1. In Search of More Massive Protostars
Physics TSP 2005
Lisa Torlina

2. Collective Properties & The Hertzsprung-Russell Diagram
Plot of luminosity vs temperature of star’s photosphere
Certain regions filled preferentially
stars sharing certain structure cluster together
Immensely useful:
Following stellar evolution (tracks on diagram)
Inference of mass & age

3. HR with a Twist Photospheres of stars: blackbodies
Single clearly defined temperature
Protostars:
Buried deep inside gas/dust clouds
No well-defined photosphere
Range of temperatures; spectrum broader & cooler than central source; non-constant efficiency
Protostars form deep inside dusty gas clouds such as this one

4. HR with a Twist The Solution:
Assign number representative of spectral distribution & temperature
Average out complexity, Study protostars statistically
 Mean frequency & Bolometric temperature!
Plot of Tbol vs luminosity (BLT): close relative of HR Diagram

5. More Massive Protostars & Evolution on the BLT Diagram
Done for low mass stars
Our project: where do medium & high mass protostars fit in?
Theoretically predict:
Protostars evolve from low to high Tbol (heat up, blow away gas & dust)
Luminosity: function of mass (bigger  more gPE  greater energy output)
Expect: pattern of evolution shifted up
Similar spread? Accelerated evolution – can’t detect?
Evolutionary Tracks for low mass protostars

6. Medium Mass Protostars: Source Selection & Data Analysis
Different regions of Milky way
Based on colour-colour diagram (medium mass)
IR image of source 27
IRAS, MXS, 1.2mm infrared data
Calculate bolometric temperature & luminosity (piecewise integration)
Plot BLT diagram

7. The Results!

8. The Results!
My Medium
Mass Sources
George’s Eta Carinae Sources

9. Conclusions & the Future
Selection process & mean frequency analysis successful
Occupy region just above low mass protostars – as predicted!
These objects are out there
The future?
Plot more sources, analyse statistically – further patterns may emerge
Develop theoretical models