Galaxies and Cosmology

Galaxies and Cosmology

5 points, vt-2007

Teacher: Göran Östlin

Lecture 12

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Lecture 12 contents

• Cosmological problems

• Observational Cosmology: - Galaxy formation and evolution: from

popIII to today - Cosmological parameters:

H0, q0, Ω (bar, matter, DM), T0

• Summary of course

Problems with standard BBI. Magnetic Monopoles

What is a monopole? - magnetic chargeWhere are they?

Problems with standard BBII. Horizon problem

Problems with standard BBIII. Flatness Problem



k is independent of R and time, but Ω rapidly approaches the value 1.0 for small R

Alternatively: if k0 one would expect Ω0 << 1 or Ω0 >> 1To be compatible with todays Ω0 which is of order one, then Ω(tPlanck) must have been = 1.000…(55 zeros)..001-Enormous fine tuning!

€

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Ω−1 =k c 2

R2H 2

Problems with standard BBIV. Origin of structure

Inflation enlargesthe scale of quantumfluctuations

Microscopic

Becomes

Macroscopic

Evolution of R during inflation

What could have caused inflation?

Equation of state: p = w

Radiation: w=1/3Matter: w0

If w<-1/3 we would get acceleration i.e. Negative pressure makes gravity repulsive!

Could w be a function of time? quintessence

Problems with standard BBIV. Origin of structure

Inflation enlargesthe scale of quantumfluctuations

Microscopic

Becomes

Macroscopic

The nature of dark matter

Baryonic dark matterHot vs cold non-baryonic dark matter: e.g. Nutrinos vs WIMPs

Nature of dark energy

-Cosmological constant-Vaccuum energy-Quintessence-String/Brane theory, extra dimensions

The anthropic principle-is the universe there for us or do we exist because the universe looks like it does-Science of philosophy?

Structure/galaxy formation

The concept of Jeans mass

Gravity vs pressure,

Static medium: M > Mjeans exponential growthExpanding EdS: M > Mjeans linear growthExpanding Open universe: M > Mjeans no growth

Fluctuation spectrum:

EdS: temperature fluctuations in CMBR expectedat the 10-3 level, but only 10-5 observed

Dark matter comes to rescue!

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Δ =δ /ρ

ρ(x ) = δρ(x ) + ρ

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Δ ∝ r−(n +3)/ 2, Δ∝ M−(n +3)/ 6





Evolution of Jeans mass with scale factor with scale factor R

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observations

Numerical simulation



Hierarchical growth of structure

Galaxy formation is a continous process

Each big galaxy has had one major merger since z=1

Post-recombination evolution of the Jeans mass

Observations of the distant universe



HSTUltra Deep Field

2 weeks of exposure

Most distant galaxies at z=6

Problem: most of the light comes out in the infrared



Lookback time and age



Luminosity distance and angular size distance



Redshifting galaxies

LBGsLyaGsEROs



Closing in on the dark ages…



”Madau-plot”



Madau plot isvery sensitiveto asssumptionsabout dust



Hierarchical growth of structure

Galaxy formation is a continous process

Each big galaxy has had one major merger since z=1



Different phases of the merger of two galaxies with central supermassive black holes. From top to bottom, the individual images of the sequence show the gas of two colliding spiral galaxies. After the first encounter, they first separate again from each other, but then come together for a second encounter and subsequent coalescence. Gravity is driving gas into the centers of the galaxies and leads to the formation of extended tidal arms. As a result of the nuclear inflow, the black holes grow strongly in mass during a quasar phase. This phase lasts up to 100 million years and releases enough energy to heat the gas and to expel it into extragalactic space. At the end an elliptical galaxy remains (its stars are not shown in the image sequence) which contains almost no residual gas and hosts at its center the merged pair of supermassive black holes.

AGN feedback



JWST

Some future observational tools

ALMA, sub-mm, 64 antennae

JWST “the first light machine”6.5 m

OWL the overwhelmingly large telescope +50m

Cosmological parameters

The quest for 3 (4) numbers….

Properties of the Universe set by3 parameters: Ωm, Ω, Ωk of Which only 2 areIndependent: Ωm + Ω + Ωk = 1

CMBR fluctuations







First acoustic peak = standard rod!Height set by ΩBaryon

At larger scales: Sachs-Wolfe

Supernova IaMeasures q0

Q0 = Ω0,M/2 + Ω0,

Galaxies and Cosmology

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