1. Interstellar gamma-rays: first large-scale results from Fermi-LAT Andy Strong on behalf of Fermi-LAT collaboration ICRC Lodz 7-15 July 2009 OG2.1 ID 0390

2. SCOPE: preliminary evaluation of Fermi-LAT data comparing with models of diffuse interstellar emission What are the first lessons we have learned ?

3. Fermi results on diffuse gamma-rays at this ICRC: Julie McEnery Fermi overview highlight talk Troy Porter: Intermediate latitudes, EGRET comparison POSTER This session: Luigi Tibaldi : 2 nd Galactic quadrant Akira Okumura: Orion clouds Markus Ackermann: Extragalactic background Troy Porter: Large Magellanic Cloud also in progress: Tsufune Mizuno HI emissivity analysis Jean-Marc Cassandjian Galactic Rings analysis ALL ONGOING WORK see also synchrotron for the same model, Orlando et al. this ICRC

4. Fermi 3 month skymap

5. Abdo et al. in preparation for the Fermi-LAT Collaboration Fermi does not confirm GeV excess seen by EGRET EGRET Fermi-LAT The two experiments have different instrumental backgrounds, so this comparison is not exact, but the difference is not mainly attributable to this. P R E L I M I N A R Y see poster 0554 (Troy Porter)

6. Abdo et al. in preparation for the Fermi-LAT Collaboration Fermi-LAT model detected sources inverse Compton bremsstrahlung isotropic (instrumental + astrophysical) model based on local cosmic-ray spectra (but pre-Fermi electrons)..... agrees with Fermi ! Intermediate latitudes: mainly emission within 1 kpc -> local cosmic rays Small, uniform excess can be due to uncertainties in cosmic rays, gas surveys, unresolved sources, etc. P R E L I M I N A R Y  o -decay see poster 0554 by Troy Porter INTERMEDIATE GALACTIC LATITUDES 10 o < b < 20 o

7. Modelling the gamma-ray sky main ingredients: cosmic-ray spectra p, He, e-, e+ (including secondaries) (NB here using Fermi-measured electrons) cosmic-ray source distribution follows SNR/pulsars B/C etc for propagation parameters halo height = 4 kpc (from radioactive nuclei) Interstellar radiation field HI, CO surveys CO-to-H2 conversion a function of position in Galaxy Fermi bright source list Uses GALPROP latest version: poster, this ICRC

8. PROTONS ELECTRONS = Fermi First use a model based on locally-measured cosmic rays

9. Gas Rings: HI Inner & Outer Galaxy Gas Rings: HI Local Galaxy

10. Interstellar Radiation Field (for electron dE/dt, inverse Compton  -rays): new model (Troy Porter) R = 0 R = 12 kpc R = 4 kpc UV optical IR FIR CMB

11. a priori model with Fermi electron spectrum INNER GALAXY spectral shape OK systematically low need to increase cosmic rays pion decay isotropic bremsstrahlung inverse Compton Fermi LAT bright source list PRELIMINARY isotropic* * isotropic = instrumental plus astrophysical backgrounds

12. a priori model with Fermi electron spectrum LONGITUDE PROFILE generally too low LATITUDE PROFILE 400 MeV PRELIMINARY

13. not bad for an a priori model prediction but generally too low this means either more CR electrons and/or protons model fitting guides us to a better model: electrons increased by factor ~2 protons increased by ~15% ------------->

14. PROTONS ELECTRONS = Fermi Improving the model with increased CR

15. pion-decay bremsstrahlung isotropic* inverse Compton Fermi model adjusted to Fermi INNER GALAXY statistical +systematic errors Fermi LAT bright source list ( Gulli's |b|>30 isotropic-fixed fit for this plot ) PRELIMINARY * isotropic = instrumental plus astrophysical backgrounds

16. Model adjusted to Fermi LONGITUDE PROFILE LATITUDE PROFILE quite good, latitude fits from plane to poles over 2 decades dynamic range importance of inverse Compton at high latitudes : gamma-ray halo ! 400 MeV HIHI H2 IC bright source list total HIHI H2 IC isotropic PRELIMINARY profiles have isotropic gardian fixed-fit unresolved sources may contribute and make up difference, not included !

17. Model adjusted to Fermi LONGITUDE PROFILE LATITUDE PROFILE quite good, latitude fits from plane to poles over 2 decades dynamic range importance of inverse Compton at high latitudes : gamma-ray halo ! 1.3 GeV HIHI H2 IC bright source list total HIHI H2 IC isotropic PRELIMINARY profiles have isotropic gardian fixed-fit

18. Model adjusted to Fermi LONGITUDE PROFILE LATITUDE PROFILE quite good, latitude fits from plane to poles over 2 decades dynamic range importance of inverse Compton at high latitudes : gamma-ray halo ! 12 GeV HIHI H2 IC bright source list total HIHI H2 IC isotropic PRELIMINARY profiles have isotropic gardian fixed-fit

19. Model adjusted to Fermi LONGITUDE PROFILE LATITUDE PROFILE quite good, latitude fits from plane to poles over 2 decades dynamic range importance of inverse Compton at high latitudes : gamma-ray halo ! 400 MeV HIHI H2 IC bright source list total HIHI H2 IC isotropic PRELIMINARY NEW:including Fermi-based Xco, CR gradient latitude profile has isotropic gardian fixed-fit

20. CONCLUSIONS Fermi does not confirm EGRET GeV excess a priori model: agrees with Fermi at intermediate latitudes has correct spectral shape but is rather low in the inner Galaxy generally reasonable fit with simple scaling of CR protons, electrons over the sky and wide energy range increased protons consistent with local CR data increased electrons inconsistent with local CR data (including Fermi-measured) increased inverse Compton : more electrons OR more ISRF or..... ? inverse Compton component at high latitudes : CR halo ! evidence for 'Dark gas' not traced by HI, CO THESE RESULTS ARE PRELIMINARY - ONGOING WORK !

21. END

22. backup slides

23. a priori model INTERMEDIATE LATITUDES here using electrons measured by Fermi agreement good within uncertainties on cosmic-ray spectra gas surveys pion decay inverse Compton bremsstrahlung isotropic total Fermi statistical +systematic errors Fermi LAT bright source list PRELIMINARY this region + this region Fermi-LAT DATA: 8 months, DIFFUSE class

24. a priori model LONGITUDE PROFILE generally too low LATITUDE PROFILE PRELIMINARY 1.3 GeV

25. Galactic metallicity gradient e.g. [O/H] metallicity decreases with R, X= H 2 / CO decreases with metallicity >>>>>> X = H 2 / CO increases with radius -rays = CR sources(R) * X(R) *CO(R) (+ HI, inverse Compton terms) Strong et al. 2004 A&A 422,L47 SNR (traced by latest pulsar surveys) X= H 2 /CO

26. Preliminary tuning to Fermi data cosmic-ray distribution Xco OLD Fermi pulsars/SNR Fermi

27. ELECTRONS = Fermi from Grasso et al., could use this plot instead.

28. model adjusted to Fermi INTERMEDIATE LATITUDES (Gulli's |b|>30 isotropic free for this model) PRELIMINARY

29. Plan (for me, not to be shown). Fermi-LAT data Models a priori compare with data spectrum longitude profile latitude profile tuned compared with data spectrum longitude profile latitude profile Other analyses at this ICRC and elsewhere. What we learned physical model quite good but needs adjusting need more electrons – or ISRF Xco gradient confirmed but less than before CR consistent with SNR/pulsars This is all ongoing work. Notes The idea is physical model comparison Just the top-level results Based on Diffuse Group Paper 2 in preparation and other results from Diffuse group at ICRC Time is 10 min including discussion so need to be short and simple (does not yet satisfy these criteria)