The 0Z Project Team

1
The 0Z Project Team

• Core group Norbert Christlieb (Hamburg), Judy
  Cohen (Caltech)
• Andy McWilliam, Steve Shectman and Ian Thompson
  (Carnegie)
• Past Present Postdocs Innocenza Busa,
  Franz-Joseph Zickgraf, Inese Ivans, Jorge
  Melendez Solange Ramirez, Torgny Karlsson
  Mattias Dehn
• Hamburg/ESO Survey Lutz Wizotski and Dieter
  Reimers
• Associates for the Keck Pilot Project of 2001 E.
  Carretta and R.Gratton
• Undergrad Amber Swenson (Caltech)
• Theoretical Support G. Wasserburg Y.Qian
• Also Model atmospheres Bob Kurucz, MOOG
  (abund. anal. Code) Chris Sneden, MAKEE (HIRES
  anal. code) Tom Barlow, atomic data NIST and
  Bob Kurucz, HIRES at Keck Steve Vogt, Jerry
  Nelson, Gerry Smith and their teams.

2
Outline/Summary Discovery of New Extreme EMP
Stars

• We have obtained mod. res. spectra of 1539
  candidate EMP stars from the HES ( 26 objects
  which turned out not to be metal poor stars)
• From this we have isolated 4 new extreme EMP
  giants with Fe/H quite a few giants and dwarfs below -3.0 dex
• Two of these are strong outliers in X/Fe for
  iron-peak elements and sometimes lighter elements
  too. Details for 3 Fe-peak outliers will be
  presented. (see ApJL published and ApJ submitted,
  Cohen et al 2007)
• NEW previous outliers were restricted to
  CNO and a elements
• We can find even modest outliers because we have
  significantly enlarged the sample of EMP stars,
  our data and analyses are quite accurate and
  homogenous.

3
Outline/Summary the Fe/H distribution for the
Galactic Halo

• Based on mod res spectra of 1504 stars and HIRES
  spectra of 90 of them, we find that the EMP tail
  of the Fe/H(HES) distribution is full of
  objects that do not belong there and are in
  general significantly more metal rich.
• Today we could do better with mod res spectra at
  eliminating the mistakes at the EMP end. We now
  know not to trust Fe/H for C-rich stars.
• SEGUE has more spectral coverage (no M dwarfs
  or QOs), and better more uniform photometry.
  This helps too.
• Our Fe/H(HES) distribution for 1500 candidates
  is identical for dwarfs and for giants,
  suggesting NO gradient of metallicity in the
  Galactic halo.
• BUT there may be differential issues between
  the calibration of Fe/H for giants versus dwarfs

4
Offset Between 0Z and First Stars (Cayrel et al)
VLT Project

• We have done a comparison and find the following
• Our Teff scale for giants is hotter. Our adopted
  reddening values are in the mean larger.
• For a given stellar spectrum and broad band
  colors, Fe/H(HIRES) Fe/H(1st Stars) 0.3
  dex
• Thus our extreme EMP stars with Fe/H would be Fe/H Stars Project
• The gf values are not an issue

5
Outlier HE1424-0241 Teff5190K, Fe/H -4.0 dex
6
Si/Fe vs Fe/H for halo stars and globular
clusters outlier HE1424-0241
7
Ca/Fe vs Fe/H for halo stars and globular
clusters, outlier HE1424-0241
8
Outlier HE0132-2429, Teff 5295K, Fe/H -3.6 dex
9
Outlier HE2344-2800, Teff 6380K, Fe/H -2.7
dex
10
Cr/Fe vs Mn/Fe for HES VMP EMP dwarfs, outlier
HE2344-2800 Teff 6380K, Fe/H -2.7 dex
11
First Abundance for Copper in Extreme EMP Stars
12
Theoreticians and modelers of SNII

• Start your CPUs
• Can you find individual SNII whose predicted
  nucleosynthesis yields match these stars ?

13
Histogram Fe/H(HES) Q1 and Q2 are identical
for giants and dwarfs Q1 , median, Q3 -2.32,
-1.91, -1.43 dwarfs,
-2.36, -1.96, -1.18 giants)
14
Fe/H(HES) EMP stars from HES, 12 objects

• HE1159-0525 -3.52 dex Fe/H(HES)
• HE1150-0428 -3.57
• HE2209-3909 -3.59
• HE1031-0020 -3.61
• HE0122-1616 -3.63
• HE0305-5442 -3.68
• HE0313-3640 -3.72
• HE0911-0512 -3.84 M dwarf
• HE2323-0256 -3.96
• HE0208-5335 -4.14 QSO
• HE10300137 -4.37 M dwarf
• HE1432-1819 -4.43
• Score so far 12 2 M dwarfs 1 QSO 9
  possible Fe/H

15
Fe/H(HES) EMP stars from HES, 12 objects

• ID Fe/H(HES)
  Fe/H(HIRES) (dex) Comments
• HE1159-0525 -3.52
  Extreme C-star
• HE1150-0428 -3.57 -3.27
  C-star
• HE2209-3909 -3.59 near MSTO,
  hot, Fe/H -3.6 dex
• HE1031-0020 -3.61 -2.88
  C-star
• HE0122-1616 -3.63 -2.8
• HE0305-5442 -3.68 -3.56 (Cayrel)
  Rediscovery CS22968-014
• HE0313-3640 -3.72 near MSTO,
  hot, Fe/H -3.6 dex
• HE0911-0512 -3.84 M dwarf
• HE2323-0256 -3.96 -3.78
  Rediscovery CS22949-037
• HE0208-5335 -4.14 QSO
• HE10300137 -4.37 M dwarf
• HE1432-1819 -4.43 -2.51

16
Effect of Using HIRES Abundances, 1565 mod res
spectra

• Of 12 stars Fe/H(HES) QSO
• 2 are rediscoveries of known EMP stars from HK
  Survey
• 4 have HIRES analysis, with Fe/H -3.5 dex
• 3 left all appear from examining mod res spectra
  not to be extreme EMP stars,
• Net result of 1555 mod res spectra NO NEW
  EXTREME EMP STARS

17
The Extreme EMP End of the Fe/H histogram with
raw Fe/H(HES) and with HIRES Fe/H substituted
when available all objects below Fe/H -3.7
dex disappear.
18
Outline/Summary Discovery of New Extreme EMP
Stars

• We have obtained mod. res. spectra of 1539
  candidate EMP stars from the HES ( 26 objects
  which turned out not to be metal poor stars)
• From this we have isolated 4 new extreme EMP
  giants with Fe/H quite a few giants and dwarfs below -3.0 dex
• Two of these are strong outliers in X/Fe for
  iron-peak elements and sometimes lighter elements
  too. Details for 3 Fe-peak outliers will be
  presented. (see ApJL published and ApJ submitted,
  Cohen et al 2007)
• NEW previous outliers were restricted to
  CNO and a elements
• We can find even modest outliers because we have
  significantly enlarged the sample of EMP stars,
  our data and analyses are quite accurate and
  homogenous.

19
Outline/Summary the Fe/H distribution for the
Galactic Halo

• Based on mod res spectra of 1504 stars and HIRES
  spectra of 90 of them, we find that the EMP tail
  of the Fe/H(HES) distribution is full of
  objects that do not belong there and are in
  general significantly more metal rich.
• Today we could do better with mod res spectra at
  eliminating the mistakes at the EMP end. We now
  know not to trust Fe/H for C-rich stars.
• SEGUE has more spectral coverage (no M dwarfs
  or QOs), and better more uniform photometry.
  This helps too.
• Our Fe/H(HES) distribution for 1500 candidates
  is identical for dwarfs and for giants,
  suggesting NO gradient of metallicity in the
  Galactic halo.
• BUT there may be differential issues between
  the calibration of Fe/H for giants versus dwarfs

20
Backup slides
21
Comparison Fe/H(HIRES) with almost up-to-date
Beers et al, still positive overall
22
Region of 4030 A Mn triplet in 3 EMP stars, the
top one is the most Fe-poor.These outliers are
REAL !
23
Histograms of Fe/H(HIRES, or HES) for giants
and dwarfs
24
Our samples are more than 90 complete for Dec
-25 deg, and are fairly complete in the south,
the Fe/H histogram is unbiased