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

Ackermann, M; Ajello, M; Allafort, A; Asano, K; Atwood, Wb; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Bloom, Ed; Bonamente, E; Borgland, Aw; Bottacini, E; Brandt, Tj; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Burnett, Th; Busetto, G; Buson, S; Caliandro, Ga; Cameron, Ra; Caraveo, Pa; Casandjian, Jm; Cecchi, C; Charles, E; Chaty, S; Chekhtman, A; Cheung, Cc; Chiang, J; Cillis, An; Ciprini, S; Claus, R; Cohen Tanugi, J; Colafrancesco, S; Conrad, J; Cutini, S; D'Ammando, F; de Palma, F; Dermer, Cd; Ede, Silva; Drell, S; Drlica Wagner, A; Dubois, R; Favuzzi, Cecilia; Fegan, Sj; Ferrara, Ec; Focke, Wb; Fortin, P; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, Nicola; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grandi, P; Grenier, Ia; Grove, Je; Guiriec, S; Hadasch, D; Hayashida, M; Hays, E; Horan, D; Hou, X; Hughes, Re; Jackson, Ms; Jogler, T; Johannesson, G; Johnson, Rp; Johnson, As; Kamae, T; Kataoka, J; Kerr, M; Knodlseder, J; Kuss, M; Lande, J; Larsson, S; Latronico, L; Lavalley, C; Lee, Sh; Longo, F; Loparco, F; Lott, B; Lovellette, Mn; Lubrano, P; Mazziotta, Mn; Mcconville, W; Mcenery, Je; Mehault, J; Michelson, Pf; Mignani, Rp; Mitthumsiri, W; Mizuno, T; Moiseev, Aa; Monte, C; Monzani, Me; Morselli, A; Moskalenko, Iv; Murgia, S; Naumann Godo, M; Nemmen, R; Nishino, S; Norris, Jp; Nuss, E; Ohsugi, T; Omodei, N; Orienti, M; Orlando, E; Ormes, Jf; Paneque, D; Panetta, Jh; Pelassa, V; Perkins, Js; Pesce Rollins, M; Pierbattista, M; Piron, F; Pivato, G; Poon, H; Porter, Ta; Raino, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Reyes, Lc; Ritz, S; Rochester, Ls; Romoli, C; Roth, M; Sanchez, Da; Pms, Parkinson; Scargle, Jd; Sgro, C; Siskind, Ej; Snyder, A; Spandre, G; Spinelli, P; Stephens, Te; Suson, Dj; Tajima, H; Takahashi, H; Tanaka, T; Thayer, Jg; Thayer, Jb; Thompson, Dj; Tibaldo, L; Tibolla, O; Tinivella, M; Tosti, G; Troja, E; Usher, Tl; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; von Kienlin, A; Waite, Ap; Wallace, E; Weltevrede, P; Winer, Bl; Wood, Ks; Wood, M; Yang, Z; Zimmer, S.

doi:10.1088/0004-637X/765/1/54

The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to detect photons with energies from approximate to 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 gamma 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 gamma-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.

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 / Ackermann, M; Ajello, M; Allafort, A; Asano, K; Atwood, Wb; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Bloom, Ed; Bonamente, E; Borgland, Aw; Bottacini, E; Brandt, Tj; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Burnett, Th; Busetto, G; Buson, S; Caliandro, Ga; Cameron, Ra; Caraveo, Pa; Casandjian, Jm; Cecchi, C; Charles, E; Chaty, S; Chekhtman, A; Cheung, Cc; Chiang, J; Cillis, An; Ciprini, S; Claus, R; Cohen Tanugi, J; Colafrancesco, S; Conrad, J; Cutini, S; D'Ammando, F; de Palma, F; Dermer, Cd; Silva, Ede; Drell, S; Drlica Wagner, A; Dubois, R; Favuzzi, Cecilia; Fegan, Sj; Ferrara, Ec; Focke, Wb; Fortin, P; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, Nicola; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grandi, P; Grenier, Ia; Grove, Je; Guiriec, S; Hadasch, D; Hayashida, M; Hays, E; Horan, D; Hou, X; Hughes, Re; Jackson, Ms; Jogler, T; Johannesson, G; Johnson, Rp; Johnson, As; Kamae, T; Kataoka, J; Kerr, M; Knodlseder, J; Kuss, M; Lande, J; Larsson, S; Latronico, L; Lavalley, C; Lee, Sh; Longo, F; Loparco, F; Lott, B; Lovellette, Mn; Lubrano, P; Mazziotta, Mn; Mcconville, W; Mcenery, Je; Mehault, J; Michelson, Pf; Mignani, Rp; Mitthumsiri, W; Mizuno, T; Moiseev, Aa; Monte, C; Monzani, Me; Morselli, A; Moskalenko, Iv; Murgia, S; Naumann Godo, M; Nemmen, R; Nishino, S; Norris, Jp; Nuss, E; Ohsugi, T; Omodei, N; Orienti, M; Orlando, E; Ormes, Jf; Paneque, D; Panetta, Jh; Pelassa, V; Perkins, Js; Pesce Rollins, M; Pierbattista, M; Piron, F; Pivato, G; Poon, H; Porter, Ta; Raino, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Reyes, Lc; Ritz, S; Rochester, Ls; Romoli, C; Roth, M; Sanchez, Da; Parkinson, Pms; Scargle, Jd; Sgro, C; Siskind, Ej; Snyder, A; Spandre, G; Spinelli, P; Stephens, Te; Suson, Dj; Tajima, H; Takahashi, H; Tanaka, T; Thayer, Jg; Thayer, Jb; Thompson, Dj; Tibaldo, L; Tibolla, O; Tinivella, M; Tosti, G; Troja, E; Usher, Tl; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; von Kienlin, A; Waite, Ap; Wallace, E; Weltevrede, P; Winer, Bl; Wood, Ks; Wood, M; Yang, Z; Zimmer, S.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 765:1(2013). [10.1088/0004-637X/765/1/54]