Proto-Planetary Nebula CRL 618 Shaping: Bullets vs Jets Bin Lin Professor Adam Frank Computational Astrophysics Group University of Rochester Summer 2011 REU
Contents Motivations & Background AstroBEAR code Dynamics of CRL 618 Results Future work 2/16
Examples of the Variety in Structure of Various PPN Clockwise: Boomerang Nebula, Calabash Nebula, Water Lily Nebula, IRAS 13208-6020, Cotton Candy Nebula, Egg Nebula. Image credit: ESA/HST , NASA 3/16
Proto-Planetary Nebulae Proto-planetary nebulae are stellar objects in transition from a star’s asymptotic giant branch (AGB) and planetary nebulae phases. AGB is the region of the Hertzsprung-Russell diagram populated by evolving low-intermediate mass stars. This is a period of stellar evolution undertaken by stars of 0.6–10 solar masses late in their lives. Planetary Nebulae: dying low-intermediate mass stars ejecting their outer layers. 4/16
Image credit: http:// www.hep.shef.a c.uk/ cartwright/ 5/16 phy111/
Open Questions We study PPNe because they are important for understanding the last stages of stellar evolution. PPNe morphologies are interesting. They come in a vast array of shapes and symmetries. What physical mechanisms are responsible for PPNe shapes? No single explanation works for every PPN. 6/16
CRL 618 ~ 200 years old Interesting object of disconnected lobes and clouds 7/16 Image credit: ESA/Hubble & NASA
AstroBEAR AstroBEAR is developed at the University of Rochester by the Computational Astrophysics Group in the Department of PAS. Since the equations of hydrodynamics are nonlinear, we use computers to solve them for us: • ρ , p, V are the gas density, thermal pressure, and flow velocity. • E=p( γ -1)+ ρ V 2 /2 is total energy. • γ =5/3 for monatomic gas. 8/16
AstroBEAR AstroBEAR is a parallelized hydrodynamic/MHD simulation code suitable for a variety of astrophysical problems. AstroBEAR is designed for 2D and 3D adaptive mesh refinement (AMR) simulations. Users write their own project modules by specifying initial conditions and continual processes. The development and implementation of AstroBEAR is a major part of the computational astrophysics group's research efforts. 9/16
Simulating CRL 618 We think that the individual narrow collimated lobes/ finger-like projections are the result of explosive launch mechanisms. We simulate and compare models of optically thin cooled (stable) jet and bullet driven into the surrounding media. Jet: a narrow beam of supersonic moving gas Bullet: a massive clump * We closely follow the works of Dennis, Timothy J., et al 2008 10/16 and Lee, Chin-Fei, et al. 2009
Computational Parameters We initialize a 3D grid of 36x12x12 in computational lengths where 1 computational length is 500 AU. A grid of 96x32x32 cells is defined with 3 levels of AMR. Thus, the simulation attains an effective resolution of 24 AU. The jets and bullets are of the same physical parameters: Density (cc) Temp (K) Velocity (kms) Ambient 1000 10 - Jet 100,000 10 400 Bullet 100,000 10 400 11/16
Initial Testing: Bullet 12/16
Initial Testing: Jet 13/16
Results Our latest setup so far… For time ~ 0, 15, 30 years 14/16
Future Work Once the latest simulations are complete, data analysis to be done: Is the gas cooling as expected? Xposition-Time graphs and Xvelocity-Time graphs Need to make emission maps so we can compare our simulations to observation. (Crucial for probing whether the fingers/lobes are jets or bullets.) 15/16
Acknowledgments Thanks: Adam Frank, Martín Huarte Espinosa, Bruce Balick, UR Computational Astrophysics Group AstroBEAR Wiki: https://clover.pas.rochester.edu/trac/astrobear/ 16/16
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