The cosmic-ray and gas content of the Cygnus region as measured in γ-rays by the Fermi Large Area Telescope

M. Ackermann, M. Ajello, A. Allafort, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, A. Belfiore, R. Bellazzini, B. Berenji, R. D. Blandford, E. D. Bloom, E. Bonamente, A. W. Borgland, E. Bottacini, J. Bregeon, M. Brigida, P. Bruel, R. Buehler, S. BusonG. A. Caliandro, R. A. Cameron, P. A. Caraveo, J. M. Casandjian, C. Cecchi, A. Chekhtman, S. Ciprini, R. Claus, J. Cohen-Tanugi, A. De Angelis, F. De Palma, C. D. Dermer, E. Do Couto E Silva, P. S. Drell, D. Dumora, C. Favuzzi, S. J. Fegan, W. B. Focke, P. Fortin, Y. Fukazawa, P. Fusco, F. Gargano, S. Germani, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, I. A. Grenier, L. Guillemot, S. Guiriec, D. Hadasch, Y. Hanabata, A. K. Harding, M. Hayashida, K. Hayashi, E. Hays, G. Jóhannesson, A. S. Johnson, T. Kamae, H. Katagiri, Jun Kataoka, M. Kerr, J. Knödlseder, M. Kuss, J. Lande, L. Latronico, S. H. Lee, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, P. Martin, M. N. Mazziotta, J. E. McEnery, J. Mehault, P. F. Michelson, W. Mitthumsiri, T. Mizuno, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, M. Naumann-Godo, P. L. Nolan, J. P. Norris, E. Nuss, T. Ohsugi, A. Okumura, N. Omodei, E. Orlando, J. F. Ormes, M. Ozaki, D. Paneque, D. Parent, M. Pesce-Rollins, M. Pierbattista, F. Piron, T. A. Porter, S. Rainò, R. Rando, M. Razzano, O. Reimer, T. Reposeur, S. Ritz, P. M. Saz Parkinson, C. Sgrò, E. J. Siskind, P. D. Smith, P. Spinelli, A. W. Strong, H. Takahashi, T. Tanaka, J. G. Thayer, J. B. Thayer, D. J. Thompson, L. Tibaldo, D. F. Torres, G. Tosti, A. Tramacere, E. Troja, Y. Uchiyama, J. Vandenbroucke, V. Vasileiou, G. Vianello, V. Vitale, A. P. Waite, P. Wang, B. L. Winer, K. S. Wood, Z. Yang, S. Zimmer, S. Bontemps

    Research output: Contribution to journalArticle

    39 Citations (Scopus)

    Abstract

    Context. The Cygnus region hosts a giant molecular-cloud complex that actively forms massive stars. Interactions of cosmic rays with interstellar gas and radiation fields make it shine at γ-ray energies. Several γ-ray pulsars and other energetic sources are seen in this direction. Aims. In this paper we analyze the γ-ray emission measured by the Fermi Large Area Telescope (LAT) in the energy range from 100 MeV to 100 GeV in order to probe the gas and cosmic-ray content on the scale of the whole Cygnus complex. The γ-ray emission on the scale of the central massive stellar clusters and from individual sources is addressed elsewhere. Methods. The signal from bright pulsars is greatly reduced by selecting photons in their off-pulse phase intervals. We compare the diffuse γ-ray emission with interstellar gas maps derived from radio/mm-wave lines and visual extinction data. A general model of the region, including other pulsars and γ-ray sources, is sought. Results. The integral H i emissivity above 100 MeV averaged over the whole Cygnus complex amounts to [2.06 ± 0.11 (stat.) -0.84 +0.15(syst.)] × 10 -26 photons s -1 sr -1 H-atom -1, where the systematic error is dominated by the uncertainty on the H i opacity to calculate its column densities. The integral emissivity and its spectral energy distribution are both consistent within the systematics with LAT measurements in the interstellar space near the solar system. The average X CO = N(H 2)/W CO ratio is found to be [1.68 ± 0.05 (stat.) -0.10 +0.87(HI opacity)] × 10 20 molecules cm -2 (K km s -1) -1, consistent with other LAT measurements in the Local Arm. We detect significant γ-ray emission from dark neutral gas for a mass corresponding to ~40% of what is traced by CO. The total interstellar mass in the Cygnus complex inferred from its γ-ray emission amounts to 8 -1 +5 × 10 6 M at a distance of 1.4 kpc. Conclusions. Despite the conspicuous star formation activity and high masses of the interstellar clouds, the cosmic-ray population in the Cygnus complex averaged over a few hundred parsecs is similar to that of the local interstellar space.

    Original languageEnglish
    Article numberA71
    JournalAstronomy and Astrophysics
    Volume538
    DOIs
    Publication statusPublished - 2012

    Fingerprint

    cosmic gases
    cosmic ray
    cosmic rays
    rays
    telescopes
    gas
    emissivity
    pulsars
    interstellar space
    interstellar gas
    energy
    opacity
    radio wave
    solar system
    energetics
    extinction
    probe
    radio waves
    neutral gases
    photons

    Keywords

    • Cosmic rays
    • Gamma rays: ISM
    • ISM: abundances
    • ISM: clouds

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

    Cite this

    Ackermann, M., Ajello, M., Allafort, A., Baldini, L., Ballet, J., Barbiellini, G., ... Bontemps, S. (2012). The cosmic-ray and gas content of the Cygnus region as measured in γ-rays by the Fermi Large Area Telescope. Astronomy and Astrophysics, 538, [A71]. https://doi.org/10.1051/0004-6361/201117539

    The cosmic-ray and gas content of the Cygnus region as measured in γ-rays by the Fermi Large Area Telescope. / Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Belfiore, A.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Chekhtman, A.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; De Angelis, A.; De Palma, F.; Dermer, C. D.; Do Couto E Silva, E.; Drell, P. S.; Dumora, D.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Fortin, P.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Guillemot, L.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hayashi, K.; Hays, E.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Katagiri, H.; Kataoka, Jun; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S. H.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Martin, P.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Parent, D.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, O.; Reposeur, T.; Ritz, S.; Saz Parkinson, P. M.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spinelli, P.; Strong, A. W.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Troja, E.; Uchiyama, Y.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Zimmer, S.; Bontemps, S.

    In: Astronomy and Astrophysics, Vol. 538, A71, 2012.

    Research output: Contribution to journalArticle

    Ackermann, M, Ajello, M, Allafort, A, Baldini, L, Ballet, J, Barbiellini, G, Bastieri, D, Belfiore, A, Bellazzini, R, Berenji, B, Blandford, RD, Bloom, ED, Bonamente, E, Borgland, AW, Bottacini, E, Bregeon, J, Brigida, M, Bruel, P, Buehler, R, Buson, S, Caliandro, GA, Cameron, RA, Caraveo, PA, Casandjian, JM, Cecchi, C, Chekhtman, A, Ciprini, S, Claus, R, Cohen-Tanugi, J, De Angelis, A, De Palma, F, Dermer, CD, Do Couto E Silva, E, Drell, PS, Dumora, D, Favuzzi, C, Fegan, SJ, Focke, WB, Fortin, P, Fukazawa, Y, Fusco, P, Gargano, F, Germani, S, Giglietto, N, Giordano, F, Giroletti, M, Glanzman, T, Godfrey, G, Grenier, IA, Guillemot, L, Guiriec, S, Hadasch, D, Hanabata, Y, Harding, AK, Hayashida, M, Hayashi, K, Hays, E, Jóhannesson, G, Johnson, AS, Kamae, T, Katagiri, H, Kataoka, J, Kerr, M, Knödlseder, J, Kuss, M, Lande, J, Latronico, L, Lee, SH, Longo, F, Loparco, F, Lott, B, Lovellette, MN, Lubrano, P, Martin, P, Mazziotta, MN, McEnery, JE, Mehault, J, Michelson, PF, Mitthumsiri, W, Mizuno, T, Monte, C, Monzani, ME, Morselli, A, Moskalenko, IV, Murgia, S, Naumann-Godo, M, Nolan, PL, Norris, JP, Nuss, E, Ohsugi, T, Okumura, A, Omodei, N, Orlando, E, Ormes, JF, Ozaki, M, Paneque, D, Parent, D, Pesce-Rollins, M, Pierbattista, M, Piron, F, Porter, TA, Rainò, S, Rando, R, Razzano, M, Reimer, O, Reposeur, T, Ritz, S, Saz Parkinson, PM, Sgrò, C, Siskind, EJ, Smith, PD, Spinelli, P, Strong, AW, Takahashi, H, Tanaka, T, Thayer, JG, Thayer, JB, Thompson, DJ, Tibaldo, L, Torres, DF, Tosti, G, Tramacere, A, Troja, E, Uchiyama, Y, Vandenbroucke, J, Vasileiou, V, Vianello, G, Vitale, V, Waite, AP, Wang, P, Winer, BL, Wood, KS, Yang, Z, Zimmer, S & Bontemps, S 2012, 'The cosmic-ray and gas content of the Cygnus region as measured in γ-rays by the Fermi Large Area Telescope', Astronomy and Astrophysics, vol. 538, A71. https://doi.org/10.1051/0004-6361/201117539
    Ackermann, M. ; Ajello, M. ; Allafort, A. ; Baldini, L. ; Ballet, J. ; Barbiellini, G. ; Bastieri, D. ; Belfiore, A. ; Bellazzini, R. ; Berenji, B. ; Blandford, R. D. ; Bloom, E. D. ; Bonamente, E. ; Borgland, A. W. ; Bottacini, E. ; Bregeon, J. ; Brigida, M. ; Bruel, P. ; Buehler, R. ; Buson, S. ; Caliandro, G. A. ; Cameron, R. A. ; Caraveo, P. A. ; Casandjian, J. M. ; Cecchi, C. ; Chekhtman, A. ; Ciprini, S. ; Claus, R. ; Cohen-Tanugi, J. ; De Angelis, A. ; De Palma, F. ; Dermer, C. D. ; Do Couto E Silva, E. ; Drell, P. S. ; Dumora, D. ; Favuzzi, C. ; Fegan, S. J. ; Focke, W. B. ; Fortin, P. ; Fukazawa, Y. ; Fusco, P. ; Gargano, F. ; Germani, S. ; Giglietto, N. ; Giordano, F. ; Giroletti, M. ; Glanzman, T. ; Godfrey, G. ; Grenier, I. A. ; Guillemot, L. ; Guiriec, S. ; Hadasch, D. ; Hanabata, Y. ; Harding, A. K. ; Hayashida, M. ; Hayashi, K. ; Hays, E. ; Jóhannesson, G. ; Johnson, A. S. ; Kamae, T. ; Katagiri, H. ; Kataoka, Jun ; Kerr, M. ; Knödlseder, J. ; Kuss, M. ; Lande, J. ; Latronico, L. ; Lee, S. H. ; Longo, F. ; Loparco, F. ; Lott, B. ; Lovellette, M. N. ; Lubrano, P. ; Martin, P. ; Mazziotta, M. N. ; McEnery, J. E. ; Mehault, J. ; Michelson, P. F. ; Mitthumsiri, W. ; Mizuno, T. ; Monte, C. ; Monzani, M. E. ; Morselli, A. ; Moskalenko, I. V. ; Murgia, S. ; Naumann-Godo, M. ; Nolan, P. L. ; Norris, J. P. ; Nuss, E. ; Ohsugi, T. ; Okumura, A. ; Omodei, N. ; Orlando, E. ; Ormes, J. F. ; Ozaki, M. ; Paneque, D. ; Parent, D. ; Pesce-Rollins, M. ; Pierbattista, M. ; Piron, F. ; Porter, T. A. ; Rainò, S. ; Rando, R. ; Razzano, M. ; Reimer, O. ; Reposeur, T. ; Ritz, S. ; Saz Parkinson, P. M. ; Sgrò, C. ; Siskind, E. J. ; Smith, P. D. ; Spinelli, P. ; Strong, A. W. ; Takahashi, H. ; Tanaka, T. ; Thayer, J. G. ; Thayer, J. B. ; Thompson, D. J. ; Tibaldo, L. ; Torres, D. F. ; Tosti, G. ; Tramacere, A. ; Troja, E. ; Uchiyama, Y. ; Vandenbroucke, J. ; Vasileiou, V. ; Vianello, G. ; Vitale, V. ; Waite, A. P. ; Wang, P. ; Winer, B. L. ; Wood, K. S. ; Yang, Z. ; Zimmer, S. ; Bontemps, S. / The cosmic-ray and gas content of the Cygnus region as measured in γ-rays by the Fermi Large Area Telescope. In: Astronomy and Astrophysics. 2012 ; Vol. 538.
    @article{67d7c3d77fd6410bb8850a172910c9f7,
    title = "The cosmic-ray and gas content of the Cygnus region as measured in γ-rays by the Fermi Large Area Telescope",
    abstract = "Context. The Cygnus region hosts a giant molecular-cloud complex that actively forms massive stars. Interactions of cosmic rays with interstellar gas and radiation fields make it shine at γ-ray energies. Several γ-ray pulsars and other energetic sources are seen in this direction. Aims. In this paper we analyze the γ-ray emission measured by the Fermi Large Area Telescope (LAT) in the energy range from 100 MeV to 100 GeV in order to probe the gas and cosmic-ray content on the scale of the whole Cygnus complex. The γ-ray emission on the scale of the central massive stellar clusters and from individual sources is addressed elsewhere. Methods. The signal from bright pulsars is greatly reduced by selecting photons in their off-pulse phase intervals. We compare the diffuse γ-ray emission with interstellar gas maps derived from radio/mm-wave lines and visual extinction data. A general model of the region, including other pulsars and γ-ray sources, is sought. Results. The integral H i emissivity above 100 MeV averaged over the whole Cygnus complex amounts to [2.06 ± 0.11 (stat.) -0.84 +0.15(syst.)] × 10 -26 photons s -1 sr -1 H-atom -1, where the systematic error is dominated by the uncertainty on the H i opacity to calculate its column densities. The integral emissivity and its spectral energy distribution are both consistent within the systematics with LAT measurements in the interstellar space near the solar system. The average X CO = N(H 2)/W CO ratio is found to be [1.68 ± 0.05 (stat.) -0.10 +0.87(HI opacity)] × 10 20 molecules cm -2 (K km s -1) -1, consistent with other LAT measurements in the Local Arm. We detect significant γ-ray emission from dark neutral gas for a mass corresponding to ~40{\%} of what is traced by CO. The total interstellar mass in the Cygnus complex inferred from its γ-ray emission amounts to 8 -1 +5 × 10 6 M ⊙ at a distance of 1.4 kpc. Conclusions. Despite the conspicuous star formation activity and high masses of the interstellar clouds, the cosmic-ray population in the Cygnus complex averaged over a few hundred parsecs is similar to that of the local interstellar space.",
    keywords = "Cosmic rays, Gamma rays: ISM, ISM: abundances, ISM: clouds",
    author = "M. Ackermann and M. Ajello and A. Allafort and L. Baldini and J. Ballet and G. Barbiellini and D. Bastieri and A. Belfiore and R. Bellazzini and B. Berenji and Blandford, {R. D.} and Bloom, {E. D.} and E. Bonamente and Borgland, {A. W.} and E. Bottacini and J. Bregeon and M. Brigida and P. Bruel and R. Buehler and S. Buson and Caliandro, {G. A.} and Cameron, {R. A.} and Caraveo, {P. A.} and Casandjian, {J. M.} and C. Cecchi and A. Chekhtman and S. Ciprini and R. Claus and J. Cohen-Tanugi and {De Angelis}, A. and {De Palma}, F. and Dermer, {C. D.} and {Do Couto E Silva}, E. and Drell, {P. S.} and D. Dumora and C. Favuzzi and Fegan, {S. J.} and Focke, {W. B.} and P. Fortin and Y. Fukazawa and P. Fusco and F. Gargano and S. Germani and N. Giglietto and F. Giordano and M. Giroletti and T. Glanzman and G. Godfrey and Grenier, {I. A.} and L. Guillemot and S. Guiriec and D. Hadasch and Y. Hanabata and Harding, {A. K.} and M. Hayashida and K. Hayashi and E. Hays and G. J{\'o}hannesson and Johnson, {A. S.} and T. Kamae and H. Katagiri and Jun Kataoka and M. Kerr and J. Kn{\"o}dlseder and M. Kuss and J. Lande and L. Latronico and Lee, {S. H.} and F. Longo and F. Loparco and B. Lott and Lovellette, {M. N.} and P. Lubrano and P. Martin and Mazziotta, {M. N.} and McEnery, {J. E.} and J. Mehault and Michelson, {P. F.} and W. Mitthumsiri and T. Mizuno and C. Monte and Monzani, {M. E.} and A. Morselli and Moskalenko, {I. V.} and S. Murgia and M. Naumann-Godo and Nolan, {P. L.} and Norris, {J. P.} and E. Nuss and T. Ohsugi and A. Okumura and N. Omodei and E. Orlando and Ormes, {J. F.} and M. Ozaki and D. Paneque and D. Parent and M. Pesce-Rollins and M. Pierbattista and F. Piron and Porter, {T. A.} and S. Rain{\`o} and R. Rando and M. Razzano and O. Reimer and T. Reposeur and S. Ritz and {Saz Parkinson}, {P. M.} and C. Sgr{\`o} and Siskind, {E. J.} and Smith, {P. D.} and P. Spinelli and Strong, {A. W.} and H. Takahashi and T. Tanaka and Thayer, {J. G.} and Thayer, {J. B.} and Thompson, {D. J.} and L. Tibaldo and Torres, {D. F.} and G. Tosti and A. Tramacere and E. Troja and Y. Uchiyama and J. Vandenbroucke and V. Vasileiou and G. Vianello and V. Vitale and Waite, {A. P.} and P. Wang and Winer, {B. L.} and Wood, {K. S.} and Z. Yang and S. Zimmer and S. Bontemps",
    year = "2012",
    doi = "10.1051/0004-6361/201117539",
    language = "English",
    volume = "538",
    journal = "Astronomy and Astrophysics",
    issn = "0004-6361",
    publisher = "EDP Sciences",

    }

    TY - JOUR

    T1 - The cosmic-ray and gas content of the Cygnus region as measured in γ-rays by the Fermi Large Area Telescope

    AU - Ackermann, M.

    AU - Ajello, M.

    AU - Allafort, A.

    AU - Baldini, L.

    AU - Ballet, J.

    AU - Barbiellini, G.

    AU - Bastieri, D.

    AU - Belfiore, A.

    AU - Bellazzini, R.

    AU - Berenji, B.

    AU - Blandford, R. D.

    AU - Bloom, E. D.

    AU - Bonamente, E.

    AU - Borgland, A. W.

    AU - Bottacini, E.

    AU - Bregeon, J.

    AU - Brigida, M.

    AU - Bruel, P.

    AU - Buehler, R.

    AU - Buson, S.

    AU - Caliandro, G. A.

    AU - Cameron, R. A.

    AU - Caraveo, P. A.

    AU - Casandjian, J. M.

    AU - Cecchi, C.

    AU - Chekhtman, A.

    AU - Ciprini, S.

    AU - Claus, R.

    AU - Cohen-Tanugi, J.

    AU - De Angelis, A.

    AU - De Palma, F.

    AU - Dermer, C. D.

    AU - Do Couto E Silva, E.

    AU - Drell, P. S.

    AU - Dumora, D.

    AU - Favuzzi, C.

    AU - Fegan, S. J.

    AU - Focke, W. B.

    AU - Fortin, P.

    AU - Fukazawa, Y.

    AU - Fusco, P.

    AU - Gargano, F.

    AU - Germani, S.

    AU - Giglietto, N.

    AU - Giordano, F.

    AU - Giroletti, M.

    AU - Glanzman, T.

    AU - Godfrey, G.

    AU - Grenier, I. A.

    AU - Guillemot, L.

    AU - Guiriec, S.

    AU - Hadasch, D.

    AU - Hanabata, Y.

    AU - Harding, A. K.

    AU - Hayashida, M.

    AU - Hayashi, K.

    AU - Hays, E.

    AU - Jóhannesson, G.

    AU - Johnson, A. S.

    AU - Kamae, T.

    AU - Katagiri, H.

    AU - Kataoka, Jun

    AU - Kerr, M.

    AU - Knödlseder, J.

    AU - Kuss, M.

    AU - Lande, J.

    AU - Latronico, L.

    AU - Lee, S. H.

    AU - Longo, F.

    AU - Loparco, F.

    AU - Lott, B.

    AU - Lovellette, M. N.

    AU - Lubrano, P.

    AU - Martin, P.

    AU - Mazziotta, M. N.

    AU - McEnery, J. E.

    AU - Mehault, J.

    AU - Michelson, P. F.

    AU - Mitthumsiri, W.

    AU - Mizuno, T.

    AU - Monte, C.

    AU - Monzani, M. E.

    AU - Morselli, A.

    AU - Moskalenko, I. V.

    AU - Murgia, S.

    AU - Naumann-Godo, M.

    AU - Nolan, P. L.

    AU - Norris, J. P.

    AU - Nuss, E.

    AU - Ohsugi, T.

    AU - Okumura, A.

    AU - Omodei, N.

    AU - Orlando, E.

    AU - Ormes, J. F.

    AU - Ozaki, M.

    AU - Paneque, D.

    AU - Parent, D.

    AU - Pesce-Rollins, M.

    AU - Pierbattista, M.

    AU - Piron, F.

    AU - Porter, T. A.

    AU - Rainò, S.

    AU - Rando, R.

    AU - Razzano, M.

    AU - Reimer, O.

    AU - Reposeur, T.

    AU - Ritz, S.

    AU - Saz Parkinson, P. M.

    AU - Sgrò, C.

    AU - Siskind, E. J.

    AU - Smith, P. D.

    AU - Spinelli, P.

    AU - Strong, A. W.

    AU - Takahashi, H.

    AU - Tanaka, T.

    AU - Thayer, J. G.

    AU - Thayer, J. B.

    AU - Thompson, D. J.

    AU - Tibaldo, L.

    AU - Torres, D. F.

    AU - Tosti, G.

    AU - Tramacere, A.

    AU - Troja, E.

    AU - Uchiyama, Y.

    AU - Vandenbroucke, J.

    AU - Vasileiou, V.

    AU - Vianello, G.

    AU - Vitale, V.

    AU - Waite, A. P.

    AU - Wang, P.

    AU - Winer, B. L.

    AU - Wood, K. S.

    AU - Yang, Z.

    AU - Zimmer, S.

    AU - Bontemps, S.

    PY - 2012

    Y1 - 2012

    N2 - Context. The Cygnus region hosts a giant molecular-cloud complex that actively forms massive stars. Interactions of cosmic rays with interstellar gas and radiation fields make it shine at γ-ray energies. Several γ-ray pulsars and other energetic sources are seen in this direction. Aims. In this paper we analyze the γ-ray emission measured by the Fermi Large Area Telescope (LAT) in the energy range from 100 MeV to 100 GeV in order to probe the gas and cosmic-ray content on the scale of the whole Cygnus complex. The γ-ray emission on the scale of the central massive stellar clusters and from individual sources is addressed elsewhere. Methods. The signal from bright pulsars is greatly reduced by selecting photons in their off-pulse phase intervals. We compare the diffuse γ-ray emission with interstellar gas maps derived from radio/mm-wave lines and visual extinction data. A general model of the region, including other pulsars and γ-ray sources, is sought. Results. The integral H i emissivity above 100 MeV averaged over the whole Cygnus complex amounts to [2.06 ± 0.11 (stat.) -0.84 +0.15(syst.)] × 10 -26 photons s -1 sr -1 H-atom -1, where the systematic error is dominated by the uncertainty on the H i opacity to calculate its column densities. The integral emissivity and its spectral energy distribution are both consistent within the systematics with LAT measurements in the interstellar space near the solar system. The average X CO = N(H 2)/W CO ratio is found to be [1.68 ± 0.05 (stat.) -0.10 +0.87(HI opacity)] × 10 20 molecules cm -2 (K km s -1) -1, consistent with other LAT measurements in the Local Arm. We detect significant γ-ray emission from dark neutral gas for a mass corresponding to ~40% of what is traced by CO. The total interstellar mass in the Cygnus complex inferred from its γ-ray emission amounts to 8 -1 +5 × 10 6 M ⊙ at a distance of 1.4 kpc. Conclusions. Despite the conspicuous star formation activity and high masses of the interstellar clouds, the cosmic-ray population in the Cygnus complex averaged over a few hundred parsecs is similar to that of the local interstellar space.

    AB - Context. The Cygnus region hosts a giant molecular-cloud complex that actively forms massive stars. Interactions of cosmic rays with interstellar gas and radiation fields make it shine at γ-ray energies. Several γ-ray pulsars and other energetic sources are seen in this direction. Aims. In this paper we analyze the γ-ray emission measured by the Fermi Large Area Telescope (LAT) in the energy range from 100 MeV to 100 GeV in order to probe the gas and cosmic-ray content on the scale of the whole Cygnus complex. The γ-ray emission on the scale of the central massive stellar clusters and from individual sources is addressed elsewhere. Methods. The signal from bright pulsars is greatly reduced by selecting photons in their off-pulse phase intervals. We compare the diffuse γ-ray emission with interstellar gas maps derived from radio/mm-wave lines and visual extinction data. A general model of the region, including other pulsars and γ-ray sources, is sought. Results. The integral H i emissivity above 100 MeV averaged over the whole Cygnus complex amounts to [2.06 ± 0.11 (stat.) -0.84 +0.15(syst.)] × 10 -26 photons s -1 sr -1 H-atom -1, where the systematic error is dominated by the uncertainty on the H i opacity to calculate its column densities. The integral emissivity and its spectral energy distribution are both consistent within the systematics with LAT measurements in the interstellar space near the solar system. The average X CO = N(H 2)/W CO ratio is found to be [1.68 ± 0.05 (stat.) -0.10 +0.87(HI opacity)] × 10 20 molecules cm -2 (K km s -1) -1, consistent with other LAT measurements in the Local Arm. We detect significant γ-ray emission from dark neutral gas for a mass corresponding to ~40% of what is traced by CO. The total interstellar mass in the Cygnus complex inferred from its γ-ray emission amounts to 8 -1 +5 × 10 6 M ⊙ at a distance of 1.4 kpc. Conclusions. Despite the conspicuous star formation activity and high masses of the interstellar clouds, the cosmic-ray population in the Cygnus complex averaged over a few hundred parsecs is similar to that of the local interstellar space.

    KW - Cosmic rays

    KW - Gamma rays: ISM

    KW - ISM: abundances

    KW - ISM: clouds

    UR - http://www.scopus.com/inward/record.url?scp=84863012100&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=84863012100&partnerID=8YFLogxK

    U2 - 10.1051/0004-6361/201117539

    DO - 10.1051/0004-6361/201117539

    M3 - Article

    AN - SCOPUS:84863012100

    VL - 538

    JO - Astronomy and Astrophysics

    JF - Astronomy and Astrophysics

    SN - 0004-6361

    M1 - A71

    ER -