Fermi LAT Observations of Galactic and Extragalactic Diffuse Emission Jean-Marc Casandjian, on...

Click here to load reader

  • date post

    15-Jan-2016
  • Category

    Documents

  • view

    223
  • download

    0

Embed Size (px)

Transcript of Fermi LAT Observations of Galactic and Extragalactic Diffuse Emission Jean-Marc Casandjian, on...

  • 7 questions addressed during this presentationWhat are the origins of the Milky-Way -ray diffuse emission ?Is the cosmic ray (CR) density uniform within ~1 kpc from the sun ?How does the CR density vary with the Galactocentric distance ? Are the CR and ISM density coupled ?Does FERMI see the EGRET GeV excess ?Can we model the Galactic diffuse emission ?Can the EGB be explained by unresolved AGN ?

  • 100%11%

  • 100%89%

  • What are the origins of the Milky-Way -ray diffuse emission ?1.

  • Diffuse Emission : study of CR, ISM and ISRFProcesses for HE production :

  • Abdo et al., ApJ 703, 1249 (2009), C.A.: T. MizunoNo H2, intensity is proportional to HI column density -ray intensities (sources and IC removed) versus HI column densities200 l 260 , 22 |b| 60

  • 89%LAT minus sources

  • 74%LAT minus sources, isotropic

  • 26%LAT minus sources, isotropic, HI

  • 17%LAT minus sources, isotropic, HI, H2

  • The diffuse emission can be modelled with a linear combination of various templates

  • Is the cosmic ray density uniform within ~1 kpc from the sun ?3 regions were investigated:

    200 l 260 , 22 |b| 60 Abdo et al., ApJ 703, 1249 (2009), C.A.: T. Mizuno100 l 145 , -15 b 30 (local arm) Abdo et al., ApJ 710, 133 (2010) C.A.: L. Tibaldo, I. Grenier210 l 250 , -15 b 20 (local arm) Abdo et al., submitted, C.A.: T. Mizuno, L. Tibaldo, I. Grenier2.

  • 200 l 260 , 22 |b| 60100 l 145 , -15 b 30210 l 250 , -15 b 20Preliminary

  • It is uniform within systematics the local CR nuclei spectra are close to those directly measured at the EarthIs the cosmic ray density uniform within ~1 kpc from the sun ?

  • How does the CR density vary with the Galactocentric distance ?

    3.2 regions were investigated:

    100 l 145 , -15 b 30 Abdo et al., ApJ 710, 133 (2010) C.A.: L. Tibaldo, I. Grenier210 l 250 , -15 b 20 Abdo et al., submitted, C.A.: T. Mizuno, L. Tibaldo, I. Grenier

  • Preliminaryflat source distribution in R>=Rbk (dotted line)SNR distribution (solid line)Zh=1, 2, 4, 10, 15 and 20 kpcPreliminaryVarying the HALO sizeVarying the source distribution100 l 145 , -15 b 30210 l 250 , -15 b 20

  • How does the CR density vary with the Galactocentric distance ?

    Decrease of CR densities but with a gradient flatter than expectations for SNR sources as traced by PSR -> larger halo ?

  • Are the CR and ISM density coupled ?Association of CR sources with regions of massive clouds ?Confinement of CRs by magnetic fields associated with the gas ?4.

    is there an arm/inter arm CR effect velocity-longitude profile of HI emissionLocalInter armPerseus arm

  • Are the CR and ISM density coupled ?Abdo et al., submitted, C.A.: T. Mizuno, L. Tibaldo, I. GrenierSystematics related to HI spin temperaturearmarminter-arm{{{

  • Are the CR and ISM density coupled ?No large enhancement in the spiral arms with respect to the interarm region

  • Does FERMI see the EGRET GeV excess ?5.

  • Does FERMI see the EGRET GeV excess ?

  • Can we model the large scale structures of the Galactic interstellar emission ?6.

  • Can the EGB be explained by unresolved AGN ?7.

  • Can the EGB be explained by unresolved AGN ?

  • Possible origins of the EGB :blazars, star forming galaxies, radio-quiet AGN, millisecond pulsars, intergalactic shocks, dark matter annihilation, UHECR interacting with EBL ...Can the EGB be explained by unresolved AGN ?

  • LogN-logSBlazars account for
  • Star Forming GalaxiesFields,Pavlidou,Pradanovic 2010

  • Conclusion7 answers given during this presentationWith the diffuse emission we study the CR, ISM and ISRF.The CR density is uniform within ~1 kpc from the sun.We observe a flatter than expected decrease of the CR density with the Galactocentric distance.No sign of coupling between CR and ISM density was observed.No FERMI GeV excess.We can model the Galactic diffuse emission with Galprop.Unresolved AGN can not explain all the EGB.

    Four regions were defined in Galactocentric distance, namely the Local arm (Galactocentric radius R 10 kpc), the interarm region (R = 1012.5 kpc), the Perseus arm (R = 12.516 kpc) and the region beyond the Perseus arm (which hosts a faint segment of the outer arm; R 16 kpc).avec le logN-logS et simulation on ne descend pas plus faible intensit mais on met les sources qui ne sont pas detecte car coupure spectrale:les sources soft avec flux faibles se perdent dans lemission diffuse (ou extra-gal) -> avec la simul on peut estimer leur flux.