Molecular Environment and an X-ray Spectroscopy of Supernova Remnant
  Kesteven 78
  We investigate the molecular environment of the Galactic supernova remnant
(SNR) Kesteven 78 and perform an XMM-Newton X-ray spectroscopic study for the
northeastern edge of the remnant. SNR Kes78 is found to interact with the
molecular clouds (MCs) at a systemic local standard of rest velocity of 81km/s.
At around this velocity, the SNR appears to contact a long molecular strip in
the northeast and a large cloud in the east as revealed in the 13CO line, which
may be responsible for the radio brightness peak and the OH maser,
respectively. The 12CO-line bright region morphologically matches the eastern
bright radio shell in general, and the SNR is consistent in extent with a CO
cavity. Broadened 12CO line profiles discerned in the eastern maser region and
the western clumpy molecular arc and the elevated 12CO J=2-1/J=1-0 ratios along
the SNR boundary may be signatures of shock perturbation in the molecular gas.
The SNR-MC association places the SNR at a kinematic distance of 4.8 kpc. The
X-rays arising from the northeastern radio shell are emitted by underionized
hot (~1.5 keV), low-density (~0.1 cm^{-3}) plasma with solar abundance, and the
plasma may be of intercloud origin. The age of the remnant is inferred to be
about 6 kyr. The size of the molecular cavity in Kes78 implies an initial mass
around 22Msun for the progenitor.
