3191214 Distant Universe Lecture

8/8/2019 3191214 Distant Universe Lecture

1/405

Seb Oliver

Lecture 1: Introduction

Distant Universe


2/405

Todays Topics

Course Document

Brief Introduction to Some of the Topics


3/405

Course Aims

The aim of this course is to introduce the

student to studies of the Universe at high

redshift

In particular the student will become

familiar with the observable properties of

the Universe and learn how these can beused to improve our physical understanding

of cosmology


4/405

Course ObjectivesBy the end of the course

the student should:

Understand the standard

cosmological tests

Appreciate the

dependence of these on

our understanding of

galaxy evolution

Be familiar with and be

able to manipulate some

of the fundamental

ingredients of our

theoretical models of

structure/galaxy formation

Understand many of the

basic principles of

observational cosmology Have had exposure to

some of the latest results

and debates in

observational cosmology.


5/405

Work & Assessment

Teaching activities:

18 lectures

~8 weekly discussion/exercise class Teaching and learning materials:

Textbooks

Problem sheets

Exercise sheets, model answers, lecture notes

Available on WWW


6/405

Work & Assessment

Student activities: Students are asked to hand in answers to selected

problems most weeks

to participate in classroom discussions

normal lecture attendance

To read around the subject as necessary

Feedback: Marked exercises, usually one per week. Model answers to problem sheets will be made

available for consultation via the WWW.

Student questionnaires at the end of term.


7/405

Work & Assessment

AssessmentThe assessment is based on a combination

of continuous assessment and exams asfollows:40% weekly problem sheets

60% end-of-year exam


8/405

Lecturers Contact Details

Seb Oliver

Arundel 216

[email protected]

http://astronomy.sussex.ac.uk/~sjo/

http://astronomy.sussex.ac.uk/~sjo/teach/dist.html

(01273-67) 8852 Office Hours

TBD
mailto:[email protected]://astronomy.sussex.ac.uk/~sjo/index.htmlhttp://astronomy.sussex.ac.uk/~sjo/teach/dist.htmlhttp://astronomy.sussex.ac.uk/~sjo/teach/dist.htmlhttp://astronomy.sussex.ac.uk/~sjo/index.htmlmailto:[email protected]


9/405

Main Topics

Standard Hot Big Bang Model

Classical Observational Cosmology

Galaxy Evolution

The Hunt for the First Galaxies

Background Light Structure Formation


10/405


Assumptions of Homogeneity and Isotropy

Nearly-Newton Cosmology

Equations of State

Geometry and fate of the Universe

The Early Universe


11/405

Model of theUniverse

Observational

Tests of model

Theorist

Observ

Lets Have

a look?

Spanner in the works?

Galaxies evolve.

But we alsowant to know

how galaxies

evolve

Is this how

the universe

works?


12/405



13/405

Classical Observational

Cosmology Observable Parameters

Distances

Classical Tests

The microwave background and Primordial

Abundances


14/405

Galaxy Evolution

K-Corrections

Luminosity Functions

V/Vmax test of Evolution

Passive Stellar Evolution

Number Counts The Global History of Star-Formation


15/405

Why Study Galaxy Evolution?

Initial Conditions

in the Early

Universe


16/405


Searches for Lyman a emitting galaxies

Photometric Redshifts & the UV-drop-out

technique

Distant Absorption Systems

Dusty Galaxies


17/405



18/405


19/405


20/405

The Background Light

Olbers Paradox

Background Light Components

The Extra-Galactic Source Background

The Cosmic Microwave Background

Radiation (CMBR)

Contributions to the background light

across the e/m spectrum


21/405

Background Light


22/405

Structure Formation

Gravitational Instability

Primordial Fluctuations

Modification of Fluctuations

Linear evolution

Non-Linear Evolution


23/405

Structure Formation


24/405

Seb Oliver

Lecture 2: Homogeneity & Isotropy

Distant Universe


25/405

Main Topics



Galaxy Evolution


Background Light

Structure Formation


26/405




Equations of State


The Early Universe


27/405

Copernican Principle

The earth does not occupy a special position

in the universe

This principal was possibly first formulatedby Giordano Bruno and not Copernicus, but

in any case it was a rather radical

proposition with profound implications forthe thinking of the universe at the time


28/405

Definitions

Afundamental observeris someone who is at rest with

respect to the rest of the Universe in their locality

Homogeneous: at any given time the Universe appears the

same to fundamental observers, e.g. the observers will

measure the same mean density or any other scalar

quantity

Isotropic: the Universe appears the same in all directions


29/405

Homogeneity

Homogeneous Not homogeneous


30/405

Isotropy

Isotropic at Not isotropic


31/405

Homogeneous Isotropic


32/405

Isotropy + Copernican Principal

Homogeneity

Isotropy about A

Isotropy about B


33/405

Cosmological Principle

The cosmological principle is that the

universe is isotropic and homogeneous

Equivalently is isotropic for everyfundamental observer

The cosmological principle alone can tell us

some very useful things


34/405

Cosmological Principle implies a

cosmological time The Cosmological Principal implies a

cosmologicaltime.

Since the Universe appears the same to allfundamental observers at any given time,

they can all synchronise their watches to

some event which occurs in the history ofthe Universe, thereafter all the watches

measure the same cosmological time


35/405

Cosmological Principle &

Hubbles Law

a

r r

v (a)

v (r)

P

O

1

)()()'(' avrvrv = 2

)(')'(' arvrv = 3

)()('arvarv

= 4

2,3,4 )()()( avrvarv = 5

1

CP

-v (a)


36/405


Hubbles Law

)()()( avrvarv = 5

Solution is

=

3

2

1

333231

232221

131211

)(

r

r

r

bbb

bbb

bbb

rvi.e.

which you could check by substituting e.g. 1131121111 rbrbrbv ++= into 5

including a tdependence rBrv )(),( tt = 6

now isotropy implies equation 6 must be invariant under rotation

rrv )(),( tHt = 7


37/405

Simply assuming that the universe ishomogeneous & isotropic has lead us to theconclusion that

i.e. the universe is either: Static h(t) = v = 0

Uniformly expanding h(t) > 0 Uniformly contracting h(t) < 0


Hubbles Law

rrv )(),( tHt =

H(t) is

Hubble parameter

7


38/405


Hubbles Law

rrv )(),( tHt =

x = 0 321

x = 0 21

x = 0 321

r

r

r

comoving position

proper position

scale factor

trial solution

8

9

aa

t

a

t

rx

r ==


39/405

We have gone a

long way with verylittle

to go any further we needsome physics ....

but how do we

know howH(ora)

varies with time?


40/405




Equations of State


The Early Universe


41/405

Seb Oliver

Lecture 3: Nearly-NewtonianCosmology

Distant Universe


42/405

Main Topics



Galaxy Evolution


Background Light

Structure Formation


43/405




Geometry again

Equations of State

Fate of the Universe

The Early Universe


44/405

Nearly-Newtonian Cosmology

Friedman Equation

Fluid Equation

Acceleration Equation


45/405

Friedman Equation

Birkhoffs Theorum

which states that the

gravitational fieldwithin a spherical hole

embedded within an

otherwise infinite

medium is zero


46/405

Friedman Equation

Thus in a homogenous Universe we can ignore the

matter outside a small sphere

m

r

Grav.

Pot.

Kin.

Energy.

Conservation of Energy

Mass in sphere

mGrrmU 22

3

4

2

1-= & 2

1


47/405

Friedman Equation

mGrrmU 22

3

4

2

1-= &2 6

mxGaxamU 2222382 -= &

I dont change

with time

mGxxa

am

a

U 222

2 3

82-

=

&

222

22

3

8

a

UmGxx

a

am +=

&

/a2

rearrange

22

22

3

8

amx

UG

a

a+=

&

const, -kc2

Friedman Equation

2

22

3

8

a

kcG

a

a=

&

3


48/405

Nearly-Newtonian Cosmology

Friedman Equation

Fluid Equation

Acceleration Equation


49/405

Fluid / Conservation Equation

1st Law of

Thermodynamics

Reverseable

Einsteins

4

233232

3

44 cxacxaa

t

E && +=

5


50/405

Fluid Equation

0

32

232 =++

&&&

rr

6

Fluid Equation

TdSPdVdE =+

=

=

=

&& +=

0=

+

t

VP

t

E4

5

6

465 + into

032

=

++

&&*3/a3

Fluid

Equatio

7


51/405

Acceleration / Differential

Friedman EquationFriedman Equation

2

22

3

8

a

kcG

a

a=

&3

( )

2

2

2a

aaa

a

a &&&&3

2

23

8

a

akcG&+=

032

=

++

&&7

Fluid

Equation

( ) 22

22

2

4a

kccpG

aaaa +

+-=

- rp&&&

2

2

2

2

4a

kc

c

pG

a

a

a

a+

+=

&&&

Gc

pG

a

a

3

84

2+

+-=

&&

+=

23

34

c

pG

a

arp&&

Acceleration

Equation

8


52/405

We derived the acceleration equation from

the Friedman and fluid equations

The acceleration equation has no newphysics

Thus only 2 of those 3 are independent

The acceleration equation is interesting as it

is independent of k

+=

23

3

4

c

pG

a

arp

&&

Acceleration / Differential

Friedman Equation


53/405

The Geometry of the Universe

From our Newtonian derivation wefound

We need some more GeneralRelativity to explore k more

The Geometry in GR is described bymetrics

Metrics determine the separation ofpoints


54/405

Euclidean 2-D Metrics

dx

dy

dsdsrd

dr


55/405

Euclidean 3-D Metrics

(dx2+dy2)1/2

dz

dsdsrd

dr

( ) 2222222 sin fqq drdrdrds ++=1


56/405

Minkowski metric

(dx2+dy2+dz2)1/2

dt2

ds

(222222 dzdydxdtcds ++-=

dsrd

dr

( )222222 jdrdrdtcds +-=2

3


57/405

Robertson Walker Metric

( ) 2222222 )( jdrSdrtRdtcds k+-= ( )

=

==

=

0)(k,

1)(k,sinh

1)(k,sin

r

r

r

rSk

+

= 22

2

22222

1)( jdr

kr

drtadtcds

++

= 2222

2

22222 sin

1)( fqq drdr

kr

drtadtcds

Various alternative forms

N.B. definitions

ofr are not

equivalent

between these

two forms

4a

5

64 5/6

4b

4c


58/405

Hand-waving derivation of


r

( )22222 sin jrddrRds +=

i.e. spatial part of k=1 solution

Represent 3-D spatial co-ordinates r, , by r, and thesetwo as angular spherical co-ordinates

7

4a


59/405

Hand-waving Derivation of


i.e. spatial part of k=-1 solution

To go to negative curvature set

( 22222 sin jrddrRds +=

(22222 sinh jrddrRds +=

7

8

4b

spatial part of k=0 solution is Minkowski4c


60/405

Hand-waving Derivation of

Robertson Walker MetricTo get alternative form 5 apply the co-ordinate transforms

Subs. into 7 gives k = +1 part of 5

gives k = -1 part of 5


61/405

Geometries

k = 0k = -1k = +1


62/405

Seb Oliver

Lecture 4: Equations of state andcosmological models

Distant Universe


63/405

Main Topics



Galaxy Evolution


Background Light

Structure Formation


64/405




Geometry again

Equations of State


The Early Universe


65/405

Models of the Universe

Three main things we can play with

Geometry

Density

Equation of State


66/405

Equation of State

Equation of state relates P and

Some simple equations of state we can

consider Matter, dust, galaxies

Radiation

Cosmological Constant

1

2

3


67/405

Question

[ yznzzyz

nn

n&&

11 -+=

1


68/405

Equation of State

We need to put these into the Fluid equation

032

=

++

&& Fluid

Equation

7

1

2

3

1 ( ) 01 33

=

a

tar 4

2 ( ) 01 44 =

ata

r 5

3 6

Critical Density


69/405

Critical Density

( )2

22

2

3

8

a

kcGtH

a

a-==

rp

&

3

set k = 0

( )

2

c 3

8

tH

G==W

Define

density

parameter

Friedman Equation

Critical density

22

2

23

81

aH

kc

H

G=

If > 1 then k >0If < 1 then k


70/405

Some definitions

Hubble Constant

Current time i.e.

age of the universe:

Current Density

Current Density

parameter

matter densities

radiation densities

cosmological constant

equivalent densities

Current scale


71/405

Specific Models

k= 0, matter dominated, Einstein de Sitter

k= 0, radiation dominated

k< 0,= 0, Milne Model

k< 0,> 0

k> 0

dominated


72/405

k= 0, matter dominated

Einstein de Sitter

Ga

a

3

82

=

&

3 Friedman Equation

with k= 0

3

0

2

3

8 =

&

10

2

38 = &

21

03

8 =

= dtGdaa 38

0

21 rp

tGa 3

82 0

23 =

3/2

1/3

0 382 tGa =

i.e.


73/405

k= 0, radiation dominated

Ga

a

3

82

=

&

3 Friedman Equation

with k= 0

4

0

2

3

8=

&


74/405

k= < 0, = 0

Milne Model

2

22

a

kc

a

a=

&

3 Friedman Equation

2

21

aa

a +

&

with = 0

since k< 0

k< 0, >0

2

22

3

8

a

kcG

a

a=

&

3 Friedman Equation

either matter or radiation

dominated models tend to

Milne model


75/405

k= +1, P>0

2

22

3

8

a

kcG

a

a=

&

3 Friedman Equation

222

3

8caGa = &

c2

0

c2

at some point and since

therefor collapse is

inevitable

+=

23

3

4

c

PG

a

arp

&&

Acceleration

Equation

8

if or then decreases


76/405

Matter dominated


77/405

dominated

2

22

3

8

a

kcG

a

a=

&

3 Friedman Equation

assuming is allowed to grow then eventually

dominates over

Universe expands for ever

no matter what value ofk


78/405

Models with both matter &

radiationFluid equation is modified with

( ) ( ) 011 4

4

3

m3 =

+

ataata grr

Assuming negligible conversion of

mass to radiation,

both terms must separately be zero

4 5

log

now

Matter

Domination

Rad

iationDomination


79/405

Models with both matter &

radiationHarder to solve for (t)

4

log

now

Matter

Domination

Rad

iationDomination

However we can assume that

k= 0 and either Radiation ormatter dominate

5

-dom m-dom


80/405

Combination of materials

( 40,30,m0,203

8 --L W+W+W= aaH

Gg

rp

matter dominated

radiation dominated

combination


81/405

Seb Oliver

Lecture 5: The Early Universe

Distant Universe


82/405

Main Topics



Galaxy Evolution


Background Light

Structure Formation


83/405




Geometry again

Equations of State


The Early Universe

Bl k B d


84/405

Black Body

Radiation

If the radiation is in in

thermal equilibrium

with a body theradiation exhibits a

black body spectrum

on


85/405

Black Body Radiation

de

v

c

hd

kTh 1

8)(

/

3

3 -=Planck Spectrum

Stephans Law

i.e.

We know

log

no

w

MatterDomination

RadiationDominati

log


86/405

The Hot Big Bang

It can be shown that as the Universe expands or

contracts a Planck spectrum remains a Planck Spectrum

COBE has been shown that the microwave backgroundradiation has a Planck Spectrum to an extraordinary high

degree of accuracy

It is likely therefore that the radiation had a black body

profile over the evolution of the Universe and by

implication the radiation was in thermal equilibrium with

the matter at some time in the past


87/405

COBE Background

De-coupling and Recombination


88/405

De coupling and Recombination

At some point in the past the matter (H, He)

was in thermal equilibrium with the

radiation. How?

If the gas is ionised into a plasma p & e- then

Thompson scattering would allow the

photons and electrons to interact

If susequently the temperature drops then

p+e-H (confusingly called recombination)and the interactions stop allowing the

photons to escape (de-coupling)

De-coupling and Recombination


89/405

De coupling and Recombination

p

e-

p pp

e-

e- e-

HH

H

H

H

zT

t arecombination

de-coupling

Temperature of Recombination


90/405


Mean energy of

Ionisation energy of H

Photo-Ionisation

Temperature

In fact as there are many more g than p, the T

can be lower and enough g have high enough

energies to ionize

>

TkEEn

B

exp)(gBoltzmann distribution

( )K2500

10ln93

eV6.13==

Bk

T



91/405


Detailed calculations give recombination at

Thus recombination occurred when Universe smaller by what factor

Current Temperature of the radiation in the Universe is

a b c d10

n

nation


92/405

Prior to recombination

As T drops such that pair creation processes

no longer occur then non-stable species disappear

Early in the Universe all sorts of exotic species exist

At these times photons dominate and thus i.e.

in fact

MeV2~

t

sec12/1

TkB

log n

o

w

MatterD

omination

Radiat

ionDomin


93/405


The Early Universe


94/405

t < 10-10

s T > 1015

K GUT

10

-10

< t T>10

12

Ke

+, e

-,quarks,,

+> ,

,

> ,

A t i N t / P t


95/405

Asymmetry in Neutron / Proton

RatioMass difference between n and p causes an asymmetry via

slightly easier

(requires less

energy) to

producep than n

once e+, e- annihilation occurs only neutron can decay

+=

s1013exp16.0~

t

NN

NX

pn

nn until nucleosynthesis


96/405

Nucleosynthesis


97/405

y


98/405

Main Topics



Galaxy Evolution


Background Light

Structure Formation



99/405



Distances

Classical Tests

The microwave background and Primordial

Abundances


100/405

Observable Parameters

Redshift

Hubble Constant and Hubble Parameter

Deceleration (acceleration?) parameter

Redshift z


101/405

Redshift --- z

maintaining convention that x0 is now

How do we relate z to scale factor?

Three ways

Redshift


102/405

Redshift

Redshift Balloon analogy


103/405

Redshift --- Balloon analogy

( )( )tata

z00

01 =+ l

l

n

n

Redshift R W metric


104/405

Redshift --- R-W metric

+

= 22

2

22222

1)( jdr

kr

drtadtcds5

Photons travel along paths with ds = 0

Consider a photon travelling along a path which we

choose to have d = 0

= 2

2

2

22

1

1)( kr

dr

ctadt

all constant, since dr is

co-moving coordinate

( )

( )ta

taz 00

0

1 =+l

l

n

n

R d hift E


105/405

Redshift --- Energy

Number density of particles:

in thermal equilibrium or where no interactions

photon numbers are conserved

( )( )tata

z 00

0

1 =+l

l

n

n

Energy density of particles

Hubble Constant and


106/405

Hubble Constant and

Hubble Parameter

( )

( )tata

tH&

=)(

( )( )0

00

ta

taH

&= Hubble constant can be observed

locally as we shall see later e.g. below

Hubble parameter

more difficult.....


107/405

Deceleration parameter

( )( ) [ ] [ ]

2

0

2

00

00

0 21 ttH

qttH

ta

ta---+

Taylor expansion

( ) ( )[ ] ( )[ ] ...2

1)(

2

0000 +-+-+= tttatttatata &&&

defining a deceleration parameterq0

( )( ) 200

00

1

Hta

taq

&&

( )( ) 2

00

1taq

&&


108/405

Deceleration parameter ( )2

00

0Hta

q

Recall acceleration equation

+=

23

3

4

c

pG

a

arp

&&

If p = 0

8

( )

2

c 3

8

tH

G==Wrecall too

in this case measuring q0 would thusgive us 0

( )( ) 2

00

1taq

&&


109/405


00

0Hta

q

if we have a Cosmological Constant term

if we can assume the Universe to be flat i.e.

So in the presence of a measurement ofq0 alone is insufficient

to determine some additional theoretical or observationconstraint is required


110/405

Seb Oliver

Lecture 6: Observable Parameters

Distance Measures

Distant Universe


111/405

Main Topics



Galaxy Evolution


Background Light

Structure Formation



112/405



Distances

Classical Tests The microwave background and Primordial

Abundances


113/405


Redshift

Hubble Constant and Hubble Parameter

Deceleration (acceleration?) parameter

Redshift --- z


114/405

Redshift --- z

maintaining convention that x0 is now

How do we relate z to scale factor?

Three ways

Redshift


115/405

Redshift



116/405


( )( )tata

z00

01 =+ l

l

n

n

Redshift --- R-W metric


117/405

Redshift R W metric

+

= 22

2

22222

1)( jdr

kr

drtadtcds5

Photons travel along paths with ds = 0

Consider a photon travelling along a path which we

choose to have d = 0

= 2

2

2

22

1

1)( kr

dr

ctadt

all constant, since dr is

co-moving coordinate

( )

( )ta

taz 00

0

1 =+l

l

n

n

Redshift Energy


118/405

Redshift --- Energy

Number density of particles:

in thermal equilibrium or where no interactions

photon numbers are conserved

( )( )tata

z 00

0

1 =+l

l

n

n

Energy density of particles

Hubble Constant and


119/405

Hubble Constant and

Hubble Parameter

( )

( )tata

tH&

=)(

( )( )0

00

ta

taH

&= Hubble constant can be observed

locally as we shall see later e.g. below

Hubble parameter

more difficult.....

l i


120/405

Deceleration parameter

( )( ) [ ] [ ]

2

0

2

00

00

0 21 ttH

qttH

ta

ta---+

Taylor expansion

( ) ( )[ ] ( )[ ] ...2

1)(

2

0000 +-+-+= tttatttatata &&&

defining a deceleration parameterq0

( )( ) 200

00

1

Hta

taq

&&

l i

( )( ) 2

00

1

Ht

taq

&&


121/405


00 Hta

Recall acceleration equation

+=

23

3

4

c

pG

a

arp

&&

If p = 0

8

( )

2

c 38

tHG==Wrecall too

in this case measuring q0 would thusgive us 0

D l i

( )( ) 2

00

1

Ht

taq

&&


122/405


00 Hta

if we have a Cosmological Constant term

if we can assume the Universe to be flat i.e.

So in the presence of a measurement ofq0 alone is insufficient

to determine some additional theoretical or observationconstraint is required



123/405


Cosmology Observable Parameters Distances


Abundances

Di


124/405

Distances

Redshift

Co-Moving Distance

Proper Distance Luminosity Distance

Angular-Diameter Distance

R d hif


125/405

Redshift z=0 z=z1 z=z2 z=z3

z=0

z=z1z=z

2

z=z3

C M i Di / i


126/405

Co-Moving Distance/separation

Much the easiest to work with

Once you have defined your co-movingpositions separations etc. they stay fixed!

Not directly related to measurable quantities

Since redshift is an important measure ofdistance from us to objects it is important to

see how co-moving separation relates to z

R b t W lk M t i


127/405


( ) 2222222 )( jdrSdrtRdtcds k+-= ( )

=

==

=

0)(k,

1)(k,sinh

1)(k,sin

r

r

r

rSk

+

= 22

2

22222

1)( jdr

kr

drtadtcds

++

= 2222

2

22222 sin

1)( fqq drdr

kr

drtadtcds

Various alternative forms

N.B. definitions

ofr are not

equivalentbetween these

two forms

4a

5

64 5/6

4b

4c

C i di t


128/405

Co-moving distance vsz

If we know the cosmology we can relate the

co-moving distance to the redshift using the

Robertson-Walker metric

( ) 2222222 )( jdrSdrtRdtcds k+-=

( )( )z

zz

H

cSR k

+W

-W+-W+W

=

1

11222

0

0

( )zz

dz

H

cdrR

W++

=

110

0Differential form

Intergal form

Matterdominatedmodels

P Di t

Cosmological Principle &Hubbles Law


129/405

Proper Distances

Proper sizes are related to co-

moving sizes by the scale

factor

It can be confusing to

talk ofproper distance

meaning the distancefrom us to an object

because the Universe

has expanding while the

photon travelled

The co-moving system is defined to be such that co-moving separations today are proper separations

rrv )(),( tHt =

=

=

=

=

( )zt +D

=D1

)(x

r

Warning

Distances vs Cosmologies


130/405

Proper distanceR0Skas a function of

cosmology Matter dominated, = 0

Matter & Radiation, = 0

0



131/405

It can be shown from consideration of the

derivation of redshift in the R-W metric andconsideration of the Friedman Equation formatter dominated Universes (=0)

Hence also luminosity and angular-diameterdistances (DL, DA)

Ideally measuring distances would givecosmology

( )( )zzz

HcSR k

+W-W+-W+W=

11122

2

0

000

0

0



132/405

A similar (equally nasty) expression can be

derived if radiation is also present, seehand-out sheets

If 0 an analytical expression for R0Sk is

not possible, must be determinednumerically

However

+ 20

0

02

1z

qz

H

cSR k

to second order

Again we see that geometric measures can give q0 but will not

give , unless we assume an equation of state


133/405

Luminosity Distance

Bolometric Luminosity


134/405

A major goal of astrophysics will be to explain

the energy (E) that celestial bodies emit

In physics the rate at which energy is emitted is

calledpower, P

Most of this energy is emitted as light

The rate at which celestial bodies emit energy via

lightis called bolometric luminosity (L)

Joules, J

Watts, W = J s-1

Watts, W = J s-1

Flux (Euclidean)


135/405

When one is somedistance away from a

source which emits

isotropically the

bolometric luminosityLis distributed over a

sphere

Fluxis the amount of energy per

second passing through a unit area

A E/tWatts / metre2, W m-2

Flux (Cosmological)


136/405

photons loose energy

interval between photons increases

N.B. using the co-moving distance as

we want the size of the sphere today

Luminosity Distance


137/405

Luminosity Distance

Cosmological Flux

Want this to look Euclidean

DefinedLuminosity Distance DL


138/405

Angular Diameter Distance

Angular Diameter DistanceP i f bj t


139/405

d

Proper size of an object

N.B.R(t)SknotR0Sk as we want

separation when photon emitted

( )kSR zdld 01+= jdl

Angular Diameter Distance( )


140/405

( )kSR

zdld

0

1+= j

ddlBy analogy with Euclidean

Where we have defined the angular diameter distance

Surface BrightnessW ld lik f


141/405

Surface brightness (B): Flux

per unit solid angle

independent

of distance

W m-2 sr-1B

Would like a measure of

energy per unit area on the sky

Surface Brightness and Olbers


142/405

paradox In an infinite Universe every line of sight

will eventually end on a star

Since in a Euclidean Universe the surfacebrightness is constant the night sky shouldbe as bright as a typical star e.g. the sun

However, the night sky is dark!

Possible resolution ...

Surface Brightness


143/405

Surface brightness is flux perunit solid angle

( ) 422

2

21

-+== z

dl

L

D

D

dl

LB

L

A

Independent of cosmology!

Surface Brightness and Olbers


144/405

paradox

Possible resolution ...

The surface brightness is not constant, but

decreases as (1+z)4


145/405

Seb Oliver

Lecture 7 & 8: Classic Cosmological

Tests

Distant Universe

Main Topics


146/405

Main Topics



Galaxy Evolution The Hunt for the First Galaxies

Background Light

Structure Formation



147/405

Cosmology


Distances


Abundances

Classic Cosmological Tests


148/405

Classic Cosmological Tests

Hubble Diagram

Number Counts

Tolman Test

Angular-Diameter Distance Test

Age of the Universe

The microwave Background and Primordial

Abundances

Hubble Diagram


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Cosmological model 1



Ideally choose astandard candle, i.e. a class of object

whose Luminosities do not change over cosmological time

flux(f)

Redshift (z)

Predictf(z) from DL in

cosmological model

Hubble Diagram Plots

Same information can be(m)


150/405

Same information can be

plotted in a variety of ways

flux(f)

Redshift (z)

magni

tude

Redshift (z)

DL

v=cz

Measure Dl from

ratio of flux to

Luminosity


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Hubble Diagram Not possible to find a class of fixed luminosity


152/405

Not possible to find a class of fixed luminosityobject

Usually choose a class whose luminosity in thelocal Universe depends in a known way on alimited number of other parameters

( )L+++= 321 aaaLL So measuring 1,etc. giveL

The stronger the correlation with andsmaller the dispersion the better

Hubble Diagram Measurement of reduces

the spread in standard candle

luminosities but a residual


153/405

L

uminosity(L

)

(z)

L()

luminosities, but a residual

dispersion re mains

UncertaintyinL

Uncertai

ntyinL,

knowing

Local calibration

What makes a good candle?


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What makes a good candle?

Small range of luminosities

High Luminosities

Few calibration parameters Low dispersion of calibration relation

Doesnt evolve

Hubble Diagram


155/405

Hubble Diagram

Cephid variables: is period

Spiral galaxies: is rotational velocity

Elliptical galaxies: is velocity dispersion Brightest Cluster Galaxy (BCG): iscluster X-ray temperature

Super Novae Ia: is time-constant of lightcurve

See. The Cosmological Distance Ladder (Rowan-Robinson)

or 5.3, 5.4 & 5.5 Cosmological Physics Peacock

Supernovae Hubble Diagram


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Supernovae Hubble Diagram

We will discuss this on Friday


157/405

Number Counts

Euclidean Number Counts


158/405

r

Assume a class of objects with

L which with a sensitivity farevisible to a distance r



159/405

L

++=

2

3

2,0

23

1,0 fNfNN

r

Cosmological

Number counts


160/405

Number counts

( )3

0

0

=

R

Rtnn

Co-moving volume element (all-sky):

( )[ ] ==drRzSRndVnN

k 0

2

000

4p

since we know:

we can deduceN(f)

Assume co-moving density is constant

( )[ ]3max003

4zSRn kp=

Co-moving volume

Cosmological Number counts


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Cosmological Number counts

Number density of sources:

( )3

00

3

0

0

=

=

-

R

Rn

R

Rntn

Proper volume element: ( ) 2/1223

1 kr

drdrRdV

-=

j

( ) ( ) ===0

02/12

23

002/12

23

00141

r

kr

drr

Rnkr

drdr

RndVnN p

j

since we know:

we can deduceN(f)

Assume co-moving density is constant

Measuring Number Counts


162/405

Measuring Number Counts

N (f2)

N (f1)

redsh

ift,

z

timesinc

ebeginofUniverse

Number Counts


163/405




Perform a surveys often

at different deeper fluxlimits

Log(N

>f)

Log (f)

All matter-dominated,

P=0 models have

Euclidean

Olbers Paradox again


164/405

Olber s Paradox again

Another statement of Olbers paradox says

that the Sky should be infinitely bright as in

an infinite Universe

=== dfdfdN

ffdNB

fmax

0

4p

True in a Euclidean Universe, but not in other cosmological models with

(4 converts from surfacebrightness to flux over

whole sky, f max is

brightest object in the sky)


165/405

Tolman Test

Surface Brightness


166/405

Surface brightness is flux perunit solid angle

( ) 422

2

21

-+== z

dl

L

D

D

dl

LB

L

A

Independent of cosmology!

Surface Brightness / Tolman Test


167/405

Gregory D. Wirth

Last modified: Sat Apr 19 13:13:18 1997


168/405


Angular Diameter Distance Test


169/405

g

Virtually identical to the Hubble diagram

Except instead of flux the observed

parameter is angular diameter of object Instead of luminosity the true quantity is

length, so astandard rodrather than

standard candle is required

What makes a good rod?


170/405

g

Small range of sizes

Sizes at frequencies that are observable with high

resolution

Large sizes!

Few calibration parameters

Low dispersion of calibration relation

Doesnt evolve



171/405

g

Angular - Diameter test


172/405

g

Angular - Diameter Distance test


173/405

g

Using Clusters

Angular - Diameter Distance Test


174/405

g

UsingRadio

galaxies

Angular - Diameter Distance Test


175/405

g

UsingRadio

galaxies

Age of the Universe


176/405


177/405

Age of the Universe


178/405

Age can be measure by Age of globular clusters

age of Universe > age of stars

Nuclear Cosmo-chronologyAge of Universe > age of chemicals

g

e.g. Peacock Chapter 5.

( ) ( ) ( )1

6.01

2

11

--

W+ zzHzt half way between

empty

critical

Cosmic Microwave Background

and Nucleosynthesis


179/405

and Nucleosynthesis

Nucleosynthesis


180/405

Summary Black-body CMBR and nucleosynthesis confirm big


181/405

picture but dont constrain models

Hubble Diagram assumes Luminosity of standard candle

does not depend on redshift

Number counts diagram assumes co-moving number

density of sources is constant

Angular-diameter distance assumes rods dont change

length (plus large scatter)

Age of the Universe assumes we can measure the age

accurately


182/405

Seb Oliver

Lecture 8: Classic Cosmological

Tests See Lecture 7

Distant Universe


183/405

Seb Oliver

Lecture 9: K-corrections

Distant Universe


184/405

Main Topics


185/405




Background Light

Structure Formation

Galaxy Evolution


186/405

Historically the classic tests were designed

to tell us about the cosmological models

To do so they assume populations do notevolve

Early applications of the tests to galaxies

soon showed that galaxies do evolve .

Why Study Galaxy Evolution?


187/405

Initial Conditions

in the Early

Universe

Galaxy Evolution


188/405

K-Corrections


V/Vmax test of Evolution Passive Stellar Evolution

Number Counts

The Global History of Star-Formation

K-Correction


189/405

The emission from a galaxy is observed at a

different wavelength from the one that at which it

was emitted - due to the cosmological redshift

In general one wants to compare the emissionproperties of galaxies at the same (emitted)

wavelength

The K-correction is an additional term in the fluxdensity to luminosity relationship which accounts

for this difference

Luminosities Important to draw a distinction betweenB l t i L i it


190/405

Bolometric Luminosity

LBol, Total luminosity of a galaxy, measured in W or L (or absolute

magnitudes)

Line Luminosity

e.g. LH, Total luminosity of an emission line, measured in W or L

In band power

e.g. luminosity emitted in a given wavelength interval measured in W or L (or

absolute magnitudes)

Luminosity (density)

Luminosity per unit frequency, measured in WHz-1, often quoted asLmeasured in W

LuminosityAstrophysical objects tend to emit their light


191/405

energy over a range of different frequencies, ,it is thus useful to define theLuminosity(L) to

be the energy per unit time per unit frequency

intervalWatts / Hertz, W Hz-1

Spectrum of a narrow line

Seyfert Galaxy


192/405

Seyfert Galaxy

Flux densityFlux density (f) to be the energy per unit time


193/405

per unit area per unit frequency interval

Both are often simply called flux :-(

Common to see ... Flux density (f) the energy per unit time perunit area per unit wavelength interval

Watts / metre2 / Hertz, W m-2 Hz-1

Watts / metre2 / metre, W m-3

Jansky: 1Jy = 10-26 W m-2 Hz-1

Flux density


194/405

negative because increases as decreases

Flux (Cosmological)


195/405

N.B.R0SknotRSk as photons are

distributed on a sphere with radius at

todays scales

Can be used to relates Bolometric luminosities and lineluminosities but notluminosity densities and flux densities

M82 a star forming galaxy


196/405

log

Lum

inosity

10 1001

Efstathiou et al. MNRAS submitted

Wavelength /m

Galaxies at Higher-zwavelength

If the sameobject is

seen further

away


197/405

Observed band

emitted feature

We see the

light

redshifted

at a fixed we seelight emitted from

bluer parts

Observed Frame Emitted or Rest Frame

galaxies at higher-z


198/405

Usually what we want to do is to know about the

objects properties at the emitted wavelength

[ ] ( )[ ]01 nn zLL e +=



199/405

Emitted

band ~ 1014 Hz

Observed

Band ~ 1013 Hz

Given rest-frame frequency band is

observed in a narrower band thusenergy per unit frequency increases

K-CorrectionWe want to relate the observed light to the light emitted at the


200/405

rest-frame frequencies

( )2

2

22

0 41

4 Lk D

Lz

SR

Lf

pp=+=

-

( ) ( )200 4 L

ee

D

dLdf

p

nnnn nn =

Using the same arguments

as we used to derive

We can see

we know ( ) ( ) 00 11 nnnn dzdz ee +=+=

( ) ( )[ ]( )2

0000

4

11

LD

dzzLdf

p

nnnn nn

++=

K-Correction

shift of spectrum


201/405

( ) ( )[ ]( )2

00

4

11

LD

zzLf

p

nn nn

++=

Band pass

Observed Frame Emitted or Rest Frame



202/405

Usually what we want to do is

to compare objects at the same

emitted wavelength

We can do this by assuming we

know what the spectrum of

Spectral Energy Distribution

SED i

[ ] ( )[ 01 nn zLL e +=

K-Correction

( ) ( )[ ]( )200 411

LD

zzLfp

nn nn++=


203/405

e.g. ( ) ( ) = 00LL

( )[ ] ( )

( )

+=+

0

000

11

zLzL

( ) ( )( )2

10

0 41

LD

zLf

p

nn

an

n

-+=K-correction

K-Correction in band fluxes and

magnitudesTransmission of band


204/405

g

( )zKDMm L +

+=

pc10log5

If fluxes and luminosities are expressed in magnitudes

Shape of spectrum

and band-pass

correction

Hence name:K-correction

( ) ( )[ ] ( ) dTzLDzL ++= 1

41

02

K-Correction in magnitudes


205/405

E.g.

( ) ( ) ( )zzK +--= 1log15.2 a

( ) ( )

=

0

0LL

( ) ( ) ( )[ ] ( )( ) ( )

++=

dTL

dTzLzzK

11log5.2

0

K-Correction in magnitudes


206/405

K-correction for galaxies in the

optical is usually positive

i.e. galaxies are fainter because

of this effect


207/405

Seb Oliver

Lecture 10: Luminosity Functions

Distant Universe

Main Topics


208/405




Background Light

Structure Formation

Galaxy Evolution


209/405

K-Corrections


V/Vmax test of Evolution Passive Stellar Evolution

Number Counts

The Global History of Star-Formation

The Luminosity Functions


210/405

To study galaxy evolution we need to compare

galaxies today with galaxies in the past

To perform a fair comparison we need to compare

the emitted power at the same wavelengths, henceK-corrections (Lect. 9)

We cannot observe thesame galaxy at different

times, so we must look at the statistical properties

of galaxies as populations, hence we study

luminosity functions

Luminosity FunctionsThe luminosity function characterises the number density ofgalaxies as a function of the luminosityL


211/405

Num

berDens

ity

Luminosity

Luminosity function,

usually written (L), is

defined as the co-movingnumber density (number

of objects per co-moving

volume) in some range of

luminosity (usually

logarithmic)

Luminosity Functions:

1/VA Estimator Object Too Faint


212/405

A

( ) ( )minmax11

zVzVVn

A

X-

==

Given a single object, X, visible

within some volume, VAObject

Detectable

j

1

For a number of objects i:

This 1/VA estimator is a

maximum likelihood estimator

Too

Big


1/VA Estimator


213/405

A

1

21

21

3

2121

11

VVnn

V

NNn +=+=

+=+


1/VA Estimator: zmaxObserve f and z over some area 2down to some flux

( )[ ] ( ) ( )02

01

41 n

pn nn f

z

DzL L

+=+


214/405

aObservef

andzover some area down to some flux

density limit,f,min

( )

( ) ( )

( )[ ]

++

=

zL

Lf

z

DL Li

11

4

0

00

2

n

nn

p

n

nn

can be estimated for

different galaxy

types

i.e.

&

calculated

numerically

likewise using Tfor type and for cosmology


1/VA Estimator: Vmax


215/405

( )dzdz

dzd

dVdVV 2

2

jj

==

=max

0

2

2

max

z

dzdzd

dVV

jj

Assume for simplicity that the zmax is constant acrossthe survey area, and that the survey is only limited at

zmax i.e. zmin=0, though generalisations not difficult

( )[ ] 2020 jdrdRrSRdV k=

( ) zzdz

H

cdrR

W++

=

1100

co-moving volume

Matter

dominated



216/405

Luminosity functionsare different andshould be estimatedseparately fordifferent:

Galaxy Types Ellipticals

Spirals

AGNs

Dwarfs

Emission Wavelengths -/X-ray through radio

Environments

Clusters Field

Redshifts

Evolution

Normal galaxy Types


217/405

Environment

Cluster


218/405

Environment

Field


219/405



220/405

In order to allow easy comparison between

different determinations of luminosity functions

and luminosity functions of different types it is

usual to use simple parameterisations Schecter - common for galaxies

Two-Power-Law - common for AGN

Power - Law with exponential cut-off - infraredgalaxies



221/405

Schecter Function - common for galaxies

( )***

* expL

dL

L

L

L

LLd

-

F=

a

f

Log (Luminosity)

Log((L))

*

L*

Exponential Cut-off

Power-Law slope



222/405

L

og

[(L)]

Log Luminosity

SDSS Luminosity Function

Blanton et al. 2001 AJ 121, 2358


223/405

www.sdss.org

SDSS Luminosity Function

Blanton et al. 2001 AJ 121, 2358


224/405

Parametric Evolution of



225/405

Log (Luminosity)

Log((L))

*

L*

Luminosity

Evolution

Density

Evolution

( ) ( ) ( )0,, == zLzfzL f

( ) ( )

== 0,, zzg

LzL f

Pure density evolution

Pure Luminosity

evolution




226/405

Log (Luminosity)

Log((L))

*

L*

Luminosity

Evolution

Density

Evolution

( ) ( )

== 0,, z

zg

LzL f

typical estimate of

Luminosity Function from 2dF

Quasar Survey


227/405

www.2dfquasar.org


Quasar Survey


228/405


Quasar Survey


229/405


Quasar Survey


230/405

For objects of fixed luminosity, L, in a

V/Vmax Evolution Test


231/405

j y, ,

redshift survey there is a maximum

volume in which the object could have

been seen, Vmax(zmax)

We can compare this to the volumein which the object actually was

seen: V(z)

Thus Vcould be

between 0 and Vmax

V(z) z

Vmax(zmax)

zmax

V/Vmax Evolution TestIf there was no change in co-moving

Vmax


232/405

number density V(z)

(f)

(e)

(d)(c)

(b)

(a)

05.0

5050

50

1

3

23

32

max/

/

.

.

.

VV =

Since the number density does

not change theprobability of

an object appearing in a

survey volume V, P(


233/405

V(z)

( ) 2/1max

125.0-

= nV

V

max

y

and it can be shown that in the absence of evolution

Thus a measured value of that differed significantly

from 0.5 demonstrates that evolution has occurred

galaxies more numerous in past

galaxies less numerous in past


234/405

Seb Oliver

Lecture 11: Luminosity Functions

V/Vmax & Morphological Evolution

Distant Universe

Main Topics


235/405



Galaxy Evolution


Background Light

Structure Formation

Galaxy Evolution


236/405

K-Corrections



Morphological Evolution





237/405

L

og

[(L)]

Log Luminosity




238/405

Log (Luminosity)

Log((L))

*

L*

Luminosity

Evolution

Density

Evolution

( ) ( ) ( )0,, == zLzfzL f

( ) ( )

== 0,, zzg

LzL f

Pure density evolution

Pure Luminosity

evolution




239/405

Log (Luminosity)

Log((L))

*

L*

Luminosity

Evolution

Density

Evolution

( ) ( )

== 0,, zzg

LzL f

typical estimate of


Quasar Survey


240/405

www.2dfquasar.org


Quasar Survey


241/405


Quasar Survey


242/405


Quasar Survey


243/405

For objects of fixed luminosity, L, in a

V/Vmax Evolution Test


244/405

redshift survey there is a maximum

volume in which the object could have

been seen, Vmax(zmax)

We can compare this to the volumein which the object actually was

seen: V(z)

Thus Vcould be

between 0 and Vmax

V(z) z

Vmax(zmax)

zmax

V/Vmax Evolution TestIf there was no change in co-moving

b d i

Vmax

V(z)


245/405

number density

(f)

(e)

(d)(c)

(b)

(a)

05.0

5050

50

1

3

23

32

max/

/

.

.

.

VV =

Since the number density does

not change theprobability of

an object appearing in a

survey volume V, P(


246/405

( ) 2/1max

125.0-

= nV

V

and it can be shown that in the absence of evolution

Thus a measured value of that differed significantly

from 0.5 demonstrates that evolution has occurred

galaxies more numerous in past

galaxies less numerous in past


247/405

MorphologicalEvolution

http://star-www.st-and.ac.uk/~spd3/hdf/hdf.html

Morphological Evolution z~0.09


248/405

Morphological Evolution 0.36


249/405



250/405



251/405



252/405



253/405



254/405


255/405



256/405



257/405



258/405



259/405



260/405



261/405



262/405



263/405



264/405

MorphologicalEvolution

Summary


265/405

Summary


Summary


266/405

Morphological

redshift distributions

are shown for

I=22.5,23.5,24.5,25.

5. the panels from

left to

right are: Total,

E/S0, Sabc, Sd/Irr


The Butcher Oemler Effect


267/405

The Butcher Oemler EffectClusters at low redshift have many more red

galaxies than blue galaxies, at higher redshiftsthe clusters have a higher fraction of bluegalaxies

The morphology Density RelationshipThe denser regions of clusters have a higher

proportion of red galaxies than the less denseregions

Environment

Cluster


268/405


269/405



270/405



271/405



272/405



273/405


Read Dressler et al 1997 ApJ 490 677 (D) use ADS or


274/405

Read Dressler et al. 1997 ApJ 490, 677 (D), use ADS or

astro-ph/9707232

How does morphology density relationship evolve?

Is this paper consistent with Butcher Oemler effect?


275/405

Seb Oliver

Lecture 12: Passive Evolution,

Number counts

Distant Universe

Main Topics



276/405



Galaxy Evolution


Background Light

Structure Formation


277/405

Passive Evolution

Galaxy Evolution

K-Corrections


278/405

K Corrections






Passive Evolution


279/405

Passive Evolution

Stellar evolution is relatively well


280/405

Stellar evolution is relatively well

understood both observationally and

theoretically

Massive stars are very hot and blue

Massive stars are very luminous

Massive stars have very short lives

Live fast die young!

Passive Evolution - Stellar Synthesis

Stellar theory predicts the evolution or (stellar


281/405

Stellar theory predicts the evolution or (stellatracks) or stars of a given mass

Observations give us libraries of stellar spectra asa function of age, mass etc.

If we know the distribution star masses producedwhen star-formation occurs - the initial mass

function - we can predict the evolution and finalspectrum and colours of the whole region or

galaxy

Passive Evolution - Stellar Synthesis

N(m)

Initial Mass-function

SFR(t)

Star-formation Rate


282/405

m

N

t

SF

Stellar Tracks

Spectral Libraries

t

SFR(t)

Star-formation RateEvolution of light froma collection of stars

born in a single burst


283/405

Wavelength / nm

Lum

inosityperu

nitmass

Ultra Violet Optical

t

Passive Evolution - Single Burst

Single Burst of Star-formation


284/405

g Galaxy starts of very blue as the light is dominated by the

massive hot blue stars

After the burst the massive stars live only a short time and

soon the light of the galaxy as a whole is dominated by thered light of the less massive, longer lived stars

Galaxy gets redder with age

Even a nave picture of the evolution of the Universe inwhich galaxies switched on at some early epoch would

predict some evolution of galaxies (all galaxies would nowbe red)

Passive Evolution More complicated star formation histories

can be imagined as a series of instantanious


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can be imagined as a series of instantaniousbursts

An exponential star-formation rate fits

many galaxies wellt

S

FR(t)

Star-formation Rate

t

t

Mexp

t is time since start of star-formation

is time-scale

Passive EvolutionThe spectra of present day

elliptical galaxies are well fit

with


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t

t

Mexp

t ~ 15 Gyr and ~ 1Gyr

The spectra of present day

spiral galaxies are well fit witht ~ 15 Gyr and ~ 3-10 Gyr

Irregular galaxies are often well fit by constant star-formation rates


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Number Count Models

Galaxy Evolution

K-Corrections


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Number Counts


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Current thinking on the basis of

number counts is that bluer

galaxies with an intrinsically

lower luminosity were more

numerous in the past

Euclidean Number CountsAssume a class of objects with

L which with a sensitivity fare

visible to a distance r


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r


L++=

23

2,02

3

1,0 fNfNN


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r


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Number counts as a test of

Cosmology


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Modelling Number CountsIngredients:

REvolutionary rate


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z

SFR

Num

be

rDens

ity

Luminosity

Wavelength

Lum

inos

ity


Spectral Energy Distributions

Evolutionary rate

Modelling Number Counts

( ) ( ) =>L

z

dLdVLfNmax

f


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( ) ( ) => LdVLfN0 0

f

( ) ( ) => T:Types 0 0maxL z

TL

dL

dVLfN f

recall

Thus can predictN(f) at various wavelengths

aim is to find a model that fits all observed counts

A no-evolution model would have (L) constant

Sophisticated models might include passive

Number Counts


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Current thinking on the basis of

number counts is that bluer

galaxies with an intrinsically

lower luminosity were more

numerous in the past


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ISO 15micron counts


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Number of galaxies

15m


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Serjeant, Oliver et al. 2000 MNRAS

Different components to models

include:starburst galaxies

normal galaxies

Seyfert galaxies

Proto-spheroidsetc....

15 micron counts


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Mid IR surveys


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NoEvo

lutionr

ange

Elbaz et al 1999, A&A 351L, 37

Open Stars: Lens fields

Open circles: HDF North field

Filled circles: HDF south field

Open squares/cross: IGTES ultra-deep

Stars/open triangles: IGTES, Deep

Filled triangles: IGTES, shallow

Radio Counts


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Modelling Number Counts

Currently there is no single models thatsuccessfully predict the number counts across all


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successfully predict the number counts across allwavelengths

Even over limited wavelength regions optical and

Near Infrared Mid Infrared

Far Infrared

Radio

Xray

There is no consensus on a best model


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Main Topics



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Galaxy Evolution


Background Light

Structure Formation

Galaxy Evolution

K-Corrections


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Global History of Star-formation

Galaxy Evolution

K-corrections


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Luminosity functions

V/Vmax test of evolution

Morphological evolution

Passive stellar evolution

Number counts The global history of star-formation

Global History of Star-formation

The hot topic in observational cosmologyover the last few years


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over the last few years

Galaxies evolve

Galaxies produce stars Stars produce elements

These elements are essential for us

The global history of SF is the history of theproduction of elements and our history

Evolution of Light From aCollection of Stars Born in a

Single Burst

s


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Wavelength / nm

Lum

inosityperu

nitmass

Ultra Violet Optical

Live Fast Die Young Massive stars are short lived

Massive stars are very bright in UV

Number born similar to the number that die (c.F.


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(Newspapers & books)

Death of massive stars produces super novae

Death of massive stars produces elements Star birth rate proportional to UV luminosity

Star birth rate proportional to death rate (SN rate)

Star birth rate proportional to element production

Global History of Star Formation


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( ) ( )ttdNtdN D-= BornstarsBO,DeathstarsBO,

m

N(m) Initial

Mass-function

*BornstarBornstarsBO, & dNdN via IMF

Global History of Star FormationGlobal Star-formation rate is star formation rate per

unit volume


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( )

L

dLLL

dVUV

* fr

c&

HII Regions


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The trapezium regionwithin the Orion Nebula

Molecular Clouds

Reflection nebula within Orion


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A Local Star Forming Region in

Our Galaxy

The Trifid Nebula


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Cernicharo et al.

Interactions Between

Different Components


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Star Formation

IR

Dust

UV

IR

G


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H

Dust

UV

IR

IR

Gas

Gas

SN

e-e-

e-e-

Radio

DustUV


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M33 in H, OIII, 555nm

M82 a Star Forming Galaxy


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Wavelength /m

logLum

inosity

10 1001

Efstathiou et al. MNRAS

submitted

Star Formation Rate Measures

SFR = -1 CuvLuv


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SFR = -1 CHLH

SFR = C1.4GHz

L1.4GHz

SFR = (1-)-1CFIRLFIRCuv = 4.2 kg s

-1 / WHz-1

CH = 4.2X10-12 kg s-1 / W

C1.4GHz = 15.75

kg s

-1 / WHz-1

CFIR =0.12 kg s-1 / WHz-1

Comparison of

Star Formation

Rate Measures

SF

Rinfrare

d


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Star formation rates in the radio

Solar masses per yearCram et al 1999

SFRUV

SFRH

Summary

Star formation activity dominated by short-lived massive stars


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lived massive stars

Their UV light absorbed by dust and re-

emitted in FIR High z objects observed in sub-mm

Surveys in FIR and sub-mm required totrace obscured SFR history

Current Star

Formation Rate

FR/kg

s-1m-3

]


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IR

Radio Oliver, Gruppioni & Serjeant 1999 MNRAS Submitted

Serjeant, Gruppio

3191214 Distant Universe Lecture

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