CRL 618 is a well-studied pre-planetary nebula .
We have mapped its central region in continuum and molecular lines with the Submillimeter Array at 350 GHz at \sim 0 ^ { \prime \prime } _ { { } ^ { \textrm { . } } } 3 to 0 ^ { \prime \prime } _ { { } ^ { \textrm { . } } } 5 resolutions .
Two components are seen in 350 GHz continuum : ( 1 ) a compact emission at the center tracing the dense inner part of the H II region previously detected in 23 GHz continuum and it may trace a fast ionized wind at the base , and ( 2 ) an extended thermal dust emission surrounding the H II region , tracing the dense core previously detected in HC _ { 3 } N at the center of the circumstellar envelope .
The dense core is dusty and may contain mm-sized dust grains .
It may have a density enhancement in the equatorial plane .
It is also detected in carbon chain molecules HC _ { 3 } N and HCN , and their isotopologues , with higher excitation lines tracing closer to the central star .
It is also detected in CH _ { 2 } CHCN toward the innermost part .
Most of the emission detected here arises within \sim 630 AU ( 0 ^ { \prime \prime } _ { { } ^ { \textrm { . } } } 7 ) from the central star .
A simple radiative transfer model is used to derive the kinematics , physical conditions , and the chemical abundances in the dense core .
The dense core is expanding and accelerating , with the velocity increasing roughly linearly from \sim 3 km s ^ { -1 } in the innermost part to \sim 16 km s ^ { -1 } at 630 AU .
The mass-loss rate in the dense core is extremely high with a value of \sim 1.15 \times 10 ^ { -3 } M _ { \odot } yr ^ { -1 } .
The dense core has a mass of \sim 0.47 M _ { \odot } { } and a dynamical age of \sim 400 yrs .
It could result from a recent enhanced heavy mass-loss episode that ends the AGB phase .
The isotopic ratios of ^ { 12 } C/ ^ { 13 } C and ^ { 14 } N/ ^ { 15 } N are 9 \pm 4 and 150 \pm 50 , respectively , both lower than the solar values .