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Ammonia Tracing in the Egg Nebula: Insights from VLA Observations

This study by Pao-Jan Chiu and Jeremy Lim focuses on the Egg Nebula (CRL2688), a proto-planetary nebula located about 1 kpc away. It examines the optical structure, 12CO molecular outflows, and traces of NH3(1,1) captured through VLA observations. Key findings include the analysis of the optical features, multiple outflows, and the kinematics of ammonia at higher angular resolution. The research distinguishes between different NH3 transitions, revealing insights into shocked molecular gas and the dynamics within the nebula, contributing to our understanding of stellar evolution.

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Ammonia Tracing in the Egg Nebula: Insights from VLA Observations

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  1. What does Ammonia trace in Egg Nebula Pao-Jan Chiu With Jeremy Lim 2003 8.27

  2. Outline • Optical Structure of the Egg Nebula • 12CO Molecular Outflows • Structure of NH3(1,1) • Observations with VLA • Results and Discussion • Summary

  3. CRL2688 - Egg Nebula Proto-Planetary nebula (PPN) Distance ~ 1 kpc Optical features bipolar lobes twin searchlight beams quasi-spherical AGB wind shocked molecular hydrogen “dust lane”

  4. Multiple Outflows in Egg nebula • 12CO trace multiple outflows. • Shocked molecular hydrogen traces lobes of polar outflow, tips of “equatorial” outflows. Arrow – axis of 12CO outflows contour – 12CO color – optical image + shocked H2

  5. NH3(1,1) in Egg nebulaEquatorial disk or central toru? • NH3(1,1) aligned with the dust lane • Kinematics suggest expansion: Expanding Disk • Spur to north? Bipolar lobes -63.5~-23.9km/s NH3(1,1) -75~ 5km/s Nguyen-Q-Rieu, A. Winnberg, V. Bujarrabal ,1986 VLA D array, beamsize 4”.3 × 3”.4 Redial velocites from -63.5 to -23.9 km/s

  6. Observations

  7. NH3(1,1) Results and Discussion Comparison of NH3(3,3) andNH3(1,1) • At higher angular resolution, structure of NH3(3,3) does not resemble disk NH3(3,3) Beamsize 4”.3 × 3”.4 Beamsize 3”.19 × 2”.51

  8. Compare with optical lobes and shocked H2 • NH3(3,3) traces higher density (~105-106) and higher temperature (~120K) than 12CO (2-1) • The four NH3(3,3) peaks are at/close to tips of 12CO outflows. • NH3(3,3) traces shocked molecular gas behind the shock front (traced by shocked molecular hydrogen) color – optical image + shocked H2 contour – NH3(3,3) contour – 12CO

  9. Shock region Shock region Shock region 12CO outflows 12CO cooling region cooling region 12CO 12CO 12CO Shocked H2 Shocked H2 Shocked H2 NH3(3,3) NH3(3,3) 12CO 12CO 12CO

  10. Compare with optical lobes and shocked H2 • NH3(3,3) traces higher density (~105-106) and higher temperature (~120K) than 12CO (2-1) • The four NH3(3,3) peaks are at/close to tips of 12CO outflows. • NH3(3,3) traces shocked molecular gas behind the shock front (traced by shocked molecular hydrogen) color – optical image + shocked H2 contour – NH3(3,3) contour – 12CO

  11. Velocity distribution in NH3 • North and east NH3(3,3) peaks are blueshifted • South and west NH3(3,3) peaks are redshifted • Kinematics of NH3(3,3) similar to 12CO outflow Contour - 12CO Color arrow - 12CO outflows NH3(3,3)

  12. Summary • Observed NH3(3,3) in Egg Nebula with VLA NH3(3,3) trace the higher density and temperature molecule gas • NH3(3,3) not consistent with expanding disk • NH3(3,3) located at/close to tips of 12CO outflows and behind the shocked molecular hydrogen gas • Kinematics of NH3(3,3) similar to 12CO outflows • NH3(3,3) traces shocked molecular gas behind the shock front (traced by shocked molecular hydrogen) • Does the “equatorial” outflows lie in the same plane; i.e., disk that is aligned with the dust lane

  13. Orientation of the Multiple “Equatorial” Outflows Two models: • Model 1. Oriented in different directions, with no common plane • Model 2. “Equatorial” Outflows lie in the plane of a “disk” aligned with the dust lane

  14. Orientation of the Multiple “Equatorial” Outflows Two models: • Model 1. Oriented in different directions, with no common plane • Model 2. “Equatorial” Outflows lie in the plane of a “disk” aligned with the dust lane Model 2 requires the “disk” to be (rapidly) rotating

  15. Thank you !!

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