Overview

Hubble Telescope Analysis ofH II Regions and Planetary

Nebulae

Aaron Svoboda – The University of Northern ColoradoRobert Rubin – NASA Ames Research Center

Overview

• Background - H[II] Regions and Planetary Nebulae

• The Science Involved

• Our Work- Reduction and Analysis of Hubble Data

• Conclusion

H II Regions

• H[II] refers to singly ionized hydrogen

• The “birthplace” of stars

• Central star emits ionizing radiation

• Plasma is created through photoionization

Orion Nebula

• Stromgren Radius

• Proplyd

Planetary Nebula

• Results from a dying star with

leftover mass < 1.4 solar masses

• Former Red Giant

• White Dwarf star emits ionizing radiation

• Plasma is created through photoionization

NGC 6210 “The Turtle Nebula”

NGC 6818 “The Zorro Nebula”

NGC 2022

More than Just Pretty Pictures

• Measure electron and ion temperature

• Calculate chemical abundances

• Observing emission lines

Hubble Space Telescope Spectrographic Instruments:Acronyms Are Our Friends!!

• WFPC2

• Wide Field Planetary Camera

• High spatial coverage-Low dispersal resolution

• STIS

• Space Telescope and Imaging Spectrograph

• Low spatial coverage-High dispersal resolution

Orion Nebula

“Saturn” Nebula

Notation

• Line number refers to the wavelength of the emission line in Angstroms

• 5008 refers to a line with wavelength 5,008 Angstroms or 500.8 nanometers

Checking Instrumental Accuracy

• Take the ratio of the 5008 to 4960 emission lines

• Due to electron transitions from the same upper energy level

• Ratio is independent of gas temperature• Theoretically shown to be 2.984• Experimentally found to be 3.008• Error due to scattering

Electron Temperature vs. Position along the STIS slit

The electron temperatureis calculated using

the ratio of the 5008to 4364 emission

lines

Electron Temperature overlaid on WFPC2 Image

Average Temperature

dViNeN

dViNeNeToT

To- Average Electron Temp. Te- Local Electron Temp.

Ne - Ionic Electron Density Ni - Volumetric Ion Density

Average Electron Temperature vs. Radius

Mean-Squared Electron Temperature Variation

dViNeNoT

dViNeNoTeTt

2

2)(2

To- Average Electron Temp. Te- Local Electron Temp. Ne - Ionic Electron Density Ni - Volumetric Ion Density

Mean-Squared Electron Temperature Variation vs. Radius

Results and Conclusions

• Average temperature of O[III] is 10,146 K

• Mean-squared electron temperature variation is .0036

• Temperature across nebula found to range from 9,000 to 11,000 K

Why Do We Care?

• Provide insight into the evolution of nebulae

• Discrepancy between chemical abundances deduced from observation of lines that are collisionally excited compared with those that are due to recombination

• Large temperature variations across the nebula may explain why observations do not match theory

What’s Next?

• Density analysis

• Analysis of NGC 1976 (Orion Nebula)

• Find consistencies and contradictions in the data

Acknowledgements

I would like to express my deepest appreciation to Dr. Robert Rubin, Naman Bhatt, and Erik Shimshock as well as all of the physics faculty at UNC for making this research experience possible.