| _version_ |
1826208226058698752
|
| author2 |
MIT Kavli Institute for Astrophysics and Space Research
|
| author_facet |
MIT Kavli Institute for Astrophysics and Space Research
|
| collection |
MIT
|
| description |
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. A preferred alignment of the γ-ray elongation with the radio lobes was demonstrated 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. 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. ©2014
|
| first_indexed |
2024-09-23T14:02:30Z
|
| format |
Article
|
| id |
mit-1721.1/124790
|
| institution |
Massachusetts Institute of Technology
|
| last_indexed |
2024-09-23T14:02:30Z
|
| publishDate |
2020
|
| publisher |
American Astronomical Society
|
| record_format |
dspace
|
| spelling |
mit-1721.1/1247902022-09-28T17:54:45Z Fermi Large Area Telescope detection of extended gamma-ray emission from the radio galaxy Fornax A MIT Kavli Institute for Astrophysics and Space Research 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. A preferred alignment of the γ-ray elongation with the radio lobes was demonstrated 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. 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. ©2014 2020-04-22T15:22:26Z 2020-04-22T15:22:26Z 2016-07 2018-04-24T14:54:26Z Article http://purl.org/eprint/type/JournalArticle 1538-4357 https://hdl.handle.net/1721.1/124790 Ackermann, M., et al., "Fermi Large Area Telescope detection of extended gamma-ray emission from the radio galaxy Fornax A." Astrophysical journal 826 (July 2016): no. 1 doi 10.3847/0004-637X/826/1/1 ©2016 Author(s) 10.3847/0004-637X/826/1/1 Astrophysical journal Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Astronomical Society IOP Publishing
|
| spellingShingle |
Fermi Large Area Telescope detection of extended gamma-ray emission from the radio galaxy Fornax A
|
| title |
Fermi Large Area Telescope detection of extended gamma-ray emission from the radio galaxy Fornax A
|
| title_full |
Fermi Large Area Telescope detection of extended gamma-ray emission from the radio galaxy Fornax A
|
| title_fullStr |
Fermi Large Area Telescope detection of extended gamma-ray emission from the radio galaxy Fornax A
|
| title_full_unstemmed |
Fermi Large Area Telescope detection of extended gamma-ray emission from the radio galaxy Fornax A
|
| title_short |
Fermi Large Area Telescope detection of extended gamma-ray emission from the radio galaxy Fornax A
|
| title_sort |
fermi large area telescope detection of extended gamma ray emission from the radio galaxy fornax a
|
| url |
https://hdl.handle.net/1721.1/124790
|