X-ray emission from the nuclear region of Arp 220
  We present an imaging and spectral analysis of the nuclear region of the
ULIRG merger Arp 220, using deep \textit{Chandra}-ACIS observations summing up
to \(\sim 300\mbox{ ks}\). Narrow-band imaging with sub-pixel resolution of the
innermost nuclear region reveals two distinct Fe-K emitting sources, coincident
with the infrared and radio nuclear clusters. These sources are separated by 1'
(\(\sim 380\) pc). The X-ray emission is extended and elongated in the eastern
nucleus, like the disk emission observed in millimeter radio images, suggesting
starburst dominance in this region. We estimate Fe-K equivalent width \(\gtrsim
1\) keV for both sources, and observed 2-10 keV luminosities \(\sim
2\times{10}^{40}\mbox{ erg}\mbox{ s}^{-1}\) (W) and \(\sim 3 \times
{10}^{40}\mbox{ erg}\mbox{ s}^{-1}\) (E). In the 6-7 keV band the emission from
these regions is dominated by the 6.7 keV Fe \textsc{xxv} line, suggesting
contribution from collisionally ionized gas. The thermal energy content of this
gas is consistent with kinetic energy injection in the interstellar medium by
Type II SNe. However, nuclear winds from hidden AGN (\(\varv\sim 2000 \mbox{
km}\mbox{ s}^{-1}\)) cannot be excluded. The \(3\sigma\) upper limits on the
neutral Fe-K\(\alpha\) flux of the nuclear regions correspond to intrinsic AGN
2-10 keV luminosities \(< 1\times {10}^{42}\mbox{ erg}\mbox{ s}^{-1}\) (W) and
\(< 0.4\times {10}^{42}\mbox{ erg}\mbox{ s}^{-1}\) (E). For typical AGN SEDs
the bolometric luminosities are \(< 3\times {10}^{43}\mbox{ erg}\mbox{
s}^{-1}\) (W) and \(< 8\times {10}^{43}\mbox{ erg}\mbox{ s}^{-1}\) (E), and
black hole masses \(<1\times{10}^5 M_{\astrosun}\) (W) and \(< 5\times{10}^5
M_{\astrosun}\) (E) for Eddington limited AGNs with a standard 10\% efficiency.
