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arXiv 1207.0616astro-ph.HEastro-ph.GA
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用费米大面积望远镜对猎户座分子云的Gamma-ray观测

Gamma-ray observations of the Orion Molecular Clouds with the Fermi Large Area Telescope

M. Ackermann, M. Ajello, A. Allafort, E. Antolini, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, R. D. Blandford, E… 展开作者

M. Ackermann, M. Ajello, A. Allafort, E. Antolini, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, R. D. Blandford, E. D. Bloom, E. Bonamente, A. W. Borgland, E. Bottacini, T. J. Brandt, J. Bregeon, M. Brigida, P. Bruel, R. Buehler, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, C. Cecchi, A. Chekhtman, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, J. Conrad, F. D'Ammando, A. de Angelis, F. de Palma, C. D. Dermer, E. do Couto e Silva, P. S. Drell, A. Drlica-Wagner, T. Enoto, L. Falletti, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, Y. Fukazawa, Y. Fukui, P. Fusco, F. Gargano, D. Gasparrini, S. Germani, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, S. Guiriec, D. Hadasch, Y. Hanabata, A. K. Harding, M. Hayashida, K. Hayashi, D. Horan, X. Hou, R. E. Hughes, M. S. Jackson, G. Jóhannesson, A. S. Johnson, T. Kamae, H. Katagiri, J. Kataoka, M. Kerr, J. Knödlseder, M. Kuss, J. Lande, S. Larsson, S. -H. Lee, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, K. Makishima, M. N. Mazziotta, J. Mehault, W. Mitthumsiri, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, T. Nakamori, M. Naumann-Godo, S. Nishino, J. P. Norris, E. Nuss, M. Ohno, T. Ohsugi, A. Okumura, M. Orienti, E. Orlando, J. F. Ormes, M. Ozaki, D. Paneque, J. H. Panetta, D. Parent, V. Pelassa, M. Pesce-Rollins, M. Pierbattista, F. Piron, G. Pivato, T. A. Porter, S. Rainò, M. Razzano, A. Reimer, O. Reimer, M. Roth, H. F. -W. Sadrozinski, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, A. W. Strong, H. Takahashi, T. Takahashi, T. Tanaka, J. G. Thayer, J. B. Thayer, O. Tibolla, M. Tinivella, D. F. Torres, A. Tramacere, E. Troja, Y. Uchiyama, T. L. Usher, J. Vandenbroucke, V. Vasileiou, G. Vianello, V. Vitale, A. P. Waite, P. Wang, B. L. Winer, K. S. Wood, Z. Yang, S. Zimmer

摘要:

本文报道了用费米伽马射线空间望远镜上的大视场望远镜(LAT)对猎户座A和B巨大分子云的伽马射线观测。在\sim 100 MeV和\sim 100 GeV之间的能带中的γ射线发射被预测为通过银河系宇宙射线(CR)与星际气体之间的核相互作用来追踪云中的气体质量分布。核相互作用的γ射线产生截面已知为\sim 10%的精度,这使得LAT成为测量已知CR强度的分子云的气体质量柱密度分布的有力工具。我们在这里提出这样的分布猎户座A和B,并将它们与速度积分CO强度(WCO)在1° \times 1°像素水平。当被分成3个区域时,发现在~10倍的WCO范围内的相关性是线性的,这表明核CRs渗透到大多数云体积中。猎户座A的高经度部分(l > 212°)的Wco-质量转换因子Xco为\sim 2.3 \times 10^20 cm-2(K km s-1)-1,比猎户座A和B的其余部分的\sim 1.3 \times 10^20高1.7倍。我们解释了明显的高XCO在高经度地区的猎户座A在最近的工作提出了一个非线性关系的扩散分子气体中的H2和CO密度。在使气体比Wco“更暗”的区域中,Wco比H2柱密度降低得更快。

英文摘要:

We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between \sim100 MeV and \sim100 GeV is predicted to trace the gas mass distribution in the clouds through nuclear interactions between the Galactic cosmic rays (CRs) and interstellar gas. The gamma-ray production cross-section for the nuclear interaction is known to \sim10% precision which makes the LAT a powerful tool to measure the gas mass column density distribution of molecular clouds for a known CR intensity. We present here such distributions for Orion A and B, and correlate them with those of the velocity integrated CO intensity (WCO) at a 1° \times1° pixel level. The correlation is found to be linear over a WCO range of ~10 fold when divided in 3 regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The Wco-to-mass conversion factor, Xco, is found to be \sim2.3\times10^20 cm-2(K km s-1)-1 for the high-longitude part of Orion A (l > 212°), \sim1.7 times higher than \sim1.3 \times 10^20 found for the rest of Orion A and B. We interpret the apparent high Xco in the high-longitude region of Orion A in the light of recent works proposing a non-linear relation between H2 and CO densities in the diffuse molecular gas. Wco decreases faster than the H2 column density in the region making the gas "darker" to Wco.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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