Gamma-ray observations of the orion molecular clouds with the fermi large area telescope

M. Ackermann; M. Ajello; A. Allafort; E. Antolini; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; K. Bechtol; R. Bellazzini; B. Berenji; R. D. Blandford; E. D. Bloom; E. Bonamente; A. W. Borgland; E. Bottacini; T. J. Brandt; J. Bregeon; M. Brigida; P. Bruel; R. Buehler; S. Buson; G. A. Caliandro; R. A. Cameron; P. A. Caraveo; C. Cecchi; A. Chekhtman; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; F. D'Ammando; A. De Angelis; F. De Palma; C. D. Dermer; E. Do Couto E Silva; P. S. Drell; A. Drlica-Wagner; T. Enoto; L. Falletti; C. Favuzzi; S. J. Fegan; E. C. Ferrara; W. B. Focke; Y. Fukazawa; Y. Fukui; P. Fusco; F. Gargano; D. Gasparrini; S. Germani; N. Giglietto; F. Giordano; M. Giroletti; T. Glanzman; G. Godfrey; S. Guiriec; D. Hadasch; Y. Hanabata; A. K. Harding; M. Hayashida; K. Hayashi; D. Horan; X. Hou; R. E. Hughes; M. S. Jackson; G. Jóhannesson; A. S. Johnson; T. Kamae; H. Katagiri; J. Kataoka; M. Kerr; J. Knödlseder; M. Kuss; J. Lande; S. Larsson; S. H. Lee; F. Longo; F. Loparco; M. N. Lovellette; P. Lubrano; K. Makishima; M. N. Mazziotta; J. Mehault; W. Mitthumsiri; A. A. Moiseev; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; T. Nakamori; M. Naumann-Godo; S. Nishino; J. P. Norris; E. Nuss; M. Ohno; T. Ohsugi; A. Okumura; M. Orienti; E. Orlando; J. F. Ormes; M. Ozaki; D. Paneque; J. H. Panetta; D. Parent; V. Pelassa; M. Pesce-Rollins; M. Pierbattista; F. Piron; G. Pivato; T. A. Porter; S. Rainò; M. Razzano; A. Reimer; O. Reimer; M. Roth; H. F.W. Sadrozinski; C. Sgrò; E. J. Siskind; G. Spandre; P. Spinelli; A. W. Strong; H. Takahashi; T. Takahashi; T. Tanaka; J. G. Thayer; J. B. Thayer; O. Tibolla; M. Tinivella; D. F. Torres; A. Tramacere; E. Troja; Y. Uchiyama; T. L. Usher; J. Vandenbroucke; V. Vasileiou; G. Vianello; V. Vitale; A. P. Waite; P. Wang; B. L. Winer; K. S. Wood; Z. Yang; S. Zimmer

doi:10.1088/0004-637X/756/1/4

Gamma-ray observations of the orion molecular clouds with the fermi large area telescope

M. Ackermann^*, M. Ajello, A. Allafort, E. Antolini, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, R. D. Blandford, E. D. Bloom, E. Bonamente, A. W. Borgland, E. Bottacini, T. J. Brandt, J. Bregeon, M. Brigida, P. BruelR. Buehler, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, C. Cecchi, A. Chekhtman, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, J. Conrad, F. D'Ammando, A. De Angelis, F. De Palma, C. D. Dermer, E. Do Couto E Silva, P. S. Drell, A. Drlica-Wagner, T. Enoto, L. Falletti, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, Y. Fukazawa, Y. Fukui, P. Fusco, F. Gargano, D. Gasparrini, S. Germani, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, S. Guiriec, D. Hadasch, Y. Hanabata, A. K. Harding, M. Hayashida, K. Hayashi, D. Horan, X. Hou, R. E. Hughes, M. S. Jackson, G. Jóhannesson, A. S. Johnson, T. Kamae, H. Katagiri, J. Kataoka, M. Kerr, J. Knödlseder, M. Kuss, J. Lande, S. Larsson, S. H. Lee, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, K. Makishima, M. N. Mazziotta, J. Mehault, W. Mitthumsiri, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, T. Nakamori, M. Naumann-Godo, S. Nishino, J. P. Norris, E. Nuss, M. Ohno, T. Ohsugi, A. Okumura, M. Orienti, E. Orlando, J. F. Ormes, M. Ozaki, D. Paneque, J. H. Panetta, D. Parent, V. Pelassa, M. Pesce-Rollins, M. Pierbattista, F. Piron, G. Pivato, T. A. Porter, S. Rainò, M. Razzano, A. Reimer, O. Reimer, M. Roth, H. F.W. Sadrozinski, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, A. W. Strong, H. Takahashi, T. Takahashi, T. Tanaka, J. G. Thayer, J. B. Thayer, O. Tibolla, M. Tinivella, D. F. Torres, A. Tramacere, E. Troja, Y. Uchiyama, T. L. Usher, J. Vandenbroucke, V. Vasileiou, G. Vianello, V. Vitale, A. P. Waite, P. Wang, B. L. Winer, K. S. Wood, Z. Yang, S. Zimmer

^*Corresponding author for this work

School of Advanced Science and Engineering

Research output: Contribution to journal › Article › peer-review

36 Citations (Scopus)

Abstract

We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between 100MeV and 100GeV is predicted to trace the gas mass distribution in the clouds through nuclear interactions between the Galactic cosmic rays (CRs) and interstellar gas. The gamma-ray production cross-section for the nuclear interaction is known to 10% precision which makes the LAT a powerful tool to measure the gas mass column density distribution of molecular clouds for a known CR intensity. We present here such distributions for Orion A and B, and correlate them with those of the velocity-integrated CO intensity (W _CO) at a 1° × 1°pixel level. The correlation is found to be linear over a W _CO range of ∼10-fold when divided in three regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The W _CO-to-mass conversion factor, X _CO, is found to be ∼2.3 × 10²⁰ cm^-2(K km s^-1)^-1 for the high-longitude part of Orion A (l > ∼212°), 1.7times higher than ∼1.3 × 10 ²⁰ found for the rest of Orion A and B. We interpret the apparent high X _CO in the high-longitude region of Orion A in the light of recent works proposing a nonlinear relation between H₂ and CO densities in the diffuse molecular gas. W _CO decreases faster than the H₂ column density in the region making the gas "darker" to W _CO.

Original language	English
Article number	4
Journal	Astrophysical Journal
Volume	756
Issue number	1
DOIs	https://doi.org/10.1088/0004-637X/756/1/4
Publication status	Published - 2012

Keywords

ISM: clouds
ISM: general
ISM: individual objects (Orion A and Orion B)
gamma rays: ISM

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1088/0004-637X/756/1/4

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Ackermann, M., Ajello, M., Allafort, A., Antolini, E., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bechtol, K., Bellazzini, R., Berenji, B., Blandford, R. D., Bloom, E. D., Bonamente, E., Borgland, A. W., Bottacini, E., Brandt, T. J., Bregeon, J., Brigida, M., ... Zimmer, S. (2012). Gamma-ray observations of the orion molecular clouds with the fermi large area telescope. Astrophysical Journal, 756(1), Article 4. https://doi.org/10.1088/0004-637X/756/1/4

Ackermann, M, Ajello, M, Allafort, A, Antolini, E, Baldini, L, Ballet, J, Barbiellini, G, Bastieri, D, Bechtol, K, Bellazzini, R, Berenji, B, Blandford, RD, Bloom, ED, Bonamente, E, Borgland, AW, Bottacini, E, Brandt, TJ, Bregeon, J, Brigida, M, Bruel, P, Buehler, R, Buson, S, Caliandro, GA, Cameron, RA, Caraveo, PA, Cecchi, C, Chekhtman, A, Chiang, J, Ciprini, S, Claus, R, Cohen-Tanugi, J, Conrad, J, D'Ammando, F, De Angelis, A, De Palma, F, Dermer, CD, Do Couto E Silva, E, Drell, PS, Drlica-Wagner, A, Enoto, T, Falletti, L, Favuzzi, C, Fegan, SJ, Ferrara, EC, Focke, WB, Fukazawa, Y, Fukui, Y, Fusco, P, Gargano, F, Gasparrini, D, Germani, S, Giglietto, N, Giordano, F, Giroletti, M, Glanzman, T, Godfrey, G, Guiriec, S, Hadasch, D, Hanabata, Y, Harding, AK, Hayashida, M, Hayashi, K, Horan, D, Hou, X, Hughes, RE, Jackson, MS, Jóhannesson, G, Johnson, AS, Kamae, T, Katagiri, H, Kataoka, J, Kerr, M, Knödlseder, J, Kuss, M, Lande, J, Larsson, S, Lee, SH, Longo, F, Loparco, F, Lovellette, MN, Lubrano, P, Makishima, K, Mazziotta, MN, Mehault, J, Mitthumsiri, W, Moiseev, AA, Monte, C, Monzani, ME, Morselli, A, Moskalenko, IV, Murgia, S, Nakamori, T, Naumann-Godo, M, Nishino, S, Norris, JP, Nuss, E, Ohno, M, Ohsugi, T, Okumura, A, Orienti, M, Orlando, E, Ormes, JF, Ozaki, M, Paneque, D, Panetta, JH, Parent, D, Pelassa, V, Pesce-Rollins, M, Pierbattista, M, Piron, F, Pivato, G, Porter, TA, Rainò, S, Razzano, M, Reimer, A, Reimer, O, Roth, M, Sadrozinski, HFW, Sgrò, C, Siskind, EJ, Spandre, G, Spinelli, P, Strong, AW, Takahashi, H, Takahashi, T, Tanaka, T, Thayer, JG, Thayer, JB, Tibolla, O, Tinivella, M, Torres, DF, Tramacere, A, Troja, E, Uchiyama, Y, Usher, TL, Vandenbroucke, J, Vasileiou, V, Vianello, G, Vitale, V, Waite, AP, Wang, P, Winer, BL, Wood, KS, Yang, Z & Zimmer, S 2012, 'Gamma-ray observations of the orion molecular clouds with the fermi large area telescope', Astrophysical Journal, vol. 756, no. 1, 4. https://doi.org/10.1088/0004-637X/756/1/4

@article{2f791fe03d194ddcb2154a688f82d81b,

title = "Gamma-ray observations of the orion molecular clouds with the fermi large area telescope",

abstract = "We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between 100MeV and 100GeV is predicted to trace the gas mass distribution in the clouds through nuclear interactions between the Galactic cosmic rays (CRs) and interstellar gas. The gamma-ray production cross-section for the nuclear interaction is known to 10% precision which makes the LAT a powerful tool to measure the gas mass column density distribution of molecular clouds for a known CR intensity. We present here such distributions for Orion A and B, and correlate them with those of the velocity-integrated CO intensity (W CO) at a 1° × 1°pixel level. The correlation is found to be linear over a W CO range of ∼10-fold when divided in three regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The W CO-to-mass conversion factor, X CO, is found to be ∼2.3 × 1020 cm-2(K km s-1)-1 for the high-longitude part of Orion A (l > ∼212°), 1.7times higher than ∼1.3 × 10 20 found for the rest of Orion A and B. We interpret the apparent high X CO in the high-longitude region of Orion A in the light of recent works proposing a nonlinear relation between H2 and CO densities in the diffuse molecular gas. W CO decreases faster than the H2 column density in the region making the gas {"}darker{"} to W CO.",

keywords = "ISM: clouds, ISM: general, ISM: individual objects (Orion A and Orion B), gamma rays: ISM",

author = "M. Ackermann and M. Ajello and A. Allafort and E. Antolini and L. Baldini and J. Ballet and G. Barbiellini and D. Bastieri and K. Bechtol 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 Brandt, {T. J.} 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 C. Cecchi and A. Chekhtman and J. Chiang and S. Ciprini and R. Claus and J. Cohen-Tanugi and J. Conrad and F. D'Ammando and {De Angelis}, A. and {De Palma}, F. and Dermer, {C. D.} and {Do Couto E Silva}, E. and Drell, {P. S.} and A. Drlica-Wagner and T. Enoto and L. Falletti and C. Favuzzi and Fegan, {S. J.} and Ferrara, {E. C.} and Focke, {W. B.} and Y. Fukazawa and Y. Fukui and P. Fusco and F. Gargano and D. Gasparrini and S. Germani and N. Giglietto and F. Giordano and M. Giroletti and T. Glanzman and G. Godfrey and S. Guiriec and D. Hadasch and Y. Hanabata and Harding, {A. K.} and M. Hayashida and K. Hayashi and D. Horan and X. Hou and Hughes, {R. E.} and Jackson, {M. S.} and G. J{\'o}hannesson and Johnson, {A. S.} and T. Kamae and H. Katagiri and J. Kataoka and M. Kerr and J. Kn{\"o}dlseder and M. Kuss and J. Lande and S. Larsson and Lee, {S. H.} and F. Longo and F. Loparco and Lovellette, {M. N.} and P. Lubrano and K. Makishima and Mazziotta, {M. N.} and J. Mehault and W. Mitthumsiri and Moiseev, {A. A.} and C. Monte and Monzani, {M. E.} and A. Morselli and Moskalenko, {I. V.} and S. Murgia and T. Nakamori and M. Naumann-Godo and S. Nishino and Norris, {J. P.} and E. Nuss and M. Ohno and T. Ohsugi and A. Okumura and M. Orienti and E. Orlando and Ormes, {J. F.} and M. Ozaki and D. Paneque and Panetta, {J. H.} and D. Parent and V. Pelassa and M. Pesce-Rollins and M. Pierbattista and F. Piron and G. Pivato and Porter, {T. A.} and S. Rain{\`o} and M. Razzano and A. Reimer and O. Reimer and M. Roth and Sadrozinski, {H. F.W.} and C. Sgr{\`o} and Siskind, {E. J.} and G. Spandre and P. Spinelli and Strong, {A. W.} and H. Takahashi and T. Takahashi and T. Tanaka and Thayer, {J. G.} and Thayer, {J. B.} and O. Tibolla and M. Tinivella and Torres, {D. F.} and A. Tramacere and E. Troja and Y. Uchiyama and Usher, {T. L.} 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",

year = "2012",

doi = "10.1088/0004-637X/756/1/4",

language = "English",

volume = "756",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "IOP Publishing Ltd.",

number = "1",

}

TY - JOUR

T1 - Gamma-ray observations of the orion molecular clouds with the fermi large area telescope

AU - Ackermann, M.

AU - Ajello, M.

AU - Allafort, A.

AU - Antolini, E.

AU - Baldini, L.

AU - Ballet, J.

AU - Barbiellini, G.

AU - Bastieri, D.

AU - Bechtol, K.

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 - Brandt, T. J.

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 - Cecchi, C.

AU - Chekhtman, A.

AU - Chiang, J.

AU - Ciprini, S.

AU - Claus, R.

AU - Cohen-Tanugi, J.

AU - Conrad, J.

AU - D'Ammando, F.

AU - De Angelis, A.

AU - De Palma, F.

AU - Dermer, C. D.

AU - Do Couto E Silva, E.

AU - Drell, P. S.

AU - Drlica-Wagner, A.

AU - Enoto, T.

AU - Falletti, L.

AU - Favuzzi, C.

AU - Fegan, S. J.

AU - Ferrara, E. C.

AU - Focke, W. B.

AU - Fukazawa, Y.

AU - Fukui, Y.

AU - Fusco, P.

AU - Gargano, F.

AU - Gasparrini, D.

AU - Germani, S.

AU - Giglietto, N.

AU - Giordano, F.

AU - Giroletti, M.

AU - Glanzman, T.

AU - Godfrey, G.

AU - Guiriec, S.

AU - Hadasch, D.

AU - Hanabata, Y.

AU - Harding, A. K.

AU - Hayashida, M.

AU - Hayashi, K.

AU - Horan, D.

AU - Hou, X.

AU - Hughes, R. E.

AU - Jackson, M. S.

AU - Jóhannesson, G.

AU - Johnson, A. S.

AU - Kamae, T.

AU - Katagiri, H.

AU - Kataoka, J.

AU - Kerr, M.

AU - Knödlseder, J.

AU - Kuss, M.

AU - Lande, J.

AU - Larsson, S.

AU - Lee, S. H.

AU - Longo, F.

AU - Loparco, F.

AU - Lovellette, M. N.

AU - Lubrano, P.

AU - Makishima, K.

AU - Mazziotta, M. N.

AU - Mehault, J.

AU - Mitthumsiri, W.

AU - Moiseev, A. A.

AU - Monte, C.

AU - Monzani, M. E.

AU - Morselli, A.

AU - Moskalenko, I. V.

AU - Murgia, S.

AU - Nakamori, T.

AU - Naumann-Godo, M.

AU - Nishino, S.

AU - Norris, J. P.

AU - Nuss, E.

AU - Ohno, M.

AU - Ohsugi, T.

AU - Okumura, A.

AU - Orienti, M.

AU - Orlando, E.

AU - Ormes, J. F.

AU - Ozaki, M.

AU - Paneque, D.

AU - Panetta, J. H.

AU - Parent, D.

AU - Pelassa, V.

AU - Pesce-Rollins, M.

AU - Pierbattista, M.

AU - Piron, F.

AU - Pivato, G.

AU - Porter, T. A.

AU - Rainò, S.

AU - Razzano, M.

AU - Reimer, A.

AU - Reimer, O.

AU - Roth, M.

AU - Sadrozinski, H. F.W.

AU - Sgrò, C.

AU - Siskind, E. J.

AU - Spandre, G.

AU - Spinelli, P.

AU - Strong, A. W.

AU - Takahashi, H.

AU - Takahashi, T.

AU - Tanaka, T.

AU - Thayer, J. G.

AU - Thayer, J. B.

AU - Tibolla, O.

AU - Tinivella, M.

AU - Torres, D. F.

AU - Tramacere, A.

AU - Troja, E.

AU - Uchiyama, Y.

AU - Usher, T. L.

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.

PY - 2012

Y1 - 2012

N2 - We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between 100MeV and 100GeV is predicted to trace the gas mass distribution in the clouds through nuclear interactions between the Galactic cosmic rays (CRs) and interstellar gas. The gamma-ray production cross-section for the nuclear interaction is known to 10% precision which makes the LAT a powerful tool to measure the gas mass column density distribution of molecular clouds for a known CR intensity. We present here such distributions for Orion A and B, and correlate them with those of the velocity-integrated CO intensity (W CO) at a 1° × 1°pixel level. The correlation is found to be linear over a W CO range of ∼10-fold when divided in three regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The W CO-to-mass conversion factor, X CO, is found to be ∼2.3 × 1020 cm-2(K km s-1)-1 for the high-longitude part of Orion A (l > ∼212°), 1.7times higher than ∼1.3 × 10 20 found for the rest of Orion A and B. We interpret the apparent high X CO in the high-longitude region of Orion A in the light of recent works proposing a nonlinear relation between H2 and CO densities in the diffuse molecular gas. W CO decreases faster than the H2 column density in the region making the gas "darker" to W CO.

AB - We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between 100MeV and 100GeV is predicted to trace the gas mass distribution in the clouds through nuclear interactions between the Galactic cosmic rays (CRs) and interstellar gas. The gamma-ray production cross-section for the nuclear interaction is known to 10% precision which makes the LAT a powerful tool to measure the gas mass column density distribution of molecular clouds for a known CR intensity. We present here such distributions for Orion A and B, and correlate them with those of the velocity-integrated CO intensity (W CO) at a 1° × 1°pixel level. The correlation is found to be linear over a W CO range of ∼10-fold when divided in three regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The W CO-to-mass conversion factor, X CO, is found to be ∼2.3 × 1020 cm-2(K km s-1)-1 for the high-longitude part of Orion A (l > ∼212°), 1.7times higher than ∼1.3 × 10 20 found for the rest of Orion A and B. We interpret the apparent high X CO in the high-longitude region of Orion A in the light of recent works proposing a nonlinear relation between H2 and CO densities in the diffuse molecular gas. W CO decreases faster than the H2 column density in the region making the gas "darker" to W CO.

KW - ISM: clouds

KW - ISM: general

KW - ISM: individual objects (Orion A and Orion B)

KW - gamma rays: ISM

UR - http://www.scopus.com/inward/record.url?scp=84865184972&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84865184972&partnerID=8YFLogxK

U2 - 10.1088/0004-637X/756/1/4

DO - 10.1088/0004-637X/756/1/4

M3 - Article

AN - SCOPUS:84865184972

SN - 0004-637X

VL - 756

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1

M1 - 4

ER -

Gamma-ray observations of the orion molecular clouds with the fermi large area telescope

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