FERMI LARGE AREA TELESCOPE VIEW OF THE CORE OF THE RADIO GALAXY CENTAURUS A

By A. Abdo, M. Ackermann, M. Ajello, W. Atwood, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, B. Baughman, K. Bechtol and 188 more. 2010

146 citations recorded by the source corpus.

We present γ-ray observations with the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope of the nearby radio galaxy Centaurus A (Cen A). The previous EGRET detection is confirmed, and the localization is improved using data from the first 10 months of Fermi science operation. In previous work, we presented the detection of the lobes by the LAT; in this work, we concentrate on the γ-ray core of Cen A. Flux levels as seen by the LAT are not significantly different from that found by EGRET, nor is the extremely soft LAT spectrum (Γ = 2.67 ± 0.10stat ± 0.08sys where the photon flux is Φ ∝ E−Γ). The LAT core spectrum, extrapolated to higher energies, is marginally consistent with the non-simultaneous HESS spectrum of the source. The LAT observations are complemented by simultaneous observations from Suzaku, the Swift Burst Alert Telescope and X-ray Telescope, and radio observations with the Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry program, along with a variety of non-simultaneous archival data from a variety of instruments and wavelengths to produce a spectral energy distribution (SED). We fit this broadband data set with a single-zone synchrotron/synchrotron self-Compton model, which describes the radio through GeV emission well, but fails to account for the non-simultaneous higher energy TeV emission observed by HESS from 2004 to 2008. The fit requires a low Doppler factor, in contrast to BL Lac objects which generally require larger values to fit their broadband SEDs. This indicates that the γ-ray emission originates from a slower region than that from BL Lac objects, consistent with previous modeling results from Cen A. This slower region could be a slower moving layer around a fast spine, or a slower region farther out from the black hole in a decelerating flow. The fit parameters are also consistent with Cen A being able to accelerate ultra-high energy cosmic-rays, as hinted at by results from the Auger observatory.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/3a949443d62bf90279e33af49a6508d5dcd8223f

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In Astronomy and Astrophysics

1. A. Strong
2. E. Orlando
3. Bing Zhang
4. Troy A. Porter
5. Y. Inoue
6. Igor V. Moskalenko
7. Kohta Murase
8. A. Reimer

In Nuclear and High Energy Physics

1. A. Strong
2. E. Orlando
3. Troy A. Porter
4. Y. Inoue
5. I. Grenier
6. Kohta Murase
7. Igor V. Moskalenko
8. A. Reimer

Citations in the corpus

• The extragalactic background light and the gamma-ray opacity of the universe (2012, background): “…in the GeV regime (Abdo, A. A. et al., 2010), while the spectra of other blazars (Mrk 421, Abdo et al., 2011b), (Mrk 501, Abdo et al., 2011a) extend without any cutoff to 300 GeV (Abdo et al., 2010b), or multi-TeV energies (Krennrich et al., 2002), depending on the flaring state of the source.”
• FERMI LARGE AREA TELESCOPE OBSERVATIONS OF MISALIGNED ACTIVE GALACTIC NUCLEI (2010, methodology): “LAT sources are positionally associated at high probability with the seven FRI radio galaxies and the two SSRQs and are included in the 1LAC (Table 1 in Abdo et al. 2010a).”
• GeV OBSERVATIONS OF STAR-FORMING GALAXIES WITH THE FERMI LARGE AREA TELESCOPE (2012, methodology): “…by harder gamma-ray spectra relative to quiescent galaxies of the Local Group (Acero et al. 2009; Acciari et al. 2009; Abdo et al. 2010a; Ohm et al. 2011), and that global gammaray luminosities of galaxies likely scale quasi-linearly with SFRs (e.g. Abdo et al. 2010a,d; Lenain & Walter 2011).”
• First X-ray-based statistical tests for clumpy-torus models: eclipse events from 230 years of monitoring of Seyfert AGN (2014, methodology): “Using 0.66 as the spectral index (Abdo et al. 2010), the flux will be boosted by δ2+α ∼ 1.6, which translates into only a ∼ 26 per cent effect on our estimate of Rd. 2009b, 2011; Maiolino et al. 2010).”
• CONTRIBUTION OF GAMMA-RAY-LOUD RADIO GALAXIES’ CORE EMISSIONS TO THE COSMIC MeV AND GeV GAMMA-RAY BACKGROUND RADIATION (2011, methodology): “Their average photon index at 0.1–10 GeV is ∼2.4, which is the same as that of the GeV EGRB (Abdo et al. 2010e) and blazars (Abdo et al. 2010f).”
• BLAZARS AS ULTRA-HIGH-ENERGY COSMIC-RAY SOURCES: IMPLICATIONS FOR TeV GAMMA-RAY OBSERVATIONS (2011, methodology): “VHE BLAZARS AND UHECRS Of the wide variety of source classes that could potentially accelerate UHECRs, including, for example, GRBs (Waxman 1995; Vietri 1995; Murase et al. 2008a), fast rotating magnetars (Arons 2003), structure formation shocks in galaxy clusters (Norman et al. 1995; Kang et al. 19”