Exploding starsAnd the modeling of

Dwarf galaxies

http://www.spacetoday.org/images/DeepSpace/Stars/StarWR124Hubble.jpg

Dwarf GalaxiesWhat are they?

Where are they?

Why are we interested in them?

Dwarf galaxy

http://upload.wikimedia.org/wikipedia/en/a/a7/Phoenix_Dwarf.jpg

Ultra Faint DG

Dwarf GalaxiesWhat are they?

Where are they?

Why are we interested in them?

http://www.sciencecentric.com/images/news/map_milky_way_1000_1000.jpg

Dwarf GalaxiesWhat are they?

Where are they?

Why are we interested in them?

Ultra Faint DG’s

• Very recent discovery ~2005• Low luminosity and metallicity• Extreme dark:baryonic matter

ratio• Remnants of early structures in

galaxy formation• Closely linked to the first stars

(pop III)• Chemical Tagging provides

valuable information about the nature of these galaxies

Black dots: Milky Way starsBlue squares: DG starsRed stars: Ultra faint DG stars

Modeling Supernova

SN 1987A: NASA, ESA, P. Challis and R. Kirshner (Harvard-Smithsonian Center for Astrophysics)

Calculating mean yields• Using data from: papers by Nomoto et al, Woosley et

al and Chieffi et al.• Using sum of all isotopes for each element• Mean yields where calculated using numerical

integration of:

2

1

2

1

35.2

35.2)(

M

M

M

M

element

dmm

dmmmp

yield

Linear interpolation of (yield of a particular element) α M

Salpeter Initial Mass Function

SN Subroutine

• Part of a larger model of Dwarf Galaxy evolution

• Fortran subroutine to calculate yields of a certain element for a specified mass and metallicity, based on Nomoto SN/HN yields

• Using bilinear interpolation on the tabulated values

Conclusions

• The stellar models are sensitive to a range of variables

• Small changes in explosion energy and metallicity influence yields

• Abundances of odd elements are particularly influenced by the metallicity of a star

• a metallicity parameter and a HN/SN flag has been incorporated into a new stellar yield subroutine which will form part of a model of galactic chemical evolution

Acknowledgements and Refernces• Special thank you: Dr. Torgny Karlsson, for the time he spent helping me

learn some new physics.• Also thanks to Dick Hunstead for organizing the projects.

• References:• Nucleosynthesis Yields of Core-Collapse Supernovae and Hypernovae, and Galactic Chemical Evolution

Ken’ichi Nomoto, Nozomu Tominaga, Hideyuki Umeda, Chiaki Kobayashi, Keiichi Maeda,Nuclear Physics A (2006)

• NUCLEOSYNTHESIS AND EVOLUTION OF MASSIVE METAL-FREE STARSAlexander Heger, S. E. WoosleyApJ, March 21, 2008

• SN 1987A: NASA, ESA, P. Challis and R. Kirshner (Harvard-Smithsonian Center for Astrophysics)

• http://www.sciencecentric.com/images/news/map_milky_way_1000_1000.jpg

• http://www.spacetoday.org/images/DeepSpace/Stars/StarWR124Hubble.jpg

Mixing EffectsMixing effects for B=1.2

Yiel

d

Current Supernova Models

• Simulations are missing ~1051 ergs! (erg=1 × 10−7 joules)

• To compensate for this missing energy:– thermal explosion– piston– enhanced neutrino opacity

• Mixing in the star

Whole bunch of reading

Ultra Faint DG’s

• Very recent discovery ~2005• Low luminosity and metallicity• Extreme dark:baryonic matter

ratio• Closely linked to the first stars

(pop III)• Remnants of early structures in

galaxy formation• Chemical Tagging provides

valuable information about the nature of these galaxies

Black dots: Milky Way starsBlue squares: DG starsRed squares: Ultra faint DG stars