DETERMINATION OF THE POINT-SPREAD FUNCTION FOR THE FERMI LARGE AREA TELESCOPE FROM ON-ORBIT DATA AND LIMITS ON PAIR HALOS OF ACTIVE GALACTIC NUCLEI
DETERMINATION OF THE POINT-SPREAD FUNCTION FOR THE FERMI LARGE AREA TELESCOPE FROM ON-ORBIT DATA AND LIMITS ON PAIR HALOS OF ACTIVE GALACTIC NUCLEI
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DOI：
10.1088/0004-637x/765/1/54
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发表时间：
2013-03
期刊：
影响因子：
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通讯作者：
M. Ackermann;M. Ajello;A. Allafort;K. Asano;W. Atwood;L. Baldini;J. Ballet;G. Barbiellini;
中科院分区：
文献类型：
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作者：
M. Ackermann;M. Ajello;A. Allafort;K. Asano;W. Atwood;L. Baldini;J. Ballet;G. Barbiellini;
费米伽马射线太空望远镜上的大面积望远镜（LAT）是一个对转换望远镜，设计用于探测能量从1.20 MeV到>300 GeV的光子。LAT的发射前响应函数是通过大量的蒙特卡罗模拟和束流试验确定的。本文利用近两年的在轨观测数据，通过对来自活动星系核（AGN）和恒星的γ射线分布的分析，确定了表征重建光子角分布的点扩散函数（PSF），它是探测器能量和几何形状的函数。高于3 GeV，PSF被发现是更广泛的比发射前的PSF。我们检查了PSF对γ射线源类别和观测时期的依赖性，没有发现。我们还研究了BL Lac活动星系核周围成对晕辐射的几种可能的空间模型。我们没有发现空间延伸大于PSF的分量的证据，并在低和高红移BL Lac AGN和TeV耀变体1ES 0229 +200和1ES 0347 −121的堆叠图像中设置了晕发射幅度的上限。
The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to detect photons with energies from ≈20 MeV to >300 GeV. The pre-launch response functions of the LAT were determined through extensive Monte Carlo simulations and beam tests. The point-spread function (PSF) characterizing the angular distribution of reconstructed photons as a function of energy and geometry in the detector is determined here from two years of on-orbit data by examining the distributions of γ rays from pulsars and active galactic nuclei (AGNs). Above 3 GeV, the PSF is found to be broader than the pre-launch PSF. We checked for dependence of the PSF on the class of γ-ray source and observation epoch and found none. We also investigated several possible spatial models for pair-halo emission around BL Lac AGNs. We found no evidence for a component with spatial extension larger than the PSF and set upper limits on the amplitude of halo emission in stacked images of low- and high-redshift BL Lac AGNs and the TeV blazars 1ES0229+200 and 1ES0347−121.