1. Nick Gnedin (The Big Brother)
Are There Fossils?
Reionization
Nick Gnedin (The Big Brother)

2. Co-starring
Massimo Ricotti
Andrey Kravtsov
Mike Irwin
Eline Tolstoy

3. Ultra-high res. simulation:
Resolving All
From z=8 to z=0
10 years?
Ultra-high res. simulation:
Gas,SF, RT, H2, etc
Local Group at z=0

4. Cosmic Paleontology See Mia’s talk for details Non-fossils Fossils
Virtual dwarfs

5. Metallicity Spread

6. Metallicity Distributions
Prediction:
~1% of stars have [Fe/H] < -2

7. Second Life Revisited

8. Draco Twins?
n ideal
n with errors
MS turn-off
Lower RGB
Upper RGB

9. CMD Cuts
MS turn-off
Lower RGB
Upper RGB
Yonsei-Yale
Padua

10. O O P P P P P O Wanna Shoot It Down? Test Not a test Abundance spread
Was claimed before they were discovered
a/Fe ratio O
MS Turnoff Spread O
~20 new faint dSph at d>200 kpc P
Was claimed before WMAP 3-year release
Existence of lilliput spheroidals P
S-process/r-process ratio P
Existence of [Fe/H]<-2,-3 stars P
zREI < 9 P

11. Conclusions Metallicity spread = age spread
Existence of reionization fossils is a plausible hypothesis: virtual galaxies formed before reionization resemble lowest mass dwarf spheroidals in almost all observable properties – is it a coincidence?
The observed spread in CMDs is consistent with the fossil hypothesis: predicted metallicity spread can mimic the age spread well.
It is just a hypothesis, there are no data that actually directly support it – the data have been simply consistent with it so far.