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

M. Ackermann, M. Ajello, A. Allafort, K. Asano, W. B. Atwood, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, E. D. Bloom, E. Bonamente, A. W. Borgland, E. Bottacini, T. J. Brandt, J. Bregeon, M. Brigida, P. Bruel, R. Buehler & 154 others T. H. Burnett, G. Busetto, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, J. M. Casandjian, C. Cecchi, E. Charles, S. Chaty, A. Chekhtman, C. C. Cheung, J. Chiang, A. N. Cillis, S. Ciprini, R. Claus, J. Cohen-Tanugi, S. Colafrancesco, J. Conrad, S. Cutini, F. D'Ammando, F. De Palma, C. D. Dermer, E. Do Couto E Silva, P. S. Drell, A. Drlica-Wagner, R. Dubois, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, P. Fortin, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Gehrels, S. Germani, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, P. Grandi, I. A. Grenier, J. E. Grove, S. Guiriec, D. Hadasch, M. Hayashida, E. Hays, D. Horan, X. Hou, R. E. Hughes, M. S. Jackson, T. Jogler, G. Jóhannesson, R. P. Johnson, A. S. Johnson, T. Kamae, Jun Kataoka, M. Kerr, J. Knödlseder, M. Kuss, J. Lande, S. Larsson, L. Latronico, C. Lavalley, S. H. Lee, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, M. N. Mazziotta, W. McConville, J. E. McEnery, J. Mehault, P. F. Michelson, R. P. Mignani, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, M. Naumann-Godo, R. Nemmen, S. Nishino, J. P. Norris, E. Nuss, T. Ohsugi, N. Omodei, M. Orienti, E. Orlando, J. F. Ormes, D. Paneque, J. H. Panetta, V. Pelassa, J. S. Perkins, M. Pesce-Rollins, M. Pierbattista, F. Piron, G. Pivato, H. Poon, T. A. Porter, S. Rainò, R. Rando, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, L. C. Reyes, S. Ritz, L. S. Rochester, C. Romoli, M. Roth, D. A. Sanchez, P. M. Saz Parkinson, J. D. Scargle, C. Sgrò, E. J. Siskind, A. Snyder, G. Spandre, P. Spinelli, T. E. Stephens, D. J. Suson, H. Tajima, H. Takahashi, T. Tanaka, J. G. Thayer, J. B. Thayer, D. J. Thompson, L. Tibaldo, O. Tibolla, M. Tinivella, G. Tosti, E. Troja, T. L. Usher, J. Vandenbroucke, V. Vasileiou, G. Vianello, V. Vitale, A. Von Kienlin, A. P. Waite, E. Wallace, P. Weltevrede, B. L. Winer, K. S. Wood, M. Wood, Z. Yang, S. Zimmer

    Research output: Contribution to journalArticle

    46 Citations (Scopus)

    Abstract

    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.

    Original languageEnglish
    Article number54
    JournalAstrophysical Journal
    Volume765
    Issue number1
    DOIs
    Publication statusPublished - 2013 Mar 1

    Fingerprint

    point spread functions
    active galactic nuclei
    halos
    telescopes
    orbits
    energy
    rays
    geometry
    Fermi Gamma-ray Space Telescope
    blazars
    simulation
    photons
    pulsars
    angular distribution
    time measurement
    distribution
    detectors
    detector
    test

    Keywords

    • galaxies: active
    • galaxies: halos
    • gamma rays: galaxies
    • instrumentation: detectors
    • intergalactic medium

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    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, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Burnett, T. H.; Busetto, G.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Charles, E.; Chaty, S.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Cillis, A. N.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Colafrancesco, S.; Conrad, J.; Cutini, S.; D'Ammando, F.; De Palma, F.; Dermer, C. D.; Do Couto E Silva, E.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fortin, P.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grandi, P.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hays, E.; Horan, D.; Hou, X.; Hughes, R. E.; Jackson, M. S.; Jogler, T.; Jóhannesson, G.; Johnson, R. P.; Johnson, A. S.; Kamae, T.; Kataoka, Jun; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Lavalley, C.; Lee, S. H.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; McConville, W.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mignani, R. P.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Nemmen, R.; Nishino, S.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Pelassa, V.; Perkins, J. S.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Poon, H.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Reyes, L. C.; Ritz, S.; Rochester, L. S.; Romoli, C.; Roth, M.; Sanchez, D. A.; Saz Parkinson, P. M.; Scargle, J. D.; Sgrò, C.; Siskind, E. J.; Snyder, A.; Spandre, G.; Spinelli, P.; Stephens, T. E.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tibolla, O.; Tinivella, M.; Tosti, G.; Troja, E.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Von Kienlin, A.; Waite, A. P.; Wallace, E.; Weltevrede, P.; Winer, B. L.; Wood, K. S.; Wood, M.; Yang, Z.; Zimmer, S.

    In: Astrophysical Journal, Vol. 765, No. 1, 54, 01.03.2013.

    Research output: Contribution to journalArticle

    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, Do Couto E Silva, E, Drell, PS, Drlica-Wagner, A, Dubois, R, Favuzzi, C, Fegan, SJ, Ferrara, EC, Focke, WB, Fortin, P, Fukazawa, Y, Funk, S, Fusco, P, Gargano, F, Gasparrini, D, Gehrels, N, Germani, S, Giglietto, N, 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, Jóhannesson, G, Johnson, RP, Johnson, AS, Kamae, T, Kataoka, J, Kerr, M, Knödlseder, 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, Rainò, S, Rando, R, Razzano, M, Razzaque, S, Reimer, A, Reimer, O, Reyes, LC, Ritz, S, Rochester, LS, Romoli, C, Roth, M, Sanchez, DA, Saz Parkinson, PM, Scargle, JD, Sgrò, 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 2013, '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', Astrophysical Journal, vol. 765, no. 1, 54. https://doi.org/10.1088/0004-637X/765/1/54
    Ackermann, M. ; Ajello, M. ; Allafort, A. ; Asano, K. ; Atwood, W. B. ; Baldini, L. ; Ballet, J. ; Barbiellini, G. ; Bastieri, D. ; Bechtol, K. ; Bellazzini, R. ; Bloom, E. D. ; Bonamente, E. ; Borgland, A. W. ; Bottacini, E. ; Brandt, T. J. ; Bregeon, J. ; Brigida, M. ; Bruel, P. ; Buehler, R. ; Burnett, T. H. ; Busetto, G. ; Buson, S. ; Caliandro, G. A. ; Cameron, R. A. ; Caraveo, P. A. ; Casandjian, J. M. ; Cecchi, C. ; Charles, E. ; Chaty, S. ; Chekhtman, A. ; Cheung, C. C. ; Chiang, J. ; Cillis, A. N. ; Ciprini, S. ; Claus, R. ; Cohen-Tanugi, J. ; Colafrancesco, S. ; Conrad, J. ; Cutini, S. ; D'Ammando, F. ; De Palma, F. ; Dermer, C. D. ; Do Couto E Silva, E. ; Drell, P. S. ; Drlica-Wagner, A. ; Dubois, R. ; Favuzzi, C. ; Fegan, S. J. ; Ferrara, E. C. ; Focke, W. B. ; Fortin, P. ; Fukazawa, Y. ; Funk, S. ; Fusco, P. ; Gargano, F. ; Gasparrini, D. ; Gehrels, N. ; Germani, S. ; Giglietto, N. ; Giordano, F. ; Giroletti, M. ; Glanzman, T. ; Godfrey, G. ; Grandi, P. ; Grenier, I. A. ; Grove, J. E. ; Guiriec, S. ; Hadasch, D. ; Hayashida, M. ; Hays, E. ; Horan, D. ; Hou, X. ; Hughes, R. E. ; Jackson, M. S. ; Jogler, T. ; Jóhannesson, G. ; Johnson, R. P. ; Johnson, A. S. ; Kamae, T. ; Kataoka, Jun ; Kerr, M. ; Knödlseder, J. ; Kuss, M. ; Lande, J. ; Larsson, S. ; Latronico, L. ; Lavalley, C. ; Lee, S. H. ; Longo, F. ; Loparco, F. ; Lott, B. ; Lovellette, M. N. ; Lubrano, P. ; Mazziotta, M. N. ; McConville, W. ; McEnery, J. E. ; Mehault, J. ; Michelson, P. F. ; Mignani, R. P. ; Mitthumsiri, W. ; Mizuno, T. ; Moiseev, A. A. ; Monte, C. ; Monzani, M. E. ; Morselli, A. ; Moskalenko, I. V. ; Murgia, S. ; Naumann-Godo, M. ; Nemmen, R. ; Nishino, S. ; Norris, J. P. ; Nuss, E. ; Ohsugi, T. ; Omodei, N. ; Orienti, M. ; Orlando, E. ; Ormes, J. F. ; Paneque, D. ; Panetta, J. H. ; Pelassa, V. ; Perkins, J. S. ; Pesce-Rollins, M. ; Pierbattista, M. ; Piron, F. ; Pivato, G. ; Poon, H. ; Porter, T. A. ; Rainò, S. ; Rando, R. ; Razzano, M. ; Razzaque, S. ; Reimer, A. ; Reimer, O. ; Reyes, L. C. ; Ritz, S. ; Rochester, L. S. ; Romoli, C. ; Roth, M. ; Sanchez, D. A. ; Saz Parkinson, P. M. ; Scargle, J. D. ; Sgrò, C. ; Siskind, E. J. ; Snyder, A. ; Spandre, G. ; Spinelli, P. ; Stephens, T. E. ; Suson, D. J. ; Tajima, H. ; Takahashi, H. ; Tanaka, T. ; Thayer, J. G. ; Thayer, J. B. ; Thompson, D. J. ; Tibaldo, L. ; Tibolla, O. ; Tinivella, M. ; Tosti, G. ; Troja, E. ; Usher, T. L. ; Vandenbroucke, J. ; Vasileiou, V. ; Vianello, G. ; Vitale, V. ; Von Kienlin, A. ; Waite, A. P. ; Wallace, E. ; Weltevrede, P. ; Winer, B. L. ; Wood, K. S. ; Wood, M. ; Yang, Z. ; Zimmer, S. / 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. In: Astrophysical Journal. 2013 ; Vol. 765, No. 1.
    @article{dae5c8195952421b858ae99cbf7aea44,
    title = "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",
    abstract = "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.",
    keywords = "galaxies: active, galaxies: halos, gamma rays: galaxies, instrumentation: detectors, intergalactic medium",
    author = "M. Ackermann and M. Ajello and A. Allafort and K. Asano and Atwood, {W. B.} and L. Baldini and J. Ballet and G. Barbiellini and D. Bastieri and K. Bechtol and R. Bellazzini and Bloom, {E. D.} and E. Bonamente and Borgland, {A. W.} and E. Bottacini and Brandt, {T. J.} and J. Bregeon and M. Brigida and P. Bruel and R. Buehler and Burnett, {T. H.} and G. Busetto and S. Buson and Caliandro, {G. A.} and Cameron, {R. A.} and Caraveo, {P. A.} and Casandjian, {J. M.} and C. Cecchi and E. Charles and S. Chaty and A. Chekhtman and Cheung, {C. C.} and J. Chiang and Cillis, {A. N.} and S. Ciprini and R. Claus and J. Cohen-Tanugi and S. Colafrancesco and J. Conrad and S. Cutini and F. D'Ammando and {De Palma}, F. and Dermer, {C. D.} and {Do Couto E Silva}, E. and Drell, {P. S.} and A. Drlica-Wagner and R. Dubois and C. Favuzzi and Fegan, {S. J.} and Ferrara, {E. C.} and Focke, {W. B.} and P. Fortin and Y. Fukazawa and S. Funk and P. Fusco and F. Gargano and D. Gasparrini and N. Gehrels and S. Germani and N. Giglietto and F. Giordano and M. Giroletti and T. Glanzman and G. Godfrey and P. Grandi and Grenier, {I. A.} and Grove, {J. E.} and S. Guiriec and D. Hadasch and M. Hayashida and E. Hays and D. Horan and X. Hou and Hughes, {R. E.} and Jackson, {M. S.} and T. Jogler and G. J{\'o}hannesson and Johnson, {R. P.} and Johnson, {A. S.} and T. Kamae and Jun Kataoka and M. Kerr and J. Kn{\"o}dlseder and M. Kuss and J. Lande and S. Larsson and L. Latronico and C. Lavalley and Lee, {S. H.} and F. Longo and F. Loparco and B. Lott and Lovellette, {M. N.} and P. Lubrano and Mazziotta, {M. N.} and W. McConville and McEnery, {J. E.} and J. Mehault and Michelson, {P. F.} and Mignani, {R. P.} and W. Mitthumsiri and T. Mizuno and Moiseev, {A. A.} and C. Monte and Monzani, {M. E.} and A. Morselli and Moskalenko, {I. V.} and S. Murgia and M. Naumann-Godo and R. Nemmen and S. Nishino and Norris, {J. P.} and E. Nuss and T. Ohsugi and N. Omodei and M. Orienti and E. Orlando and Ormes, {J. F.} and D. Paneque and Panetta, {J. H.} and V. Pelassa and Perkins, {J. S.} and M. Pesce-Rollins and M. Pierbattista and F. Piron and G. Pivato and H. Poon and Porter, {T. A.} and S. Rain{\`o} and R. Rando and M. Razzano and S. Razzaque and A. Reimer and O. Reimer and Reyes, {L. C.} and S. Ritz and Rochester, {L. S.} and C. Romoli and M. Roth and Sanchez, {D. A.} and {Saz Parkinson}, {P. M.} and Scargle, {J. D.} and C. Sgr{\`o} and Siskind, {E. J.} and A. Snyder and G. Spandre and P. Spinelli and Stephens, {T. E.} and Suson, {D. J.} and H. Tajima and H. Takahashi and T. Tanaka and Thayer, {J. G.} and Thayer, {J. B.} and Thompson, {D. J.} and L. Tibaldo and O. Tibolla and M. Tinivella and G. Tosti and E. Troja and Usher, {T. L.} and J. Vandenbroucke and V. Vasileiou and G. Vianello and V. Vitale and {Von Kienlin}, A. and Waite, {A. P.} and E. Wallace and P. Weltevrede and Winer, {B. L.} and Wood, {K. S.} and M. Wood and Z. Yang and S. Zimmer",
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    doi = "10.1088/0004-637X/765/1/54",
    language = "English",
    volume = "765",
    journal = "Astrophysical Journal",
    issn = "0004-637X",
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    TY - JOUR

    T1 - 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

    AU - Ackermann, M.

    AU - Ajello, M.

    AU - Allafort, A.

    AU - Asano, K.

    AU - Atwood, W. B.

    AU - Baldini, L.

    AU - Ballet, J.

    AU - Barbiellini, G.

    AU - Bastieri, D.

    AU - Bechtol, K.

    AU - Bellazzini, R.

    AU - Bloom, E. D.

    AU - Bonamente, E.

    AU - Borgland, A. W.

    AU - Bottacini, E.

    AU - Brandt, T. J.

    AU - Bregeon, J.

    AU - Brigida, M.

    AU - Bruel, P.

    AU - Buehler, R.

    AU - Burnett, T. H.

    AU - Busetto, G.

    AU - Buson, S.

    AU - Caliandro, G. A.

    AU - Cameron, R. A.

    AU - Caraveo, P. A.

    AU - Casandjian, J. M.

    AU - Cecchi, C.

    AU - Charles, E.

    AU - Chaty, S.

    AU - Chekhtman, A.

    AU - Cheung, C. C.

    AU - Chiang, J.

    AU - Cillis, A. N.

    AU - Ciprini, S.

    AU - Claus, R.

    AU - Cohen-Tanugi, J.

    AU - Colafrancesco, S.

    AU - Conrad, J.

    AU - Cutini, S.

    AU - D'Ammando, F.

    AU - De Palma, F.

    AU - Dermer, C. D.

    AU - Do Couto E Silva, E.

    AU - Drell, P. S.

    AU - Drlica-Wagner, A.

    AU - Dubois, R.

    AU - Favuzzi, C.

    AU - Fegan, S. J.

    AU - Ferrara, E. C.

    AU - Focke, W. B.

    AU - Fortin, P.

    AU - Fukazawa, Y.

    AU - Funk, S.

    AU - Fusco, P.

    AU - Gargano, F.

    AU - Gasparrini, D.

    AU - Gehrels, N.

    AU - Germani, S.

    AU - Giglietto, N.

    AU - Giordano, F.

    AU - Giroletti, M.

    AU - Glanzman, T.

    AU - Godfrey, G.

    AU - Grandi, P.

    AU - Grenier, I. A.

    AU - Grove, J. E.

    AU - Guiriec, S.

    AU - Hadasch, D.

    AU - Hayashida, M.

    AU - Hays, E.

    AU - Horan, D.

    AU - Hou, X.

    AU - Hughes, R. E.

    AU - Jackson, M. S.

    AU - Jogler, T.

    AU - Jóhannesson, G.

    AU - Johnson, R. P.

    AU - Johnson, A. S.

    AU - Kamae, T.

    AU - Kataoka, Jun

    AU - Kerr, M.

    AU - Knödlseder, J.

    AU - Kuss, M.

    AU - Lande, J.

    AU - Larsson, S.

    AU - Latronico, L.

    AU - Lavalley, C.

    AU - Lee, S. H.

    AU - Longo, F.

    AU - Loparco, F.

    AU - Lott, B.

    AU - Lovellette, M. N.

    AU - Lubrano, P.

    AU - Mazziotta, M. N.

    AU - McConville, W.

    AU - McEnery, J. E.

    AU - Mehault, J.

    AU - Michelson, P. F.

    AU - Mignani, R. P.

    AU - Mitthumsiri, W.

    AU - Mizuno, T.

    AU - Moiseev, A. A.

    AU - Monte, C.

    AU - Monzani, M. E.

    AU - Morselli, A.

    AU - Moskalenko, I. V.

    AU - Murgia, S.

    AU - Naumann-Godo, M.

    AU - Nemmen, R.

    AU - Nishino, S.

    AU - Norris, J. P.

    AU - Nuss, E.

    AU - Ohsugi, T.

    AU - Omodei, N.

    AU - Orienti, M.

    AU - Orlando, E.

    AU - Ormes, J. F.

    AU - Paneque, D.

    AU - Panetta, J. H.

    AU - Pelassa, V.

    AU - Perkins, J. S.

    AU - Pesce-Rollins, M.

    AU - Pierbattista, M.

    AU - Piron, F.

    AU - Pivato, G.

    AU - Poon, H.

    AU - Porter, T. A.

    AU - Rainò, S.

    AU - Rando, R.

    AU - Razzano, M.

    AU - Razzaque, S.

    AU - Reimer, A.

    AU - Reimer, O.

    AU - Reyes, L. C.

    AU - Ritz, S.

    AU - Rochester, L. S.

    AU - Romoli, C.

    AU - Roth, M.

    AU - Sanchez, D. A.

    AU - Saz Parkinson, P. M.

    AU - Scargle, J. D.

    AU - Sgrò, C.

    AU - Siskind, E. J.

    AU - Snyder, A.

    AU - Spandre, G.

    AU - Spinelli, P.

    AU - Stephens, T. E.

    AU - Suson, D. J.

    AU - Tajima, H.

    AU - Takahashi, H.

    AU - Tanaka, T.

    AU - Thayer, J. G.

    AU - Thayer, J. B.

    AU - Thompson, D. J.

    AU - Tibaldo, L.

    AU - Tibolla, O.

    AU - Tinivella, M.

    AU - Tosti, G.

    AU - Troja, E.

    AU - Usher, T. L.

    AU - Vandenbroucke, J.

    AU - Vasileiou, V.

    AU - Vianello, G.

    AU - Vitale, V.

    AU - Von Kienlin, A.

    AU - Waite, A. P.

    AU - Wallace, E.

    AU - Weltevrede, P.

    AU - Winer, B. L.

    AU - Wood, K. S.

    AU - Wood, M.

    AU - Yang, Z.

    AU - Zimmer, S.

    PY - 2013/3/1

    Y1 - 2013/3/1

    N2 - 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.

    AB - 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.

    KW - galaxies: active

    KW - galaxies: halos

    KW - gamma rays: galaxies

    KW - instrumentation: detectors

    KW - intergalactic medium

    UR - http://www.scopus.com/inward/record.url?scp=84874122100&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=84874122100&partnerID=8YFLogxK

    U2 - 10.1088/0004-637X/765/1/54

    DO - 10.1088/0004-637X/765/1/54

    M3 - Article

    VL - 765

    JO - Astrophysical Journal

    JF - Astrophysical Journal

    SN - 0004-637X

    IS - 1

    M1 - 54

    ER -