We present the analysis of the interstellar γ-ray emission measured by the Fermi Large Area Telescope toward a region in the second Galactic quadrant at 100° ≤ l ≤ 145° and –15° ≤ b ≤ +30°. This region encompasses the prominent Gould Belt clouds of Cassiopeia, Cepheus, and the Polaris flare, as well as atomic and molecular complexes at larger distances, like that associated with NGC 7538 in the Perseus arm. The good kinematic separation in velocity between the local, Perseus, and outer arms, and the presence of massive complexes in each of them, make this region well suited to probe cosmic rays (CRs) and the interstellar medium beyond the solar circle. The γ-ray emissivity spectrum of the gas in the Gould Belt is consistent with expectations based on the locally measured CR spectra. The γ-ray emissivity decreases from the Gould Belt to the Perseus arm, but the measured gradient is flatter than expectations for CR sources peaking in the inner Galaxy as suggested by pulsars. The X CO = N(H2)/W CO conversion factor is found to increase from (0.87 ± 0.05) × 1020 cm–2 (K km s–1)–1 in the Gould Belt to (1.9 ± 0.2) × 1020 cm–2 (K km s–1)–1 in the Perseus arm. We derive masses for the molecular clouds under study. Dark gas, not properly traced by radio and microwave surveys, is detected in the Gould Belt through a correlated excess of dust and γ-ray emission: its mass amounts to ~50% of the CO-traced mass.
|Autori:||Abdo AA; Ackermann M; Ajello M; Baldini L; Ballet J; Barbiellini G; Bastieri D; Baughman BM; Bechtol K; Bellazzini R; Berenji B; Bloom ED; Bonamente E; Borgland AW; Bregeon J; Brez A; Brigida M; Bruel P; Burnett TH; Buson S; Caliandro GA; Cameron RA; Caraveo PA; Casandjian JM; Cecchi C; Celik O; Chekhtman A; Cheung CC; Chiang J; Ciprini S; Claus R; Cohen-Tanugi J; Cominsky LR; Conrad J; Dermer CD; de Palma F; Digel SW; Silva EDE; Drell PS; Dubois R; Dumora D; Farnier C; Favuzzi C; Fegan SJ; Focke WB; Fortin P; Frailis M; Fukazawa Y; Funk S; Fusco P; Gargano F; Gehrels N; Germani S; Giavitto G; Giebels B; Giglietto N; Giordano F; Glanzman T; Godfrey G; Grenier IA; Grondin MH; Grove JE; Guillemot L; Guiriec S; Harding AK; Hayashida M; Horan D; Hughes RE; Jackson MS; Johannesson G; Johnson AS; Johnson WN; Kamae T; Katagiri H; Kataoka J; Kawai N; Kerr M; Knodlseder J; Kuss M; Lande J; Latronico L; Lemoine-Goumard M; Longo F; Loparco F; Lott B; Lovellette MN; Lubrano P; Makeev A; Mazziotta MN; McEnery JE; Meurer C; Michelson PF; Mitthumsiri W; Mizuno T; Monte C; Monzani ME; Morselli A; Moskalenko IV; Murgia S; Nolan PL; Norris JP; Nuss E; Ohsugi T; Okumura A; Omodei N; Orlando E; Ormes JF; Paneque D; Pelassa V; Pepe M; Pesce-Rollins M; Piron F; Porter TA; Raino S; Rando R; Razzano M; Reimer A; Reimer O; Reposeur T; Rodriguez AY; Ryde F; Sadrozinski HFW; Sanchez D; Sander A; Parkinson PMS; Sgro C; Siskind EJ; Smith PD; Spandre G; Spinelli P; Starck JL; Strickman MS; Strong AW; Suson DJ; Takahashi H; Tanaka T; Thayer JB; Thayer JG; Thompson DJ; Tibaldo L; Torres DF; Tosti G; Tramacere A; Uchiyama Y; Usher TL; Vasileiou V; Vilchez N; Vitale V; Waite AP; Wang P; Winer BL; Wood KS; Ylinen T; Ziegler M|
|Titolo:||FERMI OBSERVATIONS OF CASSIOPEIA AND CEPHEUS: DIFFUSE GAMMA-RAY EMISSION IN THE OUTER GALAXY|
|Anno del prodotto:||2010|
|Digital Object Identifier (DOI):||10.1088/0004-637X/710/1/133|
|Appare nelle tipologie:||1.1 Articolo in rivista|