galaxies and cosmology

Galaxies and Cosmology

5 points, vt-2007

Teacher: Göran Östlin

Lectures 7-9

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Theoretical cosmology

Problems with Newtonian Gravity and Mechanics:GravityInertial frames - absolute space and time

General Relativity - matter curves space (& time), EPG + g = -8G 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

€

ds2 = dx 2 + dy 2

ds2 = dx 2 + dy 2 + dz2

ds2 = dr2 + r2(dθ 2 + sin2θ dφ2)

ds2 = r2(dθ 2 + sin2θ dφ2)

ds2 = dx 2 + dy 2 + dz2 − c 2dt 2

ds2 < 0

ds2 = 0

ds2 > 0

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

€

ds2 = c 2dt 2 − R2(t)dr2

1− kr2+ r2(dθ 2 + sin2θ dφ2)

⎡

⎣ ⎢

⎤

⎦ ⎥

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 accurateGeneral relativistic description of space-time required

Redshift



Redshifts…



Cosmic time vs redshift

Newtonian derivation of Friedman equations(see handwritten handouts)

FRW-models, summary

Properties of the Universe set by3 parameters: m, , k of Which only 2 areIndependent: 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 withGreat luminosity and rapid variability.

Common characteristics:Broad emission lines, high excitation, jetsflat 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 Schmidtdetermines redshiftfor the first time

Compare GRBsQuickTime och en

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Seyfert spectraQuickTime och en






Broad and narrow linesPermitted and forbidden lines

Active galaxies / Active galactic nuclei (AGN)

Central enginevariability 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-raysBroad line region, dense ionised clouds, rapid movingNarrow line region, dilute ionised clouds, slower

reverbration mappingObscuring torus with dust and molecular gas,

sublimation evacuate central part -> torusRelativistic (superluminal) Jets, and radio Lobes



QSO spectrum

Note the broad emission lines and blue continuum



Radio images of radio galaxiesSynchrotron emission



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

Jets often one-sided due to relativistic beaming

F_lam vs F_lam*lam

Blazar spectra



Superluminal motionQuickTime och en




SuperluminalMotions !

QSO absorption lines



Unified AGN models

Idea: all AGN are basically the same phenomenaDiffering 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

Sex A



LeoI

Tidal drag on NGC205 from M31

Local Group





HCG31

GalaxyEvolution/Transformation

Caught inaction

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 findingclusters



Perseus cluster central galaxy

Butcher-Oemler effect, etc:

As we look back in time, the spiral fraction ofRich clusters become higher and higher (BO)

Cluster and Galaxy transformation

Interactions: galaxy mergerscluster mergergalaxy harassmentram pressure strippingdiffuse intracluster light: stars + gasvs Hot intracluster gas

Masses of clusters:Virial theorem: M = RA v

2 / 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)



Gravitational lensing









Einstein ring

Abell 2218, strong lensingcf weak lensing (statistical)



Angular distribution of Abell-clustersBrightest cluster galaxy method allows rough space distribution to be inferred

Virgo supercluster


krävs för att kunna se bilden.Bound?-Not relaxed

LargeScaleFlows



Distribution of galaxies on the sky

Sponge-like topology of universe



CfARedshiftSurveyGreat wall

Voids!

Finger of god

SDSS





Distribution of red and blue galaxies in space

Intergalactic matter



Gunn-Peterson effect



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



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Peculiar velocities

Deviations from the Hubble flow

Basic Friedmann model universa(see handout papers)

galaxies and cosmology

Documents

time space

straight line

space curvature

qsosradio galaxiesbl

rapid movingnarrow line

radio lobesqso spectrumnote

obs em em

xraysbroad line region