The 150 AU Structure of the Radio Continuum and the Ammonia Bipolar Outflow in CRL 618

Details The 150 AU Structure of the Radio Continuum and the Ammonia Bipolar Outflow in CRL 618 The 150 AU Structure of the Radio Continuum and the Ammonia Bipolar Outflow in CRL 618

Dec 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993apj...419..725m&link_type=abstract

Astrophysical Journal v.419, p.725

Astronomy and Astrophysics

Astronomy

18

Ism: H Ii Regions, Ism: Individual Alphanumeric: Crl 618, Ism: Jets And Outflows, Ism: Kinematics And Dynamics, Ism: Planetary Nebulae: General, Radio Continuum: Interstellar

Scientific paper

We present high angular resolution (0".096 x 0".066) observations of the radio continuum emission at 23 GHz and of the (2, 2) line of NH_{3 }toward the protoplanetary nebula CRL 618. The integrated flux density in the continuum indicates that the source has not experienced any systematic increase since 1980. The continuum emission is elongated in the east-west direction and shows an elliptical shell structure, reminiscent of an extremely young planetary nebula. While the southern part of the elliptical shell is rather uniform, the northern portion shows clumpy structure. The walls of the shell are unresolved by our 0".066 beam. The continuum structure indicates that the H II region is not isothermal, but the electron temperature increases toward the edges.
Ammonia is detected only in absorption toward the continuum source. The deepest absorption occurs at -50 km s-1, blueshifted with respect to the radial velocity of the approaching part of the expanding envelope (about -40 km s-1). The ammonia lines show a bipolar distribution with the blueshifted (radial velocities ≲ -45 km s-1) and redshifted (radial velocities ≳ -45 km s-1) absorptions found toward the eastern and western parts of the H II region, respectively. The most blueshifted gas is found at the eastern edge of the continuum source, possibly indicating that acceleration of the high-velocity gas is taking place at scales of a few 100 AU. The optical depth of the absorption lines is not uniform, but increases from the center to the western and eastern edges of the H II region. The data indicate that the ammonia absorption does not arise in the slow expanding asymptotic giant branch (AGB) envelope, but from the high-velocity molecular outflow. The NH3 fractional abundance increases by more than three orders of magnitude from 8 × 10-9 in the AGB envelope to at least 2 × 10-5 in the molecular outflow. The chemistry of NH3 in protoplanetary nebulae is briefly discussed.

Affiliated with

Also associated with

No associations

Rating

The 150 AU Structure of the Radio Continuum and the Ammonia Bipolar Outflow in CRL 618 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The 150 AU Structure of the Radio Continuum and the Ammonia Bipolar Outflow in CRL 618, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The 150 AU Structure of the Radio Continuum and the Ammonia Bipolar Outflow in CRL 618 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-785302