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; 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; J. 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

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

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. BuehlerT. 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, J. 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 journal › Article › peer-review

68 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 language	English
Article number	54
Journal	Astrophysical Journal
Volume	765
Issue number	1
DOIs	https://doi.org/10.1088/0004-637X/765/1/54
Publication status	Published - 1 Mar 2013
Externally published	Yes

Keywords

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

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

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

Cite this

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., ... 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, 765(1), Article 54. https://doi.org/10.1088/0004-637X/765/1/54

@article{472c50a14ac5496eb76044bd2fdd98c0,

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 J. 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",

year = "2013",

month = mar,

day = "1",

doi = "10.1088/0004-637X/765/1/54",

language = "English",

volume = "765",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "American Astronomical Society",

number = "1",

}

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

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, J.

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

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

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

M3 - Article

AN - SCOPUS:84874122100

SN - 0004-637X

VL - 765

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1

M1 - 54

ER -

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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