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Title: Fermi large area telescope detection of extended gamma-ray emission from the radio galaxy fornax A

Here, we report the Fermi Large Area Telescope detection of extended γ-ray emission from the lobes of the radio galaxy Fornax A using 6.1 years of Pass 8 data. After Centaurus A, this is now the second example of an extended γ-ray source attributed to a radio galaxy. Both an extended flat disk morphology and a morphology following the extended radio lobes were preferred over a point-source description, and the core contribution was constrained to be $$\lt 14$$% of the total γ-ray flux. We also demonstrated a preferred alignment of the γ-ray elongation with the radio lobes by rotating the radio lobes template. We found no significant evidence for variability on ~0.5 year timescales. Taken together, these results strongly suggest a lobe origin for the γ-rays. Furthermore, with the extended nature of the $$\gt 100\;{\rm{MeV}}$$ γ-ray emission established, we model the source broadband emission considering currently available total lobe radio and millimeter flux measurements, as well as X-ray detections attributed to inverse Compton (IC) emission off the cosmic microwave background (CMB). Unlike the Centaurus A case, we find that a leptonic model involving IC scattering of CMB and extragalactic background light (EBL) photons underpredicts the γ-ray fluxes by factors of about ~2–3, depending on the EBL model adopted. An additional γ-ray spectral component is thus required, and could be due to hadronic emission arising from proton–proton collisions of cosmic rays with thermal plasma within the radio lobes.
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Publication Date:
Grant/Contract Number:
AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 826; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE; National Aeronautics and Space Administration (NASA); Alternative Energies and Atomic Energy Commission (CEA)
Contributing Orgs:
Fermi LAT Collaboration
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; galaxies: active; galaxies: individual (Fornax A); galaxies: jets; gamma rays: galaxies; radiation mechanisms: non-thermal
OSTI Identifier:
1355705

Ackermann, M., Ajello, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Cheung, C. C., Chiaro, G., Ciprini, S., Cohen, J. M., Cohen-Tanugi, J., Costanza, F., Cutini, S., D’Ammando, F., Davis, D. S., Angelis, A. de, Palma, F. de, Desiante, R., Digel, S. W., Lalla, N. Di, Mauro, M. Di, Venere, L. Di, Favuzzi, C., Fegan, S. J., Ferrara, E. C., Focke, W. B., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Georganopoulos, M., Giglietto, N., Giordano, F., Giroletti, M., Godfrey, G., Green, D., Grenier, I. A., Guiriec, S., Hays, E., Hewitt, J. W., Hill, A. B., Jogler, T., Jóhannesson, G., Kensei, S., Kuss, M., Larsson, S., Latronico, L., Li, J., Li, L., Longo, F., Loparco, F., Lubrano, P., Magill, J. D., Maldera, S., Manfreda, A., Mayer, M., Mazziotta, M. N., McConville, W., McEnery, J. E., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Negro, M., Nuss, E., Ohno, M., Ohsugi, T., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Piron, F., Pivato, G., Porter, T. A., Rainò, S., Rando, R., Razzano, M., Reimer, A., Reimer, O., Schmid, J., Sgrò, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Stawarz, Ł., Takahashi, H., Thayer, J. B., Thompson, D. J., Torres, D. F., Tosti, G., Troja, E., Vianello, G., Wood, K. S., Wood, M., and Zimmer, S.. Fermi large area telescope detection of extended gamma-ray emission from the radio galaxy fornax A. United States: N. p., Web. doi:10.3847/0004-637X/826/1/1.
Ackermann, M., Ajello, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Cheung, C. C., Chiaro, G., Ciprini, S., Cohen, J. M., Cohen-Tanugi, J., Costanza, F., Cutini, S., D’Ammando, F., Davis, D. S., Angelis, A. de, Palma, F. de, Desiante, R., Digel, S. W., Lalla, N. Di, Mauro, M. Di, Venere, L. Di, Favuzzi, C., Fegan, S. J., Ferrara, E. C., Focke, W. B., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Georganopoulos, M., Giglietto, N., Giordano, F., Giroletti, M., Godfrey, G., Green, D., Grenier, I. A., Guiriec, S., Hays, E., Hewitt, J. W., Hill, A. B., Jogler, T., Jóhannesson, G., Kensei, S., Kuss, M., Larsson, S., Latronico, L., Li, J., Li, L., Longo, F., Loparco, F., Lubrano, P., Magill, J. D., Maldera, S., Manfreda, A., Mayer, M., Mazziotta, M. N., McConville, W., McEnery, J. E., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Negro, M., Nuss, E., Ohno, M., Ohsugi, T., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Piron, F., Pivato, G., Porter, T. A., Rainò, S., Rando, R., Razzano, M., Reimer, A., Reimer, O., Schmid, J., Sgrò, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Stawarz, Ł., Takahashi, H., Thayer, J. B., Thompson, D. J., Torres, D. F., Tosti, G., Troja, E., Vianello, G., Wood, K. S., Wood, M., & Zimmer, S.. Fermi large area telescope detection of extended gamma-ray emission from the radio galaxy fornax A. United States. doi:10.3847/0004-637X/826/1/1.
Ackermann, M., Ajello, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Cheung, C. C., Chiaro, G., Ciprini, S., Cohen, J. M., Cohen-Tanugi, J., Costanza, F., Cutini, S., D’Ammando, F., Davis, D. S., Angelis, A. de, Palma, F. de, Desiante, R., Digel, S. W., Lalla, N. Di, Mauro, M. Di, Venere, L. Di, Favuzzi, C., Fegan, S. J., Ferrara, E. C., Focke, W. B., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Georganopoulos, M., Giglietto, N., Giordano, F., Giroletti, M., Godfrey, G., Green, D., Grenier, I. A., Guiriec, S., Hays, E., Hewitt, J. W., Hill, A. B., Jogler, T., Jóhannesson, G., Kensei, S., Kuss, M., Larsson, S., Latronico, L., Li, J., Li, L., Longo, F., Loparco, F., Lubrano, P., Magill, J. D., Maldera, S., Manfreda, A., Mayer, M., Mazziotta, M. N., McConville, W., McEnery, J. E., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Negro, M., Nuss, E., Ohno, M., Ohsugi, T., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Piron, F., Pivato, G., Porter, T. A., Rainò, S., Rando, R., Razzano, M., Reimer, A., Reimer, O., Schmid, J., Sgrò, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Stawarz, Ł., Takahashi, H., Thayer, J. B., Thompson, D. J., Torres, D. F., Tosti, G., Troja, E., Vianello, G., Wood, K. S., Wood, M., and Zimmer, S.. 2016. "Fermi large area telescope detection of extended gamma-ray emission from the radio galaxy fornax A". United States. doi:10.3847/0004-637X/826/1/1. https://www.osti.gov/servlets/purl/1355705.
@article{osti_1355705,
title = {Fermi large area telescope detection of extended gamma-ray emission from the radio galaxy fornax A},
author = {Ackermann, M. and Ajello, M. and Baldini, L. and Ballet, J. and Barbiellini, G. and Bastieri, D. and Bellazzini, R. and Bissaldi, E. and Blandford, R. D. and Bloom, E. D. and Bonino, R. and Brandt, T. J. and Bregeon, J. and Bruel, P. and Buehler, R. and Buson, S. and Caliandro, G. A. and Cameron, R. A. and Caragiulo, M. and Caraveo, P. A. and Cavazzuti, E. and Cecchi, C. and Charles, E. and Chekhtman, A. and Cheung, C. C. and Chiaro, G. and Ciprini, S. and Cohen, J. M. and Cohen-Tanugi, J. and Costanza, F. and Cutini, S. and D’Ammando, F. and Davis, D. S. and Angelis, A. de and Palma, F. de and Desiante, R. and Digel, S. W. and Lalla, N. Di and Mauro, M. Di and Venere, L. Di and Favuzzi, C. and Fegan, S. J. and Ferrara, E. C. and Focke, W. B. and Fukazawa, Y. and Funk, S. and Fusco, P. and Gargano, F. and Gasparrini, D. and Georganopoulos, M. and Giglietto, N. and Giordano, F. and Giroletti, M. and Godfrey, G. and Green, D. and Grenier, I. A. and Guiriec, S. and Hays, E. and Hewitt, J. W. and Hill, A. B. and Jogler, T. and Jóhannesson, G. and Kensei, S. and Kuss, M. and Larsson, S. and Latronico, L. and Li, J. and Li, L. and Longo, F. and Loparco, F. and Lubrano, P. and Magill, J. D. and Maldera, S. and Manfreda, A. and Mayer, M. and Mazziotta, M. N. and McConville, W. and McEnery, J. E. and Michelson, P. F. and Mitthumsiri, W. and Mizuno, T. and Monzani, M. E. and Morselli, A. and Moskalenko, I. V. and Murgia, S. and Negro, M. and Nuss, E. and Ohno, M. and Ohsugi, T. and Orienti, M. and Orlando, E. and Ormes, J. F. and Paneque, D. and Perkins, J. S. and Pesce-Rollins, M. and Piron, F. and Pivato, G. and Porter, T. A. and Rainò, S. and Rando, R. and Razzano, M. and Reimer, A. and Reimer, O. and Schmid, J. and Sgrò, C. and Simone, D. and Siskind, E. J. and Spada, F. and Spandre, G. and Spinelli, P. and Stawarz, Ł. and Takahashi, H. and Thayer, J. B. and Thompson, D. J. and Torres, D. F. and Tosti, G. and Troja, E. and Vianello, G. and Wood, K. S. and Wood, M. and Zimmer, S.},
abstractNote = {Here, we report the Fermi Large Area Telescope detection of extended γ-ray emission from the lobes of the radio galaxy Fornax A using 6.1 years of Pass 8 data. After Centaurus A, this is now the second example of an extended γ-ray source attributed to a radio galaxy. Both an extended flat disk morphology and a morphology following the extended radio lobes were preferred over a point-source description, and the core contribution was constrained to be $\lt 14$% of the total γ-ray flux. We also demonstrated a preferred alignment of the γ-ray elongation with the radio lobes by rotating the radio lobes template. We found no significant evidence for variability on ~0.5 year timescales. Taken together, these results strongly suggest a lobe origin for the γ-rays. Furthermore, with the extended nature of the $\gt 100\;{\rm{MeV}}$ γ-ray emission established, we model the source broadband emission considering currently available total lobe radio and millimeter flux measurements, as well as X-ray detections attributed to inverse Compton (IC) emission off the cosmic microwave background (CMB). Unlike the Centaurus A case, we find that a leptonic model involving IC scattering of CMB and extragalactic background light (EBL) photons underpredicts the γ-ray fluxes by factors of about ~2–3, depending on the EBL model adopted. An additional γ-ray spectral component is thus required, and could be due to hadronic emission arising from proton–proton collisions of cosmic rays with thermal plasma within the radio lobes.},
doi = {10.3847/0004-637X/826/1/1},
journal = {The Astrophysical Journal (Online)},
number = 1,
volume = 826,
place = {United States},
year = {2016},
month = {7}
}