1. CONSTRAINING GALACTIC INFALL WITH DEUTERIUM OBSERVATIONS
kflajsflj
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
Tijana Prodanović, University of Novi Sad
Brian D. Fields, University of Illinois at Urbana Champaign
This is a false-color image of the star AE Aurigae (bright source of light slightly off center of image) embedded in a region of space containing smoke-like filaments of carbon-rich dust grains, a common phenomenon. Such dust might be hiding deuterium, an isotope of hydrogen, and stymieing astronomers' efforts to study star and galaxy formation. The FUSE satellite has surveyed the local deuterium concentration in the galaxy and found far more than expected. Because deuterium is a tracer of star and galaxy evolution, this discovery could radically alter theories about how stars and galaxy form.
CONSTRAINING GALACTIC INFALL WITH DEUTERIUM OBSERVATIONS

2. REALLY A STORY ABOUt DEUTERIUM...
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
REALLY A STORY ABOUt DEUTERIUM...
Only created in Big Bang (Epstein et al. 1976, Prodanović & Fields 2003)
All other processes destroy it
Monotonic decline from high to low z
Deuterium – a powerful tool in cosmology!
Cosmic baryometer! BBN success story
Measure of how much gas was processed in stars!

3. kflajsflj
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
BUT NOT SO SIMPLE …
Large (factor of 3!) variations of D abundance in local ISM over different lines of sight!
Both high and low D abundances found
“Resolution” to the problem? (Linsky at al. 2006)
Deuterium severely depleted onto dust!
Measure lower bound on the “true” D
“True” ISM D abundance
“True” ISM D = 85% of PRIMORDIAL!?
Almost NO GASS was PROCESSED in stars!?
recall: stars completely destroy D!
Reasonable stellar processing: ISM D = 55% of primordial

4. OR A DEUTERIUM FACELIFT …
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
OR A DEUTERIUM FACELIFT …
Deuterium must be replenished somehow
INFALL/ACCRETION OF PRISTINE GAS!
Eg. High-velocity clouds
falling on our Galaxy
some with metallicity
~10% Solar
little or no dust

5. PRIMORDIAL INFALL Changes things …
kflajsflj
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
PRIMORDIAL INFALL Changes things …
Increases ISM D abundance
Increases gas content of the Galaxy
Dilutes metal content of the Galaxy
Turns out:
Deuterium and Galactic gas fraction observations powerful constraint of the infall rate
M51: Cosmic Whirlpool Credit: S. Beckwith (STScI) Hubble Heritage Team, (STScI/AURA), ESA, NASA Explanation: Follow the handle of the Big Dipper away from the dipper's bowl, until you get to the handle's last bright star. Then, just slide your telescope a little south and west and you might find this stunning pair of interacting galaxies, the 51st entry in Charles Messier's famous catalog. Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (right), NGC The pair are about 31 million light-years distant and officially lie within the boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy in small, earthbound telescopes, this sharpest ever picture of M51 was made in January 2005 with the Advanced Camera for Surveys on board the Hubble Space Telescope.

6. How much infall deuterium needs?
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
How much infall deuterium needs?
Build a “keep it simple” model
Infall and NO outflow
Infall rate proportional to star-formation rate
Define gas mass fraction
Specify return fraction R – fraction of initiall stellar mass that is returned to ISM (follows from Initiall mass function); eg from Salpeter IMF

7. Results: Infall rate constraint
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
Results: Infall rate constraint
D vs. gas fraction
Shaded = observations
Solution must satisfy both
Allowed infall rate
Almost balances out star-formation!

8. results: Imf constRaint
kflajsflj
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
results: Imf constRaint
At late times D and gas fraction approach minimum values
Limiting curves above which no solutions for range of return fractions
Allowed only
Modern IMFs demand
At late times: for a large infall deuterium spending through stellar processing and deuterium replenishing through infall will reach some equilibrium constant value that will depend on alpha and R only, but same will be for a small infall since the all the gas will eventually be exhausted except for some small fraction continuously infalling; similarly for gas mass fraction – for large infall reaches some equilibrium, while for small infall there is no minimum value since gas fraction will go to zero.

9. CONCLUSIONS Local ISM D severely depleted onto dust
kflajsflj
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
CONCLUSIONS
Local ISM D severely depleted onto dust
Local ISM D abundance could be close to primordial
Then …
Local D and gas fraction observations demand large infall rate , close to star-formation rate
Consistent with hierarchical assembly of galaxies by accretion
Modern IMFs demand return fraction R~0.4 , but only marginally consistent with our results
Prodanovic & Fields, Journal of Cosmology and Astroparticle Physics, Issue 09, pp. 003(2008)

10. kflajsflj
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
Thank You!

11. Model: details Where D is the deuterium mass fraction defined as:
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
Model: details
Where D is the deuterium mass fraction defined as:
Taking we get:
which we can express in terms of the present gas mass fraction by using:

12. model: details – Return fraction
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
model: details – Return fraction
Approximate:
Then, define return fraction for each progenitor mass as:
To find a global return fraction must specify the IMF:
For mass ranges
and Salpeter IMF
we find return fraction
Modern IMFs are flatter in the high-mass regime → more high-mass stars → more ejecta
→ larger return fractions

13. model: details - envelope
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
model: details - envelope
For large infall where
For small infall where

14. D vs. Metal yields Freshly synthesized metals SN metal yield
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
D vs. Metal yields
Freshly synthesized metals
SN metal yield
Present reasonable estimates
consistent with large or no infall
since all curves converge.

15. bbn Abundances: SchraMM PLOT
XV National Conference of Astronomers of Serbia, October 4th 2008
Tijana Prodanović
bbn Abundances: SchraMM PLOT
Cyburt et al. (2004)