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The Early Universe by Ricardo de Ruiter

The Early Universe by Ricardo de Ruiter. The Aim. Describing the early universe by : Finding a relation between temperature and time Describing different epochs in the early universe Relating the epochs to energy and degrees of freedom. Assumptions & Density Parameters.

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The Early Universe by Ricardo de Ruiter

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  1. The EarlyUniverse by Ricardo de Ruiter

  2. The Aim • Describing the earlyuniverseby: • Finding a relationbetweentemperatureand time • Describing different epochs in the earlyuniverse • Relating the epochsto energy anddegrees of freedom

  3. Assumptions & Density Parameters • Assumptions: • Instantaneoustransitionradiationdominated era to matter dominated era • Relativistcdensity parameter , • Non-relativisticdensity parameter

  4. Matter-RadiationEquality Ratio of relativisticand non-relativistic matter: Using that at equality: As comparisonat the time of decoupling

  5. Matter Dominated Era • From and : • Sinceand, then: • Holdsfor • Or or

  6. RadiationDominated Era • From and : • Sinceand, then: • Or:

  7. Describing the (T,t)-relation Schematic plot of T(t)

  8. Describing the (T,t)-relation

  9. Timescales in the EarlyUniverse Timescalescanberelatedto energy: Different physicalmanifestations at different energies, thus time andtemperature!

  10. Degrees of Freedomand Energy – I At highertemperatures, there are muchhigherenergies: Equipartitiontheorem: internal energy proportionaltodegrees of freedom! , where.

  11. Degrees of Freedomand Energy – II

  12. Degrees of Freedomand Energy – III • Today: • 4 degrees of freedom • 100 MeV > E > 1 MeV • 12 degrees of freedom • 10 GeV > E > 100 MeV • From 106 to 12 d.o.f. • E > 10 GeV • 106 degrees of freedom

  13. Recent Observations Concerning the EarlyUniverse

  14. The Situation The Problem: Whatproblem?

  15. The Situation The Problem: Tounderstandhow the universe at large gotreionizedby the first generation of stars andgalaxies, bydetermining the abundance of thoseobjectsandrelatethemto the total UV-flux in the earlyuniverse

  16. The Situation • The Problem: • Tounderstandhow the universe at large gotreionizedby the first generation of stars andgalaxies, bydetermining the abundance of thoseobjectsandrelatethemto the total UV-flux in the earlyuniverse • What is reionization? • Why this research? • How to do this research?

  17. Earlier Research – I • First surveys: quasars • Advantages • High luminosity • Easilyobservable on the ground • Disadvantages • Total numberdropsfastbeyondz = 4(farthestknown quasar at z = 7.1) • Needtobe in the “line of fire”

  18. Earlier Research – II • Later surveys: nearinfrared (nIR) detection of z > 7 galaxiesusingLymandropout. • Lymandropoutusesthe Lymanlimit anditsredshift • Disadvantages • Extreme faintness (magnitude 28 or higher) • Difficultydistinguishing high-zgalaxiesfrommoderate-zgalaxiesandbrowndwarfs • OnlypossibleLyα is bright

  19. An alternative • The authorsusedanother way of probing the earlyuniverse: (the afterglow of) gamma rayburtsts (GRBs) • Advantages • High luminosity (opens a pathto high-zobjects) • Power lawbehaviour of the afterglow • Disadvantages • Distance (observations in nIR) • Narrowwindow of observation

  20. Data Acquisition • Six different GRBs have been analyzed • Host galaxies are found usingastrometry • “Whymeasuredistanceagain?” • Pinpointingallowsforobtainingspectra

  21. Results & Analysis – I: Star FormationRate Researchersdistilled the Star FormationRatefrom the observedgalaxies. The SFR is determinedby: (As comparison: a -10 magnitude dwarfgalaxy of , which has a approximatevalue of in the denomi-nator) Star formation is modest and seems to take place mostly in faint galaxies

  22. Results & Analysis – II: LuminosityFunctions Luminosity function: numberof galaxies over a certaininterval: , characteristicgalaxyluminosity, power-law slopeandnormalization factor. GRBs in the sampleshow The higher the redshift, the fainter the galaxiesseemtobecomeand the harder it is toobservethem!

  23. Results & Analysis – III: Probability of Detection Statistical analysis shows the probabililty of NOTdetecting a galaxy The overall probability of NOT findingall the host galaxies is 0.17. Onlyone of the six has been found with high certainty. Thisfavorsanevolvingluminosityfunction.

  24. Results & Analysis – IV: True andObserved Flux Density Statistical analysis comparestrueandobserved flux densityprobabilities. Correspondencebetween the blue and red linessuggeststhat the finding of specific GRB locationsshouldbeabletobedrawnrandomlyfrom a uniform distribution.

  25. Conclusions • From the data, onlyone host galaxy was evidentlydetected. However, the researchersconcludedthat • The majority of star formation at high redshifts takes place in small galaxiesthat are toofainttobedetected • Results • Fit a rapidly evolving luminosity function to higher redshifts • Are inconsistent with non-evolving functions • Are hung on two main assumptions • Demonstrate the potential of GRBs in determining the overall UV-flux in the early universe in order to explain reionization at large scales

  26. Questions?

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