Copyright by Athena Ranice Stacy 2011 - The University of Texas at ...

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4.1 Growth of sink mass and rotational support over time. . . . . 104 4.2 Growth of sink angular momentum and rotational velocity over time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 4.3 Relative energy composition of sink-accreted particles . . . . . 110 4.4 Torque acting within the stellar disk. . . . . . . . . . . . . . . 112 4.5 Cooling and angular angular momentum loss timesscale of gas surrounding the sinks. . . . . . . . . . . . . . . . . . . . . . . 114 4.6 Evolution of stellar rotational velocities. . . . . . . . . . . . . 117 4.7 Angular momentum versus distance from center of the stars. . 120 5.1 Redshift evolution of the minihalo and streaming gas. . . . . . 135 5.2 Effect of relative streaming on redshift of primordial gas collapse.137 5.3 Effect of relative streaming on evolution of gas temperature with density. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 5.4 Effect of relative streaming on evolution of gas properties with halo mass. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 6.1 Penetration depth as a function of cosmic ray energy. . . . . . 160 6.2 Thermal evolution of primordial gas clouds at z = 20. . . . . . 163 6.3 Minimum temperature reached by the minihalo gas versus cosmic ray energy density and spectral slope. . . . . . . . . . . . 165 6.4 Thermal evolution of primordial gas clouds at z = 15. . . . . . 167 6.5 Thermal evolution of primordial gas in a minihalo at various distances from a pair-instability supernova. . . . . . . . . . . . 170 6.6 Bonnor-Ebert mass of gas within minihalos at z = 20. . . . . . 174 xiv
1.1 Motivation Chapter 1 Introduction The last century has seen great strides in our understanding of the history of the universe. From Edwin Hubble’s 1929 discovery that galaxies are receding from us (Hubble 1929), to Penzias and Wilson’s initial detection of the Cosmic Microwave Background (CMB; Penzias and Wilson 1965; Dicke et al. 1965), much evidence has led us to believe that the universe began ∼ 14 billion years ago in a Big Bang and has been expanding ever since. Observations have also revealed that we likely live in a Λ Cold Dark Matter (ΛCDM) universe, where the majority of the universe’s mass is composed of invisible dark matter (DM) instead of the baryonic matter with which we are familiar. Even more recently, we have found that matter itself is only a small portion of the total energy content of the universe, which is mostly comprised of a mysterious Dark Energy. The universe we observe today bears little resemblance to the universe in its initial stages - stars, planets, and galaxies did not arise until long after the Big Bang. How was the homogeneous early universe transformed into the highly complex state that we observe today? One of the keys is to understand the formation and properties of the first stars, the so-called Population III (or Pop III), since they likely played a crucial role in driving early cosmic evolution (e.g. Barkana and Loeb 2001; Bromm and Larson 2004; Ciardi and Ferrara 1
Page 1 and 2: Copyright by Athena Ranice Stacy 20
Page 3 and 4: New Insights into Primordial Star F
Page 5 and 6: Acknowledgments I first want to giv
Page 7 and 8: angular momentum to rotate at nearl
Page 9 and 10: 2.4.2.5 Thermodynamics of accretion
Page 11 and 12: Chapter 7. Outlook 177 Bibliography
Page 13: List of Figures 2.1 Density project
Page 17 and 18: leaving behind a neutron star or bl
Page 19 and 20: describe studies that have attempte
Page 21 and 22: CRs may therefore provide a pathway
Page 23 and 24: expected that some of the gas withi
Page 25 and 26: our numerical methodology in Chapte
Page 27 and 28: scattering is the major source of o
Page 29 and 30: portance. The reaction rates for an
Page 31 and 32: The size of the refinement levels h
Page 33 and 34: the sink a temperature and pressure
Page 35 and 36: same time, such as the fragments in
Page 37 and 38: Figure 2.2: Physical state of the c
Page 39 and 40: 2.4.2 Protostellar accretion 2.4.2.
Page 41 and 42: Despite some amount of rotational s
Page 43 and 44: Figure 2.6: Velocity field of the c
Page 45 and 46: Figure 2.7: Disk mass vs. time sinc
Page 47 and 48: Figure 2.8: Angular momentum struct
Page 49 and 50: sink tform [yr] Mfinal [M⊙] rinit
Page 51 and 52: sink (∼ 4 M⊙) that merged with
Page 53 and 54: actual final mass of the star is li
Page 55 and 56: the average temperature of all part
Page 57 and 58: disk accretion onto a primordial pr
Page 59 and 60: Figure 2.12: Impact of feedback on
Page 61 and 62: Figure 2.13: Comparison of specific
Page 63 and 64: the central core, eventually compri
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extending our simulation to later t
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that such a non-primordial origin t
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impose an upper mass limit to Pop I
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we use a ray-tracing scheme to foll
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3.2.3 Sink Particle Method When an
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convenient way to directly measure
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where the sum now extends from the
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Figure 3.1: Evolution of various pr
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ased on the prescription of Omukai
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ate found at late times in our ‘n
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Figure 3.2: Evolution of various di
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Figure 3.3: Evolution of disk mass
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Figure 3.4: Temperature versus numb
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disk mass is able to level off in d
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Figure 3.6: Projected density and t
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onto the disk. The numerical experi
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that the I-front expands as an hour
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Figure 3.8: Evolution of various H
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˙ M∗ = 3πΣν, (3.18) where ν
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the discrete nature of the gas part
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stars. We also note that, despite t
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current computational limits. If ra
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the deaths of massive stars (see Wo
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It is apparent that the angular mom
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h = 0.7. To accelerate structure fo
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acc = Lres 50 AU, where: Lres 0.5
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years, up to several dynamical time
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sp = GM∗ c2 , (4.1) s where cs is
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Figure 4.2: Left: Angular momentum
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through the disk, and the disk is e
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steadily grows for the rest of the
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Fig. 4.5 shows these timescales for
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sink B. Once on the MS, the sink A
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Figure 4.6: Evolution of stellar ro
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sink M∗(5000 yr) [M⊙] M∗(10 5
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present here, particularly if the s
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the stars grow to larger masses (se
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Here, Σ is the disk surface densit
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which has already detected GRBs at
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M⊙. They find that the specific a
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are initialized at high z with smal
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M⊙, where Nneigh 32 is the typic
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Figure 5.1: Top panels: Effective v
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Figure 5.2: Effect of relative stre
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Using cs ∝ T 1/2 results in ρ
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Figure 5.4: Evolution of gas proper
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a much smaller contribution from <
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abundances of HD, which also acts a
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first stars had very short lifetime
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of star-forming material. Here we t
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star formation, they found CR energ
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The GZK cutoff applies only to thos
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and virialization redshift zvir = 2
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and undergoes free-fall collapse. I
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β = 1 − −2 1/2 ɛ + 1 mHc2
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and where ΓCR(D) = 5 × 10 −29 e
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Figure 6.2: Thermal evolution of pr
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Figure 6.3: Minimum temperature rea
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Figure 6.4: Thermal evolution of pr
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The CR energy density can now be es
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2007). When considering realistic c
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6.3.5 Fragmentation scale As is evi
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2006). This decrease in fragmentati
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Chapter 7 Outlook Our understanding
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that Pop III stars likely experienc
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to be part of an area of scientific
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Barkana, R. and Loeb, A. (2001). In
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Bromm, V., Kudritzki, R. P., and Lo
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Daigne, F., Olive, K. A., Silk, J.,
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Gao, L., White, S. D. M., Jenkins,
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Heger, A., Woosley, S. E., and Spru
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Kratter, K. M. and Murray-Clay, R.
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Machida, M. N., Omukai, K., Matsumo
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Navarro, J. F. and White, S. D. M.
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Rollinde, E., Vangioni, E., and Oli
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Simon, M., Ghez, A. M., Leinert, C.
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Tanvir, N. R., Fox, D. B., Levan, A
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Rays, volume 576 of Lecture Notes i
Page 221 and 222:
Zatsepin, G. T. and Kuz’min, V. A
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