cosmology 2004 – 2005 part i

1 Cosmologia A.Year 04_05- Milano Bicocca

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Cosmology 2004 – 2005Part I

Prof. Guido Chincarini

The scope of these lectures is to give to the student a feeling for modern problems in cosmology, understand the basic concepts and give to him some tools to work with. Often I will deal with a rough approximation in deriving equations and numerical solutions. That is to facilitate the comprehension. The student can refer to advanced textbooks and articles to refine his/her computational capabilities.

The Introduction give a general overview of the state of the art referring to basic matters and problems which are being studied now days. I will then, before getting to the world models, revisit the Luminosity Function of galaxies in its more general meaning in order to give to the students a good grasp on this fundamental distribution function and ideas on where our knowledge could and/or need to be improved.


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Notes & References• I will still work on these lectures during the next semester,.

Indeed various parts need to be improved, other expanded and above all I must add an large number of references to help the students and also to acknowledge the contribution of others when needed and due.

• On the other hand I realize that many students and colleagues like to have them the way they are and eventually get the updates later on when ready. I understand that so that I decided to put them on the Web.

• I appreciate if they are quoted when used and if the students, or anyone for that matter, let me know about errors and typos.

• Also let me know ways to improve them.


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CosmologiaNotizie Pratiche

• Coordinates: [email protected] - Phone: 039 999 111 – • FAX 039 9991160• Lectures: Tuesday & Wednesday 8:30 – 10:30• Notes: The students will give a short (20 minutes lecture) at the end of

the semester.• Exams: Can be done with appointment any time the student wants. The

exam consists of a discussion on a topic selected by the student (generally the content of the lecture the student presented at the end of the semester) and on some of the arguments dealt during the regular lectures.

• Relax: Picnic at the Observatory in Merate hopefully will continue. Eventually we organize a joint gathering. Everybody is welcome.


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Shall we try?The literature and the web is very rich. Data and catalogues are available at any

wavelength (Radio, HST, XMM, Chandra etc) and tools to analyze them, as for instance ASDC, are also at hand. There are beautiful pictures as well.

The idea is: a. Could we try, as a group, to tackle or re-work a cosmological problem or b. Could we try to tackle many different and simpler problems with pairs or single

students orc. Better forget about

The Risks:A. We might fail because the problem (or problems) is not well chosenB. Since I am very busy I might not find the time to follow properly the students. I

might not be capable of carrying out on this first attempt what I have in mind.C. We discover it is a silly idea. I did not star to plan on it yet.

The Reason for this:I. Things in science and in life are changing and we have to find new ways not only

to organize ourselves but also to teach, become creative and find a way of thinking and operating with broader view.


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I’m astounded by people who want to “know” the Universe when it’s hard enough to find your way around Chinatown.

(Woody Allen)


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Composizione artistica della NASA


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The evolving UniverseMilestones

• Big Bang. (0.0)• Planck’s time (10-43 sec)• Nucleosynthesis - He - Gamow.

(~100 sec)• Time of Equivalence. (7000 -

10000 years)• Time of Recombination.

(~25000 years) - MWB• The formation of galaxies and

Large Scale Structures.(~500 Ml years)

• The present (~ 12 109 years)


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Il Ciclo della Materia

• Interstellar Medium• Stars• Giant Stars• Supernovae• Interstellar Medium • Stars• ……….


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•Brown dwarfs•White Dwarf•Neutron Stars•Black Holes•Big Squeeze or the Vacuum

Le Tappe Finali


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The simulated image shows what the accretion disk around a black hole might look like. The distortions of time and space by the intense gravity of the black hole and motion of the material at close to the speed of light cause emission to be shifted to longer and shorter wavelengths.


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Some of the Big Questions• The Cosmological constant• The Nature of Dark Matter• MWB – Fluctuations on small

scales• The formation and evolution of:

– Galaxies– Clusters of Galaxies – The Large Scale Structure– High z Galaxies & Starbursts

• Primordial Black Holes• The Gamma Ray Bursts

The Galactic Center (IR)

Expanding Universe

Cosmic Time

0 5 10 15 20 25 30

EX

P. P

aram

eter

0

5

10

15

20

25


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Cosmological Tests leading to qo

1. Hubble Diagram2. Galaxy counts-magnitude3. The angular diameters - z relation4. Age of the oldest objects5. Lensing6. Could we a priori imagine perturbation of the Hubble

flow?7. How far could we observe and still plot the Hubble

diagram?8. How do we know the standard candle do not change

with time? And what about the physical constants?


15

-20

0

20Length

-40

-20

0

20

40

Width

-200

2040

Height

-20

0

20Length


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-20

0

20Length

-40

-20

0

20

40

Width

-80-60-40-200

Height

-20

0

20Length


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The amount of matter/energy in the universe determines the rate at which the expansion of the universe is decelerated by the gravitational attraction of its contents, and thus its future state: whether it will expand forever or collapse into a future Big Crunch.


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The Hubble Diagram5log5 DMm in the low red-shift limit(V=HoxD)

MHczm o log525log5

Hubble&

Humason

1931


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530 km/s Mpc


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25)];;(log[5 KzDMm ML

The Hubble Diagram at high z

For an object of known absolute magnitude M, a measurement of the apparent magnitude m at a given z is sensitive to the universal parameters, through the luminosity distance:


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3

45

z =

Distance Clusters of Galaxies

High z Radio Galaxies

Peak of Quasars Counts

High z Galaxies

Most Distant Radio Galaxy

Most distant Quasar

Most Distant Galaxy

TIME

13 (1.)4.6 (.35)

2.5 (.19)1.6 (.12)

Tempo in Miliardi di anni & %

0.9 (.07)

z=6.28

GRBs ??


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M oriond 2002 21

T he IG M A bsorption (z=3 ,4 ,5 ,6)

3000 3500 4000 45000

0.2

0.4

0.6

0.8

1

4000 4500 5000 5500 60000

0.2

0.4

0.6

0.8

1

5000 5500 6000 6500 70000

0.1

0.2

0.3

0.4

0.5

5500 6000 6500 7000 7500 8000 85000

0.025

0.05

0.075

0.1

0.125

0.15


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z=2.5

z=8

z=12

HIIonized

H2 cooling

T ~ 11

T~ 14000 z~10

z=20


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Star Formation Rate

The distribution has been obtained by fitting the curve proposed by Lamb and Reichart and adding a Gaussian distribution in the range 15<z<21.

At low redshifts the results by Rowan & Robinson have been preferred and these match also better the simulations by Gnedin and Ostriker.

The peak at z~19 (or may be 18) corresponds to the formation of Pop. III stars due to cooling by molecular hydrogen.

0 5 10 15 20Redshift

-2.5

-2

-1.5

-1

-0.5

0

0.5

goL

RFS

,nusMryh

cpM

^3

Star Formation Rate


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RedshiftsEm Lines as a function of z

z0 2 4 6 8 10

in

A)

0

5000

10000

15000

20000

25000

30000

H

[OIII] 5007

H

[OII] 3727

MgII 2798

CIII] 1909CIV 1549

L 1216LForest


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How many photons do we get

19 19.5 20 20.5 21 21.5 220

200

400

600

800

• The Number of photons we receive as a function of the apparent magnitude:• Assume a 4 meters telescope and a 900 A wide filter.• Now let’s put a 40W light at the distance of the Moon (3.84 105 km)• We will get about 225 photons per second. More or less an object with mv=20.6

(we assumed 30% efficiency for the optics).• The new Moon night sky far from any city or human light pollution has mv=21.7

That is about 60 photons per second.


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Distant Galaxy with ISAAC


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See Black Body Radiation


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Materia Oscura

Ω < 0.1 Barionica > 0.1

Non Barionica

Clumped H2 Gas

Polvere MACHOs

VMO Nane Brune

Black Holes

Particelle esotiche ??

Non - Termiche

Equilibrio Termico

Assioni

??

Neutrini Leggeri (25 eV)

WIMPs

Da: Materia Oscura ed Energia Oscura

Guido Chincarini

cosmology 2004 – 2005 part i

Documents

single students orbetter

simpler problems

modern problems

regular lectures

milano bicoccashall

general overview

minutes lecture

general meaning