker: Si-strip detectors • direction measurement • Key-element of LAT, developed by HPK and Hiroshima Univ. • Low-noise (~2.5nA/cm2) • High-quality (dead strip: <0.01%) • ~106 channels in total SSD

  18. Performance of the LAT • Large FOV (2.4 sr) • Large Aeff (>=8000 cm2 in 1-100 GeV) • Good PSF (0.6 deg@ 1GeV) sensitivity to point sources EGRET 3rd Catalog 271 sources Fermi-LAT 1st year catalog 1451 sources Atwood+09

  19. Science Breakthroughs of 2009 • Fermi is recognized as one of the top science breakthroughs Science, December 2009 Discovery of 16 new pulsars

  20. GeV Gamma-ray Sky by LAT • and provides us with high-quality data! • g-ray sources, diffuse g-rays and more >100 publications as of Feb. 2011 Fermi-LAT 1 year all-sky map

  21. Diffuse g-rays as probe of CRs and ISM

  22. GeV “Non” Excess • Fermi does not confirm EGRET GeV excess local (<= 1 kpc from the sun) Diffuse Gamma-rays E2 x Flux EGRET Fermi-LAT Abdo+09, PRL 103, 251101 (CA: Johannesson, Porter, Strong) 0.1 1 10 GeV

  23. GeV “Non” Excess • Fermi does not confirm EGRET GeV excess Instead, data is compatible with a standard model Gamma = CR x (ISM, ISRF) E2 x Flux EGRET Fermi-LAT G ~ 2.7 Abdo+09 (CA: Johannesson, Porter, Strong) 0.1 1 10 GeV

  24. Diffuse gs in the Outer Galaxy • Any unexpected in diffuse gs? • Yes. New information on CRs and ISM The outer Galaxy (from outside) sun L=90deg L=270deg II quad III quad L=180deg

  25. Diffuse gs in the Outer Galaxy • Any unexpected in diffuse gs? • Yes. New information on CRs and ISM The outer Galaxy (from the Fermi-LAT) Abdo+10, ApJ 710, 133 Ackermann+11, ApJ 726, 81 GC anticenter

  26. ISM not visible by Standard Tracers • Fermi revealed ISM gas not traced by radio surveys Residual when fitted by N(HI)+CO excess gammas = residual gas Ackermann+11, ApJ 726, 81 (CA: Grenier, Mizuno, Tibaldo)

  27. ISM not visible by Standard Tracers • Fermi revealed ISM gas not traced by radio surveys • confirming an earlier claim based on EGRET study (Grenier+05) Residual when fitted by N(HI)+CO Residual gas inferred by dust Ackermann+11, ApJ 726, 81 (CA: Grenier, Mizuno, Tibaldo)

  28. More CRs than Expected • Fermi detected more gs (more CRs) than a prediction based on SNR distribution and standard CR halo Gamma-ray intensity Sun Ackermann+11 ApJ 726, 81 (CA: Grenier, Mizuno, Tibaldo) Distance from GC (kpc)

  29. More CRs than Expected • Fermi detected more gs (more CRs) than a prediction based on SNR distribution and standard CR halo • More CR sources or larger CR halo Gamma-ray intensity Sun Ackermann+11 ApJ 726, 81 (CA: Grenier, Mizuno, Tibaldo) Distance from GC (kpc)

  30. Remarks on Diffuse gs • g-rays = CR x (ISM, ISRF) • “dark gas” is confirmed (more ISM gas) • More CRs than expected in outer Galaxy • Improvement of diffuse g-ray model Basis to search for anomalies (in spectral and spatial distribution)

  31. Behind Diffuse g-rays: Study of EGB and DM search

  32. Extragalactic Gamma-ray Background • “Cosmic” Extragalactic Gamma-ray Background (EGB) has been known since 1970s G ~ 2.1 E2 x Flux CXB (resolved into AGNs) GeV background (EGRET) Sreekumar+98 keVMeVGeV

  33. Why is EGB Important? • The EGB may encrypt the signature of the most powerful processes in astrophysics Star forming galaxies Point sources or diffuse 73% Dark Energy 4% Atoms 23%Dark Matter Blazars contribute 20-100% of the EGB Annihilation of Cosmological Dark Matter Particles accelerated in Intergalactic shocks Markevitch+05

  34. The Fermi EGB LAT sky • Fermi data + improved diffuse model • new EGB spectrum in 0.2-100 GeV • carefully examine systematic uncertainty = gal. diffuse Single PL, softer than EGRET result + point sources G ~ 2.4 + Instrumental BG Abdo+10, PRL 104, 101101  0.1 1 GeV 10 100 (CA: Ackermann, Porter, Sellerholm) +”EGB”

  35. Blazar Contribution • Blazars account fora minimum of 16+-2% • Even if we extrapolate and integrate logN-logS to zero, contribution is still <40% logN-logS: Most of un-associated sources are likely to be blazars Fermi EGB vs. source contribution flatter in F<=6x10-8 0.1 1 GeV 10 100 Abdo+10, ApJ 720, 435 (CA: Ajello, Tramacere)

  36. Blazar Contribution • Blazars account for a maximum of 40% of EGB • g-ray “Fog” by Mysterious Dragons • star-forming galaxies, normal AGNs or truly diffuse? Fermi EGB vs. source contribution 0.1 1 GeV 10 100 Abdo+10, ApJ 720, 435 (CA: Ajello, Tramacere)

  37. Limits on DM Annihilation • Limits on DM by imposing the EGB is not violated 1.2 TeVm+m- 1.2x10-23 cm3/s 180 GeVgg 2.5x10-26 cm3/s 200 GeV bb 5x10-25 cm3/s 0.1 1 10 100 GeV Abdo+10, JCAP 4, 14 (CA: Conrad, Gustafsson, Sellerholm, Zaharijas)

  38. Limits on DM Annihilation • Limits on DM by imposing the EGB is not violated w/o astrophysical sources m+/m- w/ astrophysical sources 10-22 <sv> (cm3/s) Fermi PAMELA 10-25 • 1000GeV • WIMP mass Abdo+10, JCAP 4, 14 (CA: Conrad, Gustafsson, Sellerholm, Zaharijas)

  39. Limits on DM Annihilation • Limits on DM by imposing the EGB is not violated • already excluded some models, e.g., m+/m- channel favored by PAMELA/Fermi e-/e+ w/o astrophysical sources m+/m- w/ astrophysical sources 10-22 <sv> (cm3/s) Fermi fit 10-25 • 1000GeV • WIMP mass Abdo+10, JCAP 4, 14 (CA: Conrad, Gustafsson, Sellerholm, Zaharijas)

  40. Other Constraints on DM • Dwarf Spheroidal Galaxies are DM dominated • small BG (gas, star-forming activity) No detection give constraints on some models, particularly m+/m- channel m+/m- UL with CMB IC dwarfs Diffusion coeff. dwarfs Abdo+10, ApJ 712, 147 (CA: Cohen-Tanugi, Farnier, Nuss, Profumo, Jeltema)

  41. Remarks on EGB and DM search • “New” EGB spectrum in 0.2-100 GeV • Blazars account for <40% of EGB • room for star-forming galaxies, normal AGNs or truly diffuse • No evidence for DM annihilation • Constraints on models, in particular m+/m- channel • Astrophysical source contribution is important

  42. Cosmic-Ray Electrons

  43. PAMELA Positron Excess • Convincing evidence of e+ ratio excess in >10 GeV • 2ndary e+ should be softer than primary e- Sources of “Primary” e+ are required Adriani+08 0.1 1 GeV 10 100

  44. CRE by Fermi-LAT (2009) • Fermi-LAT reported hard e- + e+ spectrum • Standard models with proper choice of params are able to reproduce Fermi data alone, but not Fermi + PAMELA 6 months data 4.5 M events Abod+09 PRL 102, 181101 (CA: Latronico, Moiseev) Fermi Data (2009) 10 100 1000 GeV

  45. e-/e+ probe nearby sources • CR e-/e+ loose energy via synchrotron and IC, hence probe nearby sources We are here Our Galaxy e+ sources KEK 井岡氏の トラぺより借用

  46. CRE by Fermi-LAT (2010) • CREs collected for 12 month (data is doubled) • Cross-check with events with long path in CAL (>=13X0) • LE extention using high latitude (low cutoff) data • Noticeable deviation from a single PL 20 GeV Fermi Data (2010) pre-Fermi model Ackermann+10 PRD 82, 092004 (CA: Moiseev, Sgro) 1 10 100 GeV 1000

  47. CRE by Fermi-LAT (2010) • Noticeable deviation from a single PL • Additional e-/e+ sources (astrophysical or extocis) can provide a good fit to Fermi CRE and PAMELA e+/(e- + e+) Anisotropy of arrival direction may reveal sources or give constraints Example of an additional component Ackermann+10 PRD 82, 092004 (CA: Moiseev, Sgro) 1 10 100 GeV 1000

  48. CRE Anisotropy No-anisotropy map • Construct no anisotropy map from flight data • shuffling and direct integration • Compare obtained map with data • search for anisotoropy Eth: 60-480 GeV Angular scale: 10-90 deg Flight data sky map No evidence of anisotropy in energies/angles investigated Significance map Ackermann+10 PRD 82, 092003 (CA: Mazziotta, Vasileiou)

  49. Limit on Sources • No evidence of anisotropies • Upper limit for the dipole anisotropy: 0.5-5% • Limit already comparable to the value expected for a single nearby source dominating HE spectrum • will improve as more data are collected Dipole Anisotropy CRE spectrum at Earth Fermi (3s UL) Fermi HESS Monogem Vela Vela Monogem Ackermann+10 PRD 82, 092003 (CA: Mazziotta, Vasileiou)

  50. Summary • Diffuse g-ray emission is a powerful probe for studying CRs and ISM • Constraints on some DM models. Study of diffuse g-rays and g-ray object is important • UL of CR anisotropy is close to what is expected for single nearby source Thank you for your Attention

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