FERMI LARGE AREA TELESCOPE STUDY OF COSMIC RAYS AND THE INTERSTELLAR MEDIUM IN NEARBY MOLECULAR CLOUDS-猫眼课题宝

DOI：

10.1088/0004-637x/755/1/22

发表时间：

2012-08

期刊：

The Astrophysical Journal

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

M. Ackermann;M. Ajello;A. Allafort;L. Baldini;J. Ballet;G. Barbiellini;D. Bastieri;K. Bechtol;R. Bellazzini;B. Berenji;R. Blandford;E. Bloom;E. Bonamente;A. Borgland;E. Bottacini;T. Brandt;J. Bregeon;M. Brigida;P. Bruel;R. Buehler;G. Busetto;S. Buson;G. Caliandro;R. Cameron;P. Caraveo;J. Casandjian;C. Cecchi;E. Charles;A. Chekhtman;J. Chiang;S. Ciprini;R. Claus;J. Cohen-Tanugi;J. Conrad;F. D’Ammando;A. Angelis;F. Palma;C. Dermer;S. Digel;E. Silva;P. Drell;A. Drlica-Wagner;L. Falletti;C. Favuzzi;S. Fegan;E. Ferrara;W. Focke;Y. Fukazawa;Y. Fukui;S. Funk;P. Fusco;F. Gargano;D. Gasparrini;S. Germani;N. Giglietto;F. Giordano;M. Giroletti;T. Glanzman;G. Godfrey;I. Grenier;M. Grondin;J. Grove;S. Guiriec;D. Hadasch;Y. Hanabata;A. Harding;K. Hayashi;D. Horan;X. Hou;R. Hughes;R. Itoh;M. Jackson;G. Jóhannesson;A. Johnson;T. Kamae;H. Katagiri;J. Kataoka;J. Knödlseder;M. Kuss;J. Lande;S. Larsson;Suk-Han Lee;M. Lemoine-Goumard;F. Longo;F. Loparco;M. Lovellette;P. Lubrano;P. Martin;M. Mazziotta;J. Mcenery;J. Méhault;P. Michelson;W. Mitthumsiri;T. Mizuno;A. Moiseev;C. Monte;M. Monzani;A. Morselli;I. Moskalenko;S. Murgia;M. Naumann-Godo;R. Nemmen;S. Nishino;J. Norris;E. Nuss;M. Ohno;T. Ohsugi;A. Okumura;N. Omodei;E. Orlando;J. Ormes;M. Ozaki;D. Paneque;J. Panetta;D. Parent;M. Pesce-Rollins;M. Pierbattista;F. Piron;G. Pivato;T. Porter;S. Rainò;R. Rando;M. Razzano;A. Reimer;O. Reimer;C. Romoli;M. Roth;T. Sada;H. Sadrozinski;D. Sanchez;C. Sbarra;C. Sgro’;E. Siskind;G. Spandre;P. Spinelli;A. Strong;D. Suson;H. Takahashi;Tadayuki Takahashi;Takaaki Tanaka;J. Thayer;J. Thayer;D. Thompson;L. Tibaldo;O. Tibolla;M. Tinivella;D. Torres;G. Tosti;A. Tramacere;E. Troja;Y. Uchiyama;T. Uehara;T. Usher;J. Vandenbroucke;V. Vasileiou;G. Vianello;V. Vitale;A. Waite;Pengfei Wang;B. Winer;K. Wood;H. Yamamoto;Zhirong Yang;S. Zimmer

利用费米大面积望远镜对变色龙、南冕R （R CrA）、仙王座和北极星耀斑区域的星际γ射线发射进行了分析。它们是最近的分子云复合体之一，距离太阳系不到300pc。在这些分子云中，宇宙射线与星际气体相互作用产生的γ射线辐射对研究靠近太阳系的分子气体的CR密度和分布是有用的。得到的250 MeV以上的γ射线发射率分别为（5.9±0.1stat +0.9−1.0sys） × 10−27光子s−1 sr−1 h原子- 1、（10.2±0.4stat +1.2−1.7sys） × 10−27光子s−1 sr−1 h原子- 1和（9.1±0.3stat +1.5−0.6sys） × 10−27光子s−1 sr−1 h原子- 1，分别为变色龙、R CrA、仙王和北极星耀斑区域。尽管发射率的能量依赖性与地球上直接CR观测预测的结果吻合得很好，但从250 MeV到10 GeV的测量发射率表明，即使考虑到系统的不确定性，在太阳系附近CR密度的变化也会达到~ 20%。在变色龙、R CrA、仙王座和北极星耀斑区域，分子质量校准比XCO = N(H2)/WCO分别为（0.96±0.06stat +0.15−0.12sys） × 1020 H2-分子cm−2 (K km s−1)−1、（0.99±0.08stat +0.18−0.10sys） × 1020 H2-分子cm−2 (K km s−1)−1和（0.63±0.02stat +0.09−0.07sys） × 1020 H2-分子cm−2 (K km s−1)−1，表明XCO在太阳系附近有变化。根据获得的XCO值，WCO在变色龙、R CrA、仙王座和北极星耀斑区域追踪到的分子气体质量估计分别为~ 5 × 103 M☉、~ 103 M☉和~ 3.3 × 104 M☉。在被调查的地区发现了相当数量的气体，而不是通过标准的氢和一氧化碳测量来追踪的。

We report an analysis of the interstellar γ-ray emission from the Chamaeleon, R Coronae Australis (R CrA), and Cepheus and Polaris flare regions with the Fermi Large Area Telescope. They are among the nearest molecular cloud complexes, within ∼300 pc from the solar system. The γ-ray emission produced by interactions of cosmic rays (CRs) and interstellar gas in those molecular clouds is useful to study the CR densities and distributions of molecular gas close to the solar system. The obtained γ-ray emissivities above 250 MeV are (5.9 ± 0.1stat +0.9−1.0sys) × 10−27 photons s−1 sr−1 H-atom−1, (10.2 ± 0.4stat +1.2−1.7sys) × 10−27 photons s−1 sr−1 H-atom−1, and (9.1 ± 0.3stat +1.5−0.6sys) × 10−27 photons s−1 sr−1 H-atom−1 for the Chamaeleon, R CrA, and Cepheus and Polaris flare regions, respectively. Whereas the energy dependences of the emissivities agree well with that predicted from direct CR observations at the Earth, the measured emissivities from 250 MeV to 10 GeV indicate a variation of the CR density by ∼20% in the neighborhood of the solar system, even if we consider systematic uncertainties. The molecular mass calibrating ratio, XCO = N(H2)/WCO, is found to be (0.96 ± 0.06stat +0.15−0.12sys) × 1020 H2-molecule cm−2 (K km s−1)−1, (0.99 ± 0.08stat +0.18−0.10sys) × 1020 H2-molecule cm−2 (K km s−1)−1, and (0.63 ± 0.02stat +0.09−0.07sys) × 1020 H2-molecule cm−2 (K km s−1)−1 for the Chamaeleon, R CrA, and Cepheus and Polaris flare regions, respectively, suggesting a variation of XCO in the vicinity of the solar system. From the obtained values of XCO, the masses of molecular gas traced by WCO in the Chamaeleon, R CrA, and Cepheus and Polaris flare regions are estimated to be ∼5 × 103 M☉, ∼103 M☉, and ∼3.3 × 104 M☉, respectively. A comparable amount of gas not traced well by standard H i and CO surveys is found in the regions investigated.

FERMI LARGE AREA TELESCOPE STUDY OF COSMIC RAYS AND THE INTERSTELLAR MEDIUM IN NEARBY MOLECULAR CLOUDS

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