NuSTAR observations of the powerful radio-galaxy Cygnus A
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- Univ. of Maryland, College Park, MD (United States); Joint Space-Science Institute (JSI), College Park, MD (United States)
- Institute of Astronomy, Cambridge (United Kingdom)
- California Inst. of Technology (CalTech), Pasadena, CA (United States)
- NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Georgia Inst. of Technology, Atlanta, GA (United States)
- Univ. of California, Berkeley, CA (United States)
- Technical Univ. of Denmark, Lyngby (Denmark)
- Univ. of California, Berkeley, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Columbia Univ., New York, NY (United States)
- Univ. of Michigan, Ann Arbor, MI (United States)
- Univ. of Maryland, College Park, MD (United States)
Here, we present NuSTAR observations of the powerful radio galaxy Cygnus A, focusing on the central absorbed active galactic nucleus (AGN). Cygnus A is embedded in a cool-core galaxy cluster, and hence we also examine archival XMM-Newton data to facilitate the decomposition of the spectrum into the AGN and intracluster medium components. NuSTAR gives a source-dominated spectrum of the AGN out to $$\gt 70$$ keV. In gross terms, the NuSTAR spectrum of the AGN has the form of a power law ($${\rm{\Gamma }}\sim 1.6-1.7$$) absorbed by a neutral column density of $${N}_{{\rm{H}}}\sim 1.6\times {10}^{23}\;\;{\mathrm{cm}}^{-2}$$. However, we also detect curvature in the hard ($$\gt 10$$ keV) spectrum resulting from reflection by Compton-thick matter out of our line of sight to the X-ray source. Compton reflection, possibly from the outer accretion disk or obscuring torus, is required even permitting a high-energy cut off in the continuum source; the limit on the cut-off energy is $${E}_{\mathrm{cut}}\gt 111$$ keV(90% confidence). Interestingly, the absorbed power law plus reflection model leaves residuals suggesting the absorption/emission from a fast ($$15,000-26,000\;\;\mathrm{km}\;\;{{\rm{s}}}^{-1}\;$$), high column-density ($${N}_{W}\gt 3\times {10}^{23}\;\;{\mathrm{cm}}^{-2}$$), highly ionized ($$\xi \sim 2500\;\mathrm{erg}\;\mathrm{cm}\;{{\rm{s}}}^{-1}$$) wind. A second, even faster ionized wind component is also suggested by these data. We show that the ionized wind likely carries a significant mass and momentum flux, and may carry sufficient kinetic energy to exercise feedback on the host galaxy. If confirmed, the simultaneous presence of a strong wind and powerful jets in Cygnus A demonstrates that feedback from radio-jets and sub-relativistic winds are not mutually exclusive phases of AGN activity but can occur simultaneously.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); National Aeronautics and Space Administration (NASA)
- Grant/Contract Number:
- AC02-76SF00515
- OSTI ID:
- 1313945
- Report Number(s):
- SLAC-PUB-16797; arXiv:1506.07175
- Journal Information:
- The Astrophysical Journal (Online), Vol. 808, Issue 2; ISSN 1538-4357
- Publisher:
- Institute of Physics (IOP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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