BBN abundance observations Karl Young and Taryn Heilman Astronomy 5022 December 4, 2014

Introduction ●Two parameters affect abundances ○ n/p and η ●Cosmological probe sensitive to the first 20 minutes of the universe ●Predictions rely on GR and standard model so BBN probes these as well ●Gives current baryon density, Ω b0 h 2

n/p ratio = 1/7 Stiegman 2007

Heavy Element Production ●All n’s are used ●No stable isotopes at mass 5 or 8 Einstein-Online

Heavy Elements BBN lasts ~20 min Temperatures from 80 to 30 keV Dependence on η varies with species Stiegman 2007

CMB Photon ratio Observations of light element abundances match the η observationally attained by WMAP

Observations/Challenges -Astration- processing of material by stars -Many systematic uncertainties, but light elements are all observed in different ways, so uncertainties do not compound - 4 He is best observed in low metallicity HII regions in ultra low metallicity dwarf galaxies - 3 He cannot be distinctly observed extragalactically, and can only be extrapolated from our own galaxy -D needs to be observed in pristine environments, high redshift DLAs -Li is destroyed in some stars, produced in others

4 He Observational methods Elemental abundances can be observed through their spectral lines Actual optical spectrum from nearby dwarf galaxy Leo P from Skillman et al 2013 paper

4 He Observations-Why Dwarf Galaxies? -Luminosity-Metallicity Relationship -Oxygen is used as a tracer of overall heavy element content -Dwarf galaxies have lowest metallicity and are closest to primordial levels

4 He- Helium Abundance evolves with Heavy Element Abundance Helium fraction vs. oxygen fraction Olive & Steigman 1994 Helium fraction vs. oxygen fraction Olive & Steigman 1995 Helium fraction vs. oxygen fraction Skillman et al 2013

4 He-Current estimates of Y p Primordial Helium estimates: Y p = / (Aver et al 2013) Y p = / (Izotov et al 2013) Y p = / (Skillman et al 2013) Y p = / (Planck Collaboration*, Ade et al 2013)

3 He - measurements by gas clouds in the Milky Way -Atomic transitions are too similar to 4 He to measure from extragalactic sources -Difficult to determine effects of stellar processing

Deuterium- Baryometer of choice Strong dependence on η Deuterium is only destroyed in stars DLA’s at high redshift (z=2.5 to 3) are the preferred modern probes Challenges: HI spectra = D1 spectra + 82km/s shift Need 10m telescopes, high-res spectra (R~40,000) Few sources, only 10 DLAs have D1 abundances (2012) Ω b0 h 2 = ±

Observing Deuterium 3 component DLA at z = 3 Green ticks are DI Red ticks are HI Red line is fit used to calculate number densities Pettini 2012

Deuterium Results Pettini 2012

The Lithium Problem Prediction is 3x observation Reaction rates are uncertain Now known to 7.4% Lithium evolution Destroyed in massive stars Survives in low-mass stars Produced in some red giants -- poorly understood Produced by cosmic ray α-α collisions Cyburt 2008

Lithium Observations Absorption spectra of metal-poor stars in the halo and globular clusters [Li] = 12 + log(Li/H) Stiegman 2007

Constraints on η from species abundances Predictions (blue) from WMAP and observed abundances (yellow) Stiegman 2007Cyburt 2008

Conclusions -To measure primordial element abundances, the chemical evolution of the universe needs to be understood - 4 He and D are preferred tracers - 4 He, 3 He, and D agree mostly with WMAP values of η - 3 He is difficult to measure and has large uncertainties -These constrain Ω b0 h 2 = Lithium abundance conflicts with WMAP

References Olive, K., Steigman, G. ApJ : Steigman, G. Annu. Rev. Nucl. Part. Sci : Cyburt, R., Fields, B., Olive, K. JCAP v11 Pettini, M., Cooke, R. MNRAS : Olive, K., Skillman, E. ApJ : Skillman, E. et al Izotov, Y. I., Stasinska, G., Guseva, N. G., A&A 2013 v58 Aver, E. et al JCAP Ade. P, et al. Planck Collaboration, A&A Einstien-Online. 2014, Max Planck Institute.

Extra Refs. Not in presentation : more deuterium iarticle_query?1995ApJ S&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&f iletype=.pdfhttp://articles.adsabs.harvard.edu/cgi-bin/nph- iarticle_query?1995ApJ S&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&f iletype=.pdf (The deuterium abundance and nucleocosmochronology) Skillman, E. et al Annals of NY Acad. Sci. 688(1): tb43965.x/pdfhttp://onlinelibrary.wiley.com/doi/ /j tb43965.x/pdf