The Fermi bubbles are two large structures in the gamma-ray sky extending to 55 degrees above and below the Galactic center. We analyze 50 months of Fermi Large Area Telescope data between 100MeV and 500 GeV above 10 degrees in Galactic latitude to derive the spectrum and morphology of the Fermi bubbles. We thoroughly explore the systematic uncertainties that arise when modeling the Galactic diffuse emission through two separate approaches. The gamma-ray spectrum is well described by either a log parabola or a power law with an exponential cutoff. We exclude a simple power law with more than 7 sigma significance. The power law with an exponential cutoff has an index of 1.9 +/- 0.2 and a cutoff energy of 110 +/- 50 GeV. We find that the gamma-ray luminosity of the bubbles is 4.4(-0.9)(+2.4) x 10(37) erg s(-1). We confirm a significant enhancement of gamma-ray emission in the southeastern part of the bubbles, but we do not find significant evidence for a jet. No significant variation of the spectrum across the bubbles is detected. The width of the boundary of the bubbles is estimated to be 3.4(-2.6)(+3.7) deg. Both inverse Compton (IC) models and hadronic models including IC emission from secondary leptons fit the gamma-ray data well. In the IC scenario, synchrotron emission from the same population of electrons can also explain the WMAP and Planck microwave haze with a magnetic field between 5 and 20 mu G.
THE SPECTRUM AND MORPHOLOGY OF THE FERMI BUBBLES / Ackermann M; Albert A; Atwood WB; Baldini L; Ballet J; Barbiellini G; Bastieri D; Bellazzini R; Bissaldi E; Blandford RD; Bloom ED; Bottacini E; Brandt TJ; Bregeon J; Bruel P; Buehler R; Buson S; Caliandro GA; Cameron RA; Caragiulo M; Caraveo PA; Cavazzuti E; Cecchi C; Charles E; Chekhtman A; Chiang J; Chiaro G; Ciprini S; Claus R; Cohen-Tanugi J; Conrad J; Cutini S; DAmmando F; de Angelis A; de Palma F; Dermer CD; Digel SW; Di Venere L; Silva EDE; Drell PS; Favuzzi C; Ferrara EC; Focke WB; Franckowiak A; Fukazawa Y; Funk S; Fusco P; Gargano F; Gasparrini D; Germani S; Giglietto N; Giordano F; Giroletti M; Godfrey G; Gomez-Vargas GA; Grenier IA; Guiriec S; Hadasch D; Harding AK; Hays E; Hewitt JW; Hou X; Jogler T; Johannesson G; Johnson AS; Johnson WN; Kamae T; Kataoka J; Knodlseder J; Kocevski D; Kuss M; Larsson S; Latronico L; Longo F; Loparco F; Lovellette MN; Lubrano P; Malyshev D; Manfreda A; Massaro F; Mayer M; Mazziotta MN; McEnery JE; Michelson PF; Mitthumsiri W; Mizuno T; Monzani ME; Morselli A; Moskalenko IV; Murgia S; Nemmen R; Nuss E; Ohsugi T; Omodei N; Orienti M; Orlando E; Ormes JF; Paneque D; Panetta JH; Perkins JS; Pesce-Rollins M; Petrosian V; Piron F; Pivato G; Raino S; Rando R; Razzano M; Razzaque S; Reimer A; Reimer O; Sanchez-Conde M; Schaal M; Schulz A; Sgro C; Siskind EJ; Spandre G; Spinelli P; Stawarz L; Strong AW; Suson DJ; Tahara M; Takahashi H; Thayer JB; Tibaldo L; Tinivella M; Torres DF; Tosti G; Troja E; Uchiyama Y; Vianello G; Werner M; Winer BL; Wood KS; Wood M; Zaharijas G. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - STAMPA. - 793:1(2014), pp. 64.64-64.97. [10.1088/0004-637X/793/1/64]
THE SPECTRUM AND MORPHOLOGY OF THE FERMI BUBBLES
D'AMMANDO, FILIPPO;
2014
Abstract
The Fermi bubbles are two large structures in the gamma-ray sky extending to 55 degrees above and below the Galactic center. We analyze 50 months of Fermi Large Area Telescope data between 100MeV and 500 GeV above 10 degrees in Galactic latitude to derive the spectrum and morphology of the Fermi bubbles. We thoroughly explore the systematic uncertainties that arise when modeling the Galactic diffuse emission through two separate approaches. The gamma-ray spectrum is well described by either a log parabola or a power law with an exponential cutoff. We exclude a simple power law with more than 7 sigma significance. The power law with an exponential cutoff has an index of 1.9 +/- 0.2 and a cutoff energy of 110 +/- 50 GeV. We find that the gamma-ray luminosity of the bubbles is 4.4(-0.9)(+2.4) x 10(37) erg s(-1). We confirm a significant enhancement of gamma-ray emission in the southeastern part of the bubbles, but we do not find significant evidence for a jet. No significant variation of the spectrum across the bubbles is detected. The width of the boundary of the bubbles is estimated to be 3.4(-2.6)(+3.7) deg. Both inverse Compton (IC) models and hadronic models including IC emission from secondary leptons fit the gamma-ray data well. In the IC scenario, synchrotron emission from the same population of electrons can also explain the WMAP and Planck microwave haze with a magnetic field between 5 and 20 mu G.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
