Constraining the Outburst Properties of the SMBH in Fornax A through
  X-ray, Infrared, and Radio Observations
  Combined Spitzer, Chandra, XMM-Newton, and VLA observations of the giant
radio galaxy NGC 1316 (Fornax A) show a radio jet and X-ray cavities from AGN
outbursts likely triggered by a merger with a late-type galaxy at least 0.4 Gyr
ago. We detect a weak nucleus with an SED typical of a low-luminosity AGN with
a bolometric luminosity of 2.4x10^42 erg/s. The Spitzer IRAC and MIPS images
show dust emission strongest in regions with little or no radio emission. The
large infrared luminosity relative to the galaxy's K-band luminosity implies an
external origin for the dust. The dust mass implies that the merger spiral
galaxy had a stellar mass of 1-6x10^10 M_sun and a gas mass of 2-4x10^9 M_sun.
Chandra images show a small ~15"(1.6 kpc) cavity coincident with the radio jet,
while the XMM-Newton image shows two large X-ray cavities lying 320"(34.8 kpc)
east and west of the nucleus, each approximately 230"(25 kpc) in radius. The
radio lobes lie at radii of 14.3'(93 kpc) and 15.6'(101 kcp), more distant from
the nucleus than the detected X-ray cavities. The relative morphology of the
large scale 1.4 GHz and X-ray emission suggests they were products of two
distinct outbursts, an earlier one creating the radio lobes and a later one
producing the X-ray cavities. Alternatively, if a single outburst created both
the X-ray cavities and the radio lobes, this would require that the morphology
is not fully defined by the 1.4 GHz emission. For the more likely two outburst
scenario, we use the buoyancy rise times to estimate an age for the more recent
outburst of 0.1 Gyr and use the associated PV work done by the expanding plasma
to create the X-ray cavities to estimate the outburst's energy of 10^58 ergs.
The present size and location of the large radio lobes implies that the AGN
outburst that created them happened ~0.4 Gyr ago and released ~5x10^58 ergs.
(abridged)
