evolution of the elements (primordial and stellar ...dbalser/ppt/dsb_nucleosynthesis...evolution of...
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Evolution of the Elements(Primordial and Stellar Nucleosynthesis)
Dana S. Balser
Corradi & Tsvetanov
Presenter
Presentation Notes
NGC6543 (Cat’s Eye): Hubble Space Telescope Advanced Camera for Surveys (HST ACS) Thermal pulses every 1500 years in AGB phase Q: Why is the evolution of the elements important? A: We are made up of elements. Carbon based. All carbon processed in stars. Interesting fact: Helium was discovered in the Sun. Helios is Greek for Sun. Important Areas: Big Bang Stellar Evolution Galaxy Formation and Evolution Focus on Light Elements
Cosmic Evolution
Presenter
Presentation Notes
VACCUM ERA Planck epoch: (10^-43 sec) limit of space-time (based on fundamental constants of Gravity, quantum mechanics, and space-time). Inflation epoch: RADIATION ERA Creation of light: conversion of vacuum to radiation energy (energy of CMB) as well as particles and antiparticles Creation of baryonic matter: net baryons created (excess of matter over antimatter) Electroweak epoch: 10^-10 sec Strong epoch: 10^-4 sec Weak decoupling: 1 sec e- e+ annihilation 5 sec Nucleosynthesis 100 sec Matter Era 10,000 years (matter decouples from the light) Matter of the universe looses less energy than light from the expansion and so it dominates the mass density.
Primordial Nucleosynthesis
2p He He Hep He H He
He n Hen He H H
He p Hproduction He
433
423
43
423
43
4
+→+
+→+
+→+
+→+
+→+
γ
γ
n He H H He p H
production He
p H H H H n H
production Tritium
H p n bottleneck Deuterium
322
32
3
322
32
2
+++
+→+
+→+
+→+
+↔+
γ
γ
γ
Be He Heproduction Be
Li H Heproduction Li
734
7
734
7
γ
γ
+→+
+→+
Presenter
Presentation Notes
As the Universe expands D is formed but is easily destroyed by photons. There is a D bottleneck initially since other elements require D to form first. Once this happens 3He and 4He can form as well as small amounts of 7Li and maybe some 7 Be. Coulomb barriers and no stable nucleii at mass 5 and 8 prevent further elements to be produced. N.B. main differences in primordial versus stellar nucleosynthesis: Time scale. Primordial nucleosynthesis lasts only a few minutes while stellar nucleosynthesis last millions of years. Neutrons. There are free neutrons in the primoridal era. Reactions. Since there are free neutrons and the conditions are different the reactions that dominate are different.
Primordial Nucleosynthesis
Burles et al. (2001)
Presenter
Presentation Notes
Nucleosynthesis 100 sec As the universe cools the quarks condense into neutrons and protons. There are fewer neutrons since they are heavier. The details of the nuclear composition depend on the baryon-to-photon ratio (eta). Plot: D and 3He are burned into 4He. So the larger eta the more processing and so D and 3He decrease with increasing eta. D gets processed faster than 3He since it is less strongly bound and has a smaller Coulomb barrier. 7Li is double valued since there are two competing reactions that produce 7Li. Most of the neutrons end up in 4He since there is no stable nucleii at mass 5 and the 4He is very stable. Also, the Coulomb barriers are too large given that the Universe is expanding. N.B. the baryon-to-photon ratio is unchanged in the standard model. That is, the number of baryons and CMB photons in a co-moving volume are unchanged. The value of the baryon-to-photon ratio at present, at recombination, and at BBN are the same.
Lyman, Balmer, … Series
Hydrogen
3He+ Hyperfine Transition
102/12 →=FS
)years300,16(s10x950.1A)cm46.3(MHz65.8665
11201
01
−−=
=ν
F=0 SingletF=1 Triplet
N=3
N=2
N=1
Presenter
Presentation Notes
Ionized transition HII regions (average abundance over the life-time of the Galaxy if gas is well mixed) PNe (local sources or sinks from stars)
4He Observations: Optical Recombination Lines
HII regions in metal poor blue compact galaxies
Izotov et al. (1999)
4He Results
Yp [mass] Reference
0.2472 (0.0012) Izotov et al. (2007)0.2474 (0.0028) Peimbert et al. (2007)0.249 (0.009) Olive & Skillman (2004)
Olive & Skillman (2004) Peimbert & Peimbert (2002)
Presenter
Presentation Notes
Peimbert (SMC): Advantages (1) No underlying absorption corrrection since ionizing stars can be removed from slit (2) Helium ionization correction factor can be estimated by observing different lines of sight (3) Different locations can be examined within the HII region (4) Smaller Te reduces the effect of collisional excitation from the metastable 2 3S level of HeI Disadvantage: (1) Larger correction for chemical evolution
7Li Observations: Resonance Line
Metal poorHalo stars
Boesgaard et al. (2005)
Presenter
Presentation Notes
Fluorescence – an excited atom returns to a lower state or the ground state with the emission of light. Resonance – the longest wavelength capable of exciting fluorescence in an atom. For H this is the first Lyman line.
7Li Results: The Spite Plateau
Log(7Li/H) + 12 Reference
2.09 (+0.19,-0.13) Ryan et al. (2000)2.37 (0.1) Melendez & Ramirez (2004)2.44 (0.18) Boesgaard et al. (2005)
Spite & Spite (1982)
Deuterium Observations: Lyman Series
Q1243+3047HS 0105+1619
Kirkman et al. (2003) O’Meara et al. (2001)
Presenter
Presentation Notes
Emission lines blend to give the undulating continuum level between 4400-5000 A. The vertical marks show the Lyman series for an absorber at z=2.526. The Lyman alpha line is at 4285 A.
Deuterium Results
Steigman (2007)
10 2.68 D/H -50.270.25- ×= +
Presenter
Presentation Notes
D/H values versus Si/H normalized relative to the Sun.
3He+ Observations: HII Regions
Bania et al. (1997)
HII Regions: M16
Presenter
Presentation Notes
Hubble Space Telescope Wide Field Planetary Camera 2 (HST WFPC2): Red – SII Green – HII Blue – OIII
3He+ Observations: PNe
Balser et al. (1997)
PNe: NGC 3242
3He Results: The 3He Plateau
Bania, Rood, & Balser (2002)-5
primordial3 10 x 0.2 1.1 He/H)( ±=
Presenter
Presentation Notes
[3He/H] = log(3He/H) – log(1.5e-5) [O/H] = log(O/H) – log(6.3e-4) Sources with crosses do not have a good measurement of 4He+/H+ and could be higher.
Cosmic Microwave Background (WMAP)
10
0007.00009.0
2
102055.00965.6
0223.0−
+−
±=
=Ω
xhb
η Spergel et al. (2006)
Presenter
Presentation Notes
The CMB alone is a good constraint to eta, the baryon-to-photon ratio. The photon density is measured by the blackbody curve. The baryon density is usually expressed in terms of h^2 but this is only because it is in terms of the critical density. That is, it does not depend on the Hubble constant. The relative amplitudes of the CMB power spectrum are sensitive to the baryon density. This is because they depend on the sound speed which is a function of density.
Primordial Abundances
Burles et al. (2001)Spergel et al. (2006)
Izotov et al. (2007)Peimbert et al. (2007)Olive & Skillman (2004)
Kirkman et al. (2003)
Bania, Rood & Balser (2002)
Ryan et al. (2000)Boesgaard et al. (2005)
Presenter
Presentation Notes
4He: optical recombination lines in metal poor blue compact galaxies. Need better than 5% measurement. Differences depend on He I emissivities, ionization corrections, corrections for temperature fluctuations, etc. D: Lyman series in the Lyman forest. Based on 5 best sources. Need to be careful of HI interlopers. 3He: hyperfine line in HII regions. Based on outer Galaxy HII region S209. 7Li: resonance line in metal poor halo stars. Based on many low metallicity stars.
Stellar Nucleosynthesis
α
ν
γ
γ
ν
+→+
+→+
>+→+
+→+
>+→+
++→+
−
+
HepLiLieBe
107BeHeHep2HeHeHe
106HepHeH p p
47
77
6743
433
532
2
KxT
KxT
Presenter
Presentation Notes
Note: the (3He,3He) (4He,2p) reaction produces a mean molecular weight that is smaller!
Evolution of 4He
Balser et al. (2010)dY/dZ = 1.5
Presenter
Presentation Notes
He/H abundance by mass (Y) versus metallicity by mass (Z). BCG: blue compact galaxies SMC: Small Magellanic Clouds S206: Galacitc HII region (optical/radio) LMC: Large Magellanic Clouds M17: Galactic HII Region Solid Lines: range of values for the primordial Y from Olive & Skillman (2004) assuming dY/dZ=1.5 (Chiappini et al. 2002) N.B. The solar photosphere does not contain lines of Noble gases (e.g. He). Their abundances can be determined in the Corona. Helium was discovered in a prominence spectrum. But the abundances vary and it is difficult to model these regions. (I assume it is too cool in the photosphere and the Noble gases have a high ionization potential.)
Evolution of Deuterium
Steigman (2007)
10 2.68 D/H -50.270.25- ×= +
Presenter
Presentation Notes
D/H values versus Si/H normalized relative to the Sun.
Evolution of Deuterium
Wood et al. (2004)Linsky et al. (2008)
16.015.019.1
)/()/( +
−≤Galactic
primordial
HDHD
Presenter
Presentation Notes
The D/H ratio can be divided into three separate regimes: 1. the local bubble which has a constant value; 2. intermediate distances that have a wide range of abundances; and 3. large distances that have smaller abundances. The theory is that dust depletion is more important over the longer distances producing smaller D/H values in the gas. The hot regions near stars will shock gas to put D back into the ISM (local bubble).
Evolution of 7Li
Spite & Spite (1982)
Presenter
Presentation Notes
7Li was measured to increase with time. Yet since 7Li is easily destroyed in stars one might expect the opposite. What process is creating 7Li?
Evolution of 7Li
Ryan et al. (2000)
Presenter
Presentation Notes
Primordial: produced in Big Bang and depleted by astration in stars at higher metallicicty. GCR: Galactic cosmic rays (spallation) nu-process: neutrino nucleosythesis occurs in shells surrounding the core in type-II supernovae. (Z,A) + nu (Z,A)* + nu’ (Z, A-1) + n + nu’ (Z-1,A-1) + p + nu’ (Z-2,A-4) + alpha + nu’
Evolution of 3He
Bania, Rood & Balser (2002)
“The 3He Problem”
Daniele Galli
Thermohaline Mixing
Cantiellop2HeHeHe 433 +→+
Presenter
Presentation Notes
See: http://www/astro.uu.nl/~cantiell/home/Thermohaline.html Thermohaline mixing is a hydrodynamic instability that arises when an unstable gradient in composition is stabilized by the gradient in temperature. Because it involves the diffusion of two different components (particles and heat) it belongs to the class of Double-Diffusive instabilities. In the oceans this instability can be found, for example, in regions where the evaporation leaves a warm layer of saltier water on top of less salty, cooler water. In this situation the saltier water can sink only after exchanging its heat excess. The optimal configuration for an efficient heat exchange requires a lot of available surface; long fingers satisfy this requirement.
Fini
Primordial Abundances
Steigman (2010)
He4 He3
Primordial Abundances
Steigman (2010)
D Li7
4He: Galactic HII Regions
Caplan et al. (2000)
Balser (2006)
HII Region: S206
Presenter
Presentation Notes
Optical: Fabry-Perot scans of S206 with a 95.4 arcsec diaphram. Radio: H87alpha-H93alpha of S206 with the GBT at 90 arcsec.
Deuterium: Galactic Anticenter
Rogers et al. 2007
Deuterium 327 MHz Hyperfine Transition
5107.01.2/ −±= xHD
Presenter
Presentation Notes
Telescope: 24 stations of fixed phased-antenna elements. Each stations is sub-array of Yagi elements that form multiple beams on the sky by phasing the individual elements in software.
Internal Gravity Waves
Charbonnel & Talon (2005)
Presenter
Presentation Notes
As shown by Talon & Charbonnel (2004) gravity waves are indeed veryefficient in dwarf stars along the plateau up to an effectivetemperature of ~6300K. There they dominate the transport of angularmomentum and should lead to a quasi-solid rotation state of thestellar radiative zones on very short time-scales. As a result thesurface Li depletion is expected to be independant of the initialangular momentum distribution in this range of effectivetemperatures. This should alleviate the difficulty encountered by theclassical rotating models which predict that a range of initialangular momenta generates a range of Li depletion and that the scatterincreases with the average Li depletion. In more massive starshowever the efficiency of the gravity waves strongly decreases andinternal differential rotation is expected to be maintained under theeffect of meridional circulation and turbulence induced by rotation PLOT Evolution of surface lithium abundance (N is the number abundance)with time for solar mass stars. The vertical extent of boxes shows therange of lithium values as observed in various galactic clusters (26~32) for stars with an effective temperature corresponding to that ofthe model T 100 K at the cluster age, plus a typical error inabundance determination. The horizontal extent corresponds to the ageuncertainty. Circles indicate abundance determinations, and trianglesdenote upper limits for individual stars. The solar value is shownwith the usual symbol R. Solid lines correspond to models includingIGWs and dashed lines to models without IGWs. Initial velocities areshown on the figure (in km/s). In the cases without IGWs, except forthe slowest rotator, lithium depletion is too strong, by orders ofmagnitude, at all ages. When included, IGWs, by changing the shape ofthe internal velocity gradients, lead to a decrease in the associatedtransport of chemicals. Lithium is then much less depleted, andpredictions account very well for the data. At all considered ages,the observed dispersion in atmospheric lithium is well explained interms of the initial velocity of each specific star. t, time in years.
Stellar Evolution of 3He: Theory
Daniele Galli
Presenter
Presentation Notes
Stars burn H on the main sequence (MS). When H is exhausted in the core the star expands into a red giant branch (RGB) star. As the He core collapses the outer layers expand. The convective envelope (CE) penetrates deep into the star. Outside the core is a shell of H which begins to burn as the core collapses. This shell moves outward and forces the CE to retreat. The CE dredges up and homogenizes material that was processed during the main sequence phase. During shell burning H 3He but not beyond (even in more massive stars). The pp chain is more important in lower mass stars than the CNO cycle. Because the pp chain is less sensitive to temperature than the CNO cycle, cores of low mass stars are free of convection while in higher mass stars convection develops and any 3He that is produced will be convected into the center of the star and destroyed. But in low mass stars 3He is not destroyed and accumulates in a broad zone outside the core. Note: the (3He,3He) (4He,2p) reaction produces a mean molecular weight that is smaller!
3-D Hydrodynamical and Nucleosynthetic Network
Eggleton et al. (2006)
Raleigh-TaylorInstability
p2HeHeHe 433 +→+
Presenter
Presentation Notes
As the convective envelope (CE) retreats the hydrogen burning shell (HBS) moves out into a region that is thought to be stable from convection. But preceding the H burning shell is a narrow region in which 3He burns: 3He(3He,2p)4He, which is unusual since the mean molecular weight decreases. This creates an inversion in the mean molecular weight gradient. Although small this inversion is hydrodynamically unstable due to the Raleigh-Taylor instability (layer of heavy fluid lies over a lighter fluid). In stellar interiors this takes the form of the convective instability which tends to render the temperature gradient adiabatic rather than to suppress the density version. The large reservoir of 3He produced during the main sequence feeds the instability. Since the 3-D model is expensive it was only run for a fraction of the stars evolution. They estimate that as the HBS moves out the 3He will be destroyed in 16 times as much mass as the hydrogen shell burns through and that this will be consistent with the observed 3He abundances. This mixing will occur regardless of variables like rotation or magnetic fields. Plot: inverse of the mean molecular weight as a function of the mass fraction (red; green (+2 MYr); blue (+4 MYr))
Thermohaline Mixing
Charbonnel & Zahn (2007)
Presenter
Presentation Notes
Charbonnel & Zhan claim that as the inverse molecular gradient builds up a double diffusive instability occurs called thermohaline convection. This was first explored in the oceans (layer of warm salt water over a layer of cold fresh water of slightly higher density). Thermohaline instability has two components of which one, the stabilizing one (temperature) diffuses faster than the other (salt), whose stratification is unstable. They use their 1-D models and a prescription of thermohaline mixing to generate abundances. Plot: Evolution of the surface abundance of 3He (mass fraction) [Fe/H] = -1.8 (blue), -1.3 (black); -0.5 (red). The arrows indication the luminosity bump. N.B., one theory is that a strong magnetic field could inhibit thermohaline mixing. A strong magnetic field (10^4 – 10^5) will stabilize the instability.
Search for 3He in Planetary Nebulae
NRAO Very Large Array
NAIC Arecibo Telescope
NRAO Green Bank Telescope
NGC 3242NGC 6543NGC 7009NGC 6826
NGC 6210NGC 6891
NGC 6572J320
VLA J320 3He+ Spectra
Balser et al. (2006)
Presenter
Presentation Notes
Plot: solid histograms are the data; dashed lines are models. The data are spatially smoothed by convolving with different beam sizes.
VLA J320 Model
Balser et al. (2006)-33 10 2 He/H ×≈
Presenter
Presentation Notes
Plot: using the AIPS task IRING to integrate over space and frequency. The flux drops at larger radii because of missing short spacing data.
GBT NGC 7009
62.1 hr integration
GBT (NGC7009 + NGC6543 + NGC6826)
180.3 hr integration
Arecibo (NGC6210 + NGC6891)
No Mixing in NGC3242
-43 10 x 5-2 He/H = 38 CC/1312 >
38 CC/1312 >
3He+ line at 8665 MHz C III] multiplet near 1908 A
38 CC/1312 >
-43 10 x 5-2 He/H =
Balser et al. (1999) Palla et al. (2002)
Presenter
Presentation Notes
CIII] multiplet: ^3P^0_1 - ^1S_0 1908.7 A ^3P^0_2 - ^1S_0 1906.7 A ^3_1/2P^0_0 - ^1_1/2S_0 1909.6 A (forbidden to 12C but not 13C since the non-zero spin)
Galactic Evolution of 3He: Theory
Steigman & Tosi (1992)
Presenter
Presentation Notes
Steigman & Tosi (1992, ApJ, 401, 150): The 3He survival fraction of (X3/X3,p) is plotted versus time for an envelope of different initial conditions for two main models. N.B., the 3He survival fraction does not include any D that burns into 3He. That is, since any D incorporated into a star is immediately burned to 3He, the initial stellar mass fraction of 3He includes D. The models 1 and 25 are taken from Tosi (1988, A&A, 197, 33). They adopt an IMF which is constant in space and time, a SFR which is related to the local gas and total mass density and decreases exponentially with time, and a GIR independent of position and varying exponentially with time. Model 1: adopts a SFR with e-folding time of 15 Gyr and constant GIR after disk formation of 1.7 solar masses per year. (Almost constant SFR.) Model 25: adopts a SFR with e-folding time of 5 Gyr and almost constant GIR after disk formation of solar masses per year. (SFR decreases with time.) The lower curves correspond to an initial X3p/X2p = 3 that is large. SFR – star formation rate IMF – initial mass function GIR – gas infall rate
Rotational Mixing in Stars
“…meridional circulation driven byinternal rotation might lead to themixing of CNO-processed material…of a red giant star.”Sweigart & Mengel (1979)
standard
mixing
Charbonnel (1995)
“…96% of low-mass stars doexperience an extra-mixing processon the RGB…”Charbonnel & do Nascimento (1998)
“…meridional circulation…does notlead to enough mixing…to explain theabundance anomalies…”Palacios et al. (2006)
Presenter
Presentation Notes
Observations of isotopic ratios like 12C/13C are consistent with the standard models of RGB after the first dredge-up (DUP). But observations of RGB stars after the luminosity bump reveal 12C/13C values that are much lower than expected. The luminosity bump occurs when the hydrogen burning shell (HBS), which is moving outward, reaches the lowest extent of the convective envelope (CE), which is now retreating. This leaves a molecular weight discontinuity or barrier at this location. This should inhibit any extra mixing between the base of the CE and the HBS. But after the luminosity bump the molecular gradients are much smoother permitting some mixing to potentially occur. Sweigart & Mengel (1979): investigated the possibility that meridional circulation might lead to mixing of CNO-processed material in RGB stars. They claimed that this could only occur after the luminosity bump and that it depends on the angular momentum distribution. Zahn (1992): proposed a description of the interaction between meridional circulation and shear turbulence, pushing forward the idea of chocking the meridional circulation by molecular gradients. Charbonnel (1995): used a simplified version of Zahn’s prescription that assumed a constant rotation velocity and the transport of angular momentum by hydrodynamical processes was not considered. Nevertheless, this explained the abundance anomalies. PLOT: Evolution of 12C/13C and 3He/H (in units of 10-4) as a function of luminosity. Model: standard evolution (solid) and extra mixing (dashed-dotted). Observations: carbon isotopic ratios in field Pop II (crosses) and globular cluster M4 (circle) are shown. The extra mixing process is efficient only after the luminosity bump (when the two models diverge). Charbonnel & do Nascimento (1998): use Hipparcos data for 191 stars to determine the 12C/13C for objects that have passed the luminosity bump. They determine extra mixing (12C/13C < 15) for 96% of these objects. Palacious et al. (2006): develop a self-consistent approach of rotational mixing in low mass stars. That is, the transport of angular momentum and of chemicals is coupled to the evolution of the star from the zero-age main sequence on. But there is not enough mixing to explain the observations.