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# Galaxies and Cosmology PowerPoint PPT Presentation

Galaxies and Cosmology. 5 points, vt-2007 Teacher: Göran Östlin Lectures 7-9. Theoretical cosmology. Problems with Newtonian Gravity and Mechanics: Gravity Inertial frames - absolute space and time General Relativity - matter curves space (& time), EP G +  g = -8G T / c 4

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## Galaxies and Cosmology

5 points, vt-2007

Teacher: Göran Östlin

Lectures 7-9

### Theoretical cosmology

Problems with Newtonian Gravity and Mechanics:

Gravity

Inertial frames - absolute space and time

General Relativity - matter curves space (& time), EP

G + g = -8G T / c4

G, g, T are tensors

Geometry: line element

Cosmological principle: isotropy, homogeneity

Gravity can in General Relativity be regarded as a

space curvature rather than a force

Orbit of earth a straight line in space-time

### Geometrical cosmology: Line elements

2-dim cartesian

3-dim cartesian

3-dim spherical

2-dim curved space

Special relativity

Timelike separation

Null separation (light)

Spacelike separation

### Robertson-Walker line element

Simplest 4-dim (3 space, 1 time) space that fulfills the cosmological principle

Only R(t)changes with time -> homogeneously expanding or contracting space

### Redshisfts…

z = (obs - em)/ em = obs / em - 1 =  / 

vr = z  c

z = H0  d / c =>v r= H0  d

Valid up to z  0.2

NB Special relativistic formula not more accurate

General relativistic description of space-time required

### Cosmic time vs redshift

Newtonian derivation of Friedman equations

(see handwritten handouts)

### FRW-models, summary

Properties of the

Universe set by

3 parameters:

m, , k of

Which only 2 are

Independent:

m + + k = 1

Age of universe for: closed(1), critical(2), open(3), and acellerating(4) models

Active galaxies / Active galactic nuclei (AGN)

Compact regions in the centre of galaxies with

Great luminosity and rapid variability.

Common characteristics:

Broad emission lines, high excitation, jets

flat spectral energy distribution(non thermal)

Many classses:

-Seyfert 1 & 2

-Quasars, QSOs

-Radio galaxies

-Bl Lac, Blazars

… are all the same?

Quasars 1960’s and onwards

1963 Marten Schmidt

determines redshift

for the first time

Compare GRBs

### Seyfert spectra

Broad and narrow lines

Permitted and forbidden lines

### Active galaxies / Active galactic nuclei (AGN)

Central engine

variability put limit on size: R ≤ c var

Schwarzschild radius: Rs = 2 G M / c2

Rs = size approx Uranus orbit for 109 M

Accretion allows conversion of 0.1mc2

(fusion only 0.7%)

Radiation pressure will larger than gravity if L > LEDD

Accretion disk very hot continuum source => X-rays

Broad line region, dense ionised clouds, rapid moving

Narrow line region, dilute ionised clouds, slower

reverbration mapping

Obscuring torus with dust and molecular gas,

sublimation evacuate central part -> torus

Relativistic (superluminal) Jets, and radio Lobes

QSO spectrum

Note the broad emission lines and blue continuum

Radio images of radio galaxies

Synchrotron emission

M87 (radio galaxy): jets both in optical and radio

Jets often one-sided due to relativistic beaming

F_lam vs F_lam*lam

Superluminal

Motions !

### Unified AGN models

Idea: all AGN are basically the same phenomena

Differing due to different viewing angle and scale:

Face on view: see all components: Sy1, QSO

if looking into jet: Bl Lac (Blazar)

Edge on view: see only hot torus and NLR, Sy2

Why some radio loud while others not?

Unified BH model not perfect, but nothing else works

Unified model of AGN

Unified Model

Spiral seyfert2 with radio jets

Seyfert1

### QSO evolution - where are they now?

Debate if fall off

at z>3 is real

There must be many dead QSOs around in the local universe!

### Kinematical evidence for BH in M87

+ Grav redshifted X-ray em-lines detected in Sy1’s

Relation between black hole mass and sigma of host

galaxy: a realtion between BH and Spheroid Mass

-- Black Hole doesn’t care about disk

-- Co-evolves with spheroid/bulge!

### Clusters And Large Scale Structure (chapt. 4)

M33

LeoI

Sex A

Tidal drag on NGC205 from M31

HCG31

Galaxy

Evolution/

Transformation

Caught in

action

### Rich clusters: Virgo and Comairregular vs regular

(large spiral fraction) (mostly ”early” types))

(more relaxed)

### Hot gas in clustersX-ray emitting through thermal bremsstrahlung

Efficient way of finding

clusters

Perseus cluster central galaxy

### Butcher-Oemler effect, etc:

As we look back in time, the spiral fraction of

Rich clusters become higher and higher (BO)

Cluster and Galaxy transformation

Interactions: galaxy mergers

cluster merger

galaxy harassment

ram pressure stripping

diffuse intracluster light: stars + gas

vs Hot intracluster gas

### Masses of clusters:

Virial theorem: M = RAv2 / G

- does it apply?

X-ray gas in Hydrostatic equilibrium - does it apply?

Gravitational lensing:

it does apply but only gives mass contrast

- Methods agree fairly well (factor of 2)

Einstein ring

### Abell 2218, strong lensingcf weak lensing (statistical)

Angular distribution of Abell-clusters

Brightest cluster galaxy method allows

rough space distribution to be inferred

### Virgo supercluster

Bound?

-Not relaxed

LargeScale

Flows

Distribution of galaxies on the sky

CfA

Redshift

Survey

Great wall

Voids!

Finger of god

### SDSS

Distribution of red and blue galaxies in space

### Cosmic shear

Challenging!

- Effect on each individual galaxy tiny

- Only visible through lareg and deep samples

### Measuring Clustering

- Count in cells

- 2-point corellation function

Peculiar velocities

Deviations from the

Hubble flow