Exploring the nature of Galactic unassociated sources detected by the Fermi-LAT
探索Fermi-LAT探测到的银河系未关联源的性质
F. Acero, A. Acharyya, A. Adelfio, M. Ajello, E. Aviano, L. Baldini, J. Ballet, C. Bartolini, D. Bastieri, J. Becerra Gonzalez, R. Bellazzini, A. Bhat, E. Bissaldi, R. Bonino, P. Bruel, R. A. Cameron, P. A. Caraveo, F. Casaburo, F. Casini, E. Cavazzuti, N. Cibrario, S. Ciprini, G. Cozzolongo, P. Cristarella Orestano, F. Cuna, S. Cutini, F. D'Ammando, P. de la Torre Luque, D. Depalo, N. Di Lalla, A. Dinesh, L. Di Venere, A. Dominguez, J. Eagle, C. Fernandez-Suarez, A. Fiori, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, C. Gasbarra, D. Gasparrini, S. Germani, F. Giacchino, N. Giglietto, M. Giliberti, F. Giordano, M. Giroletti, I. A. Grenier, M.-H. Grondin, S. Guiriec, R. Gupta, M. Hashizume, E. Hays, J.W. Hewitt, A. Holzmann Airasca, D. Horan, X. Hou, T. Kayanoki, M. Kerr, M. Kuss, D.A. Langis, A. Laviron, M. Lemoine-Goumard, A. Liguori, J. Li, I. Liodakis, P. Loizzo, F. Longo, F. Loparco, S. Lopez Pérez, L. Lorusso, B. Lott, M. N. Lovellette, P. Lubrano, S. Maldera, D. Malyshev, G. Marti-Devesa, R. Martinelli, M. N. Mazziotta, I.Mereu, M. Michailidis, P. F. Michelson, T. Mizuno, P. Monti-Guarnieri, M. E. Monzani, A. Morselli, M. Negro, N. Omodei, M. Orienti, E. Orlando, D. Paneque, G. Panzarini, M. Persic, M. Pesce-Rollins, R. Pillera, T. A. Porter, G. Principe, S. Raino, R. Rando
AI总结 利用机器学习分类和蒙特卡洛模拟,研究Fermi-LAT在银道面附近探测到的未关联源,发现其具有陡峭弯曲谱和特殊纬度分布,可能源于弥散发射的误建模或新类型伽马射线源。
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- Accepted for publication in the Astrophysical Journal Supplement. Data posted at this https URL (https://zenodo.org/records/20342245)
我们研究了Fermi-LAT在银道面附近(|b|<10°)探测到的未关联源的性质,这些源占4FGL-DR4星表中所有源的16%。这些源(称为软银河未关联源,SGUs)表现出已知伽马射线源类别中未发现的性质,这一点通过机器学习分类方法得到证实。具体而言,这些性质包括在1 GeV以下达到峰值的陡峭弯曲谱,以及具有窄分量和宽分量(分别称为尖峰和肩峰)的特定银纬分布。我们突出显示了一些源团。探索了新的可能源类别,但只有恒星形成区被发现占未关联源群体的显著比例(最多10%)。对175个最亮源对应体的彻底搜索发现了一些可能的对应体,但未揭示整个群体的性质线索。我们研究了SGUs起源于弥散发射误建模团块的可能性。使用蒙特卡洛模拟,在关于团块空间延伸的特定条件下,可以重现SGU谱。利用13CO MOPRA数据探索了SGUs与12CO示踪剂未计及的气体之间的可能联系,但结果不明确。SGUs起源于弥散发射的可能性仍然存在。然而,SGUs代表一类新的伽马射线源的场景也不能完全排除。
We investigate the nature of the unassociated sources detected by the Fermi-LAT close (|b|<10°) to the Galactic plane, representing 16% of all sources in the 4FGL-DR4 catalog. The bulk of these sources (referred to as soft Galactic unassociated sources, SGUs) exhibit properties not found in known classes of gamma-ray emitters, as confirmed by a machine-learning classification approach. In particular, these properties include a steep, curved spectrum peaking below 1 GeV and a specific Galactic-latitude distribution with both a narrow and a broad component (dubbed the spike and the shoulder, respectively). Some source clusters are highlighted. New plausible source classes are explored, but only star-forming regions are found to account for a significant fraction (at most 10%) of the unassociated population. A thorough search for counterparts to the 175 brightest sources brings out a number of plausible counterparts but does not reveal clues about the nature of the whole population. We investigate the possibility that SGUs originate from mismodeled clumps of diffuse emission. Using Monte Carlo simulations, the SGU spectra can be reproduced in this scenario under an ad hoc condition concerning the clump spatial extension. The possible connection between the SGUs and gas not accounted for by the 12CO tracer is explored using the 13CO MOPRA data but leads to inconclusive results. The origin of SGUs being related to diffuse emission remains plausible. However, a scenario whereby SGUs represent a new class of gamma-ray emitters cannot be fully excluded.