Observations of M31 and M33 with the Fermi Large Area Telescope: A Galactic Center Excess in Andromeda?
文献类型：期刊论文
| 作者 | Ackermann, M.1; Ajello, M.2; Albert, A.3; Baldini, L.4; Ballet, J.5; Barbiellini, G.6,7; Bastieri, D.8,9; Bellazzini, R.10; Bissaldi, E.11; Bloom, E. D.12 |
| 刊名 | ASTROPHYSICAL JOURNAL
 |
| 出版日期 | 2017-02-20 |
| 卷号 | 836期号:2 |
| ISSN号 | 0004-637X |
| 关键词 | cosmic rays gamma rays: galaxies Local Group |
| 通讯作者 | Hou, X.(Chinese Acad Sci, Yunnan Observ, 396 Yangfangwang, Kunming 650216, Peoples R China) |
| 产权排序 | 第34完成单位 |
| 英文摘要 | The Fermi Large Area Telescope (LAT) has opened the way for comparative studies of cosmic rays (CRs) and high-energy objects in the Milky Way (MW) and in other, external, star-forming galaxies. Using 2 yr of observations with the Fermi LAT, Local Group galaxy M31 was detected as a marginally extended gamma-ray source, while only an upper limit has been derived for the other nearby galaxy M33. We revisited the gamma-ray emission in the direction of M31 and M33 using more than 7 yr of LAT Pass 8 data in the energy range 0.1-100 GeV, presenting detailed morphological and spectral analyses. M33 remains undetected, and we computed an upper limit of 2.0 x 10(-12) erg cm(-2) s(-1) on the 0.1-100 GeV energy flux (95% confidence level). This revised upper limit remains consistent with the observed correlation between gamma-ray luminosity and star formation rate tracers and implies an average CR density in M33 that is at most half of that of the MW. M31 is detected with a significance of nearly 10 sigma. Its spectrum is consistent with a power law with photon index Gamma = 2.4 +/- 0.1(stat) (vertical bar) (syst) and a 0.1-100 GeV energy flux of (5.6 +/- 0.6(stat vertical bar syst)) x 10(-12) erg cm(-1) s(-1). M31 is detected to be extended with a 4 sigma significance. The spatial distribution of the emission is consistent with a uniform-brightness disk with a radius of 0 degrees.4 and no offset from the center of the galaxy, but nonuniform intensity distributions cannot be excluded. The flux from M31 appears confined to the inner regions of the galaxy and does not fill the disk of the galaxy or extend far from it. The gamma-ray signal is not correlated with regions rich in gas or star formation activity, which suggests that the emission is not interstellar in origin, unless the energetic particles radiating in gamma rays do not originate in recent star formation. Alternative and nonexclusive interpretations are that the emission results from a population of millisecond pulsars dispersed in the bulge and disk of M31 by disrupted globular clusters or from the decay or annihilation of dark matter particles, similar to what has been proposed to account for the so-called Galactic center excess found in Fermi-LAT observations of the MW. |
| 学科主题 | 天文学 |
| WOS标题词 | Science & Technology ; Physical Sciences |
| 类目[WOS] | Astronomy & Astrophysics |
| 研究领域[WOS] | Astronomy & Astrophysics |
| 关键词[WOS] | LARGE-MAGELLANIC-CLOUD ; STAR-FORMING GALAXIES ; GAMMA-RAY EMISSION ; LOCAL GROUP GALAXIES ; HERSCHEL EXPLOITATION ; GLOBULAR-CLUSTERS ; STELLAR MASS ; DARK-MATTER ; COSMIC-RAYS ; ATOMIC GAS |
| 收录类别 | SCI |
| 原文出处 | http://stacks.iop.org/0004-637X/836/i=2/a=208?key=crossref.d3a26516c1fa7f0976606b33c5c5a84a |
| 语种 | 英语 |
| WOS记录号 | WOS:000395870900001 |
| 源URL | [http://ir.ynao.ac.cn/handle/114a53/9985]  |
| 专题 | 云南天文台_高能天体物理研究组 云南天文台_中国科学院天体结构与演化重点实验室 |
| 作者单位 | 1.Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen, Germany 2.Department of Physics and Astronomy, Clemson University, Kinard Lab of Physics, Clemson, SC 29634, USA 3.Los Alamos National Laboratory, Los Alamos, NM 87545, USA 4.Università di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa I-56127 Pisa, Italy 5.Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d’Astrophysique, CEA Saclay, F-91191 Gif sur Yvette, France 6.Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste, Italy 7.Dipartimento di Fisica, Università di Trieste, I-34127 Trieste, Italy 8.Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova, Italy 9.Dipartimento di Fisica e Astronomia “G. Galilei,” Università di Padova, I-35131 Padova, Italy 10.Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa, Italy |
| 推荐引用方式 GB/T 7714 | Ackermann, M.,Ajello, M.,Albert, A.,et al. Observations of M31 and M33 with the Fermi Large Area Telescope: A Galactic Center Excess in Andromeda?[J]. ASTROPHYSICAL JOURNAL,2017,836(2). |
| APA | Ackermann, M..,Ajello, M..,Albert, A..,Baldini, L..,Ballet, J..,...&Zhou M.(2017).Observations of M31 and M33 with the Fermi Large Area Telescope: A Galactic Center Excess in Andromeda?.ASTROPHYSICAL JOURNAL,836(2). |
| MLA | Ackermann, M.,et al."Observations of M31 and M33 with the Fermi Large Area Telescope: A Galactic Center Excess in Andromeda?".ASTROPHYSICAL JOURNAL 836.2(2017). |
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来源：云南天文台
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