Early Galactic Nucleosynthesis: The Impact of HST/STIS Spectra of Metal-Poor Stars

1. Early Galactic Nucleosynthesis: The Impact ofHST/STIS Spectra of Metal-Poor Stars Chris Sneden University of Texas

2. John Cowan Jim Truran Scott Burles Tim Beers Jim Lawler IneseIvans Jennifer Simmerer CatyPilachowski Jennifer Sobeck Betsy den Hartog David Lai Scott Burles George Fuller Anna Frebel Bob Kraft Angela Bragaglia Norbert Christlieb Beatriz Barbuy Anna Marino RaffaeleGratton Jennifer Johnson George Preston Debra Burris Bernd Pfeiffer Eugenio Carretta Jackson Doll Karl-Ludwig Kratz Francesca Primas Sara Lucatello Taft Armandroff Andy McWilliam Roberto Gallino Evan Kirby Vanessa Hill Ian Roederer Christian Johnson Sloane Simmons ValentinaD’Orazi Ian Thompson Matt Alvarez A Very Collaborative Effort Definitions: [A/B] = log10(NA/NB)star – log10(NA/NB)Sun log ε(A) = log10(NA/NH) + 12.0 (spectroscopic) log N(A) = log10(NA/NSi) + 6.0 (meteoritic)

3. today two topics: • the neutron-capture elements • return to the Fe-peak the common thread: nucleosynthesis at the end of stellar lives

4. HST/STIS spectra: relevant to entire nuclide range Heaviest stable elements a.k.a 3rd neutron-capture peak Understudied lighter neutron-capture elements Fe-group elements Light elements (Be, B) http://atom.kaeri.re.kr/

5. The ultimate question? How did our Galaxy produce the solar chemical composition? SCG08 = Sneden, Cowan, & Gallino 2008, ARA&A, 46, 241

6. First discussion: n(eutron)-capture elements Most isotopes of elements with Z>30 are formed by: AZ + n A+1Z Followed by, for unstable nuclei: A+1Z A+1(Z+1) + b- H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Rf Db Sg Bh Hs Mt Uun Uuu Uub La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

7. Buildup of n-capture elements • s-process: β-decays occur between successive n-captures • r-process: rapid, short-lived neutron blast temporarily • overwhelms β-decay rates • r- or s-process element: origin in solar-system • dominated by one or the other process Rolfs & Rodney (1988)

8. A detailed look at the r- and s-process paths “s-process” element “r-process” element SCG08

9. n-capture spectra of metal-poor stars HD 122563: [Fe/H] = -2.7 Teff ~ 4750 LOW n-capture CS 22892-052: [Fe/H] = -3.1 Teff ~ 4750 HIGH n-capture

10. “r-process-rich” metal-poor stars An important abundance ratio: log e(La/Eu) = +0.6 (solar total) = +0.2 (solar r-only) = +1.5 (solar s-only) first example, HD 115444, was reported by Griffin et al. 1982 SCG08

11. why are rare earths well understood? Wisconsin lab studies: log gf and hyperfine/isotopic structure Den Hartog et al. 2003 Den Hartog et al. 2003 (well studied in literature) Lawler et al. 2000a Lawler et al. 2000b Sneden et al. 2009 Sneden et al. 2009 Sneden et al. 2009 Sneden et al. 2009 Sneden et al. 2009 Lawler et al. 2007 Lawler et al. 2006 Lawler et al. 2009 Lawler et al. 2001 Lawler et al. 2008 Lawler et al. 2004 (unstable element) Ba Hf La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 8 14 3 13 4 46 2 1 5 20 1 3 14 45 36 Sun: # transitions used in analysis 4 15 32 32 37 15 9 7 1 6 21 13 55 29 8 CS 22892-052 : # transitions used in analysis

12. n-capture compositions of well-studied r-rich stars: Così fan tutte?? lines are solar-system abundances differences from solar-system means of the differences SCG08

13. Thorium/Uranium detections promise alternate Galactic ages Frebel et al. 2007

14. leading to possible radioactive decay ages Persistent question: why is Pb usually low? U/Th ratio should be best age indicator, if both elements can be detected reliably Frebel et al. 2007

15. good abundances really confront r-process predictions Ivans et al. 2006

16. But! crucial element groups for further progress Ivans et al. 2006

17. Beyond simplest results: de-coupling of the heavy/light r-process elements ZY = 39 ZBa = 56 Johnson & Bolte 2002 See also Aoki et al. 2005, 2007

18. r-process abundance distribution variations: "normal" Roederer et al 2010

19. But various densities must contribute to r-process increasing density components decreasing density components Kratz et al. 2007

20. Niobium (Nb, Z=41): surrogate for remaining n-capture elements (and their “issues”) these are the best transitions in the most favorable detection cases Nilsson et al. 2010

21. Niobium: here is why there are difficulties All reasonably strong lines are in the vacuum UV; this is why STIS is good here Nilsson et al. 2010

22. UV spectra of 3 metal-poor giants HD 122563: [Fe/H] = -2.7 Teff ~ 4750 LOW n-capture HD 115444: [Fe/H] = -2.9 Teff ~ 4650 HIGH n-capture BD+17 3248 [Fe/H] = -2.2 Teff ~ 5200 HIGH n-capture Roederer et al 2010

23. Initial STIS exploration HD 122563: [Fe/H] = -2.7 Teff ~ 4750 LOW n-capture HD 115444: [Fe/H] = -2.9 Teff ~ 4650 HIGH n-capture CS 22892-052 [Fe/H] = -3.1 Teff ~ 4750 HIGH n-capture Cowan et al. 2005

24. Heaviest stable elements scale with Eu Again, Eu is the usual “pure” r-process element Cowan et al. 2005

25. But light n-capture elements do NOT scale with Eu Cowan et al. 2005

26. Upon further review of these same STIS data … • Points = data • Lines = syntheses: • best fit (color) • ± 0.3dex (dotted) • no element (solid) Roederer et al 2010

27. Helps “complete” the n-capture distribution Points = observations Blue line = SN ν wind Farouqi et al. 2009 Gray lines = scaled solar-system Roederer et al 2010

28. Second discussion: back to the Fe-peak McWilliam 1997

29. sharpening & extension by “First Stars” group Cayrel et al. 2004

30. elements that can be directly predicted in SNe models crucial distinction from n-capture elements: the Fe-peak element productions can actually be predicted theoretically Kobayashi et al. 2006 (following Timmes et al. 1995)

31. for some elements, all seems well Kobayashi et al. 2006 (solid line new results

32. neutral lines but for others, discomfort same predicted Cr abundances ionized lines Kobayashi et al. 2006

33. should be simple to do Fe-peak elements:their abundances >> n-capture ones

34. r-process-rich stars give false impression of # of lines in metal-poor abundance work! For Fe-peak elements #/species <10 in most cases heavy n-cap = rare-earth Fe-peak light n-cap α, etc. 3rd peak, Th

35. The reality is grim for metal-poor turnoff stars

36. AND, can you believe ANY past analysis??

37. the outcome for Bergemann et al.?

38. Comparison of low metallicity spectra in the “visible” spectral region

39. a new attack: UV STIS spectra

40. The complex UV spectrum of HD 84937

41. dotted line, no Fe; solid line, best fit dashed lines: ±0.5 dex from best fit red line, perfect agreement; other lines, deviations

42. Why is working in the UV a problem?Opacity competition: metal-poor red giant

43. Opacity competition: metal-poor turnoff star

44. A summary of our results on Fe

45. probable explanation of the abundance “dip”

46. Other Fe-peak elements: a start Or, [Co/Fe] ~ +0.3 from both of these neutral and ionized lines Bergemann 2009: [Co/Fe] = +0.18 (LTE) = +0.66 (NLTE) {probably ~+0.3 (LTE) on our [Fe/H] scale}

47. This rough cobalt estimate is not too bad … HD 84937 the red line is the [Co/Fe] trend with [Fe/H] derived by the “first stars” group (Cayrel et al. 2004)

48. work on Cr I and Cr II is underway Matt Alvarez, Chris Sneden (UT), Jennifer Sobeck (U Chicago), Betsy den Hartog, Jim Lawler (U Wisconsin)

49. Summary: • metal-poor stars hold keys to understanding Galactic nucleosynthesis • Atomic physics dictates “non-standard” wavelengths for some elements • STIS in the vacuum UV is the only choice for some poorly understood • element regimes • neutron-capture elements: observers are in the lead! • STIS is crucial for both lightest and heaviest stable elements • Fe-peak elements: theorists are in the lead! • No sane person should believe Fe-peak abundances right now • but STIS data hold promise for the near-future