cosmo04_Int_Part_1

Cosmology 2004 – 2005
Part 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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Cosmologia
Notizie Pratiche
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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.
b.
c.
Could we try, as a group, to tackle or re-work a cosmological problem or
Could we try to tackle many different and simpler problems with pairs or single
students or
Better forget about
The Risks:
A.
B.
C.
We might fail because the problem (or problems) is not well chosen
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.
We discover it is a silly idea. I did not star to plan on it yet.
The Reason for this:
I.
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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 Universe
Milestones
• 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
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Interstellar Medium
Stars
Giant Stars
Supernovae
Interstellar Medium
Stars
……….
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Le Tappe Finali
•Brown dwarfs
•White Dwarf
•Neutron Stars
•Black Holes
•Big Squeeze or the
Vacuum
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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
Expanding Universe
– Galaxies
– Clusters of Galaxies
– The Large Scale Structure
– High z Galaxies & Starbursts
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EXP. Parameter
• The Cosmological constant
• The Nature of Dark Matter
• MWB – Fluctuations on small
scales
• The formation and evolution of:
15
10
5
0
0
5
10
15
20
25
30
Cosmic Time
The Galactic Center (IR)
• Primordial Black Holes
• The Gamma Ray Bursts
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Cosmological Tests leading to qo
1.
2.
3.
4.
5.
6.
7.
8.
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Hubble Diagram
Galaxy counts-magnitude
The angular diameters - z relation
Age of the oldest objects
Lensing
Could we a priori imagine perturbation of the Hubble
flow?
How far could we observe and still plot the Hubble
diagram?
How do we know the standard candle do not change
with time? And what about the physical constants?
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Height 20
0
-20
40
20
0
-20
-20
0
Length
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Width
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15
0
-20
Height -40
-60
-80
40
20
0
-20
-20
0
Length
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Width
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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 Diagram
m  M  5 log D  5 in the low red-shift limit(V=HoxD)
m  5 log cz  25  5 log Ho  M
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Hubble&
Humason
1931
ii
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530 km/s Mpc
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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:
m  M  5 log[ DL( z; M ;  )]  K  25
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GRBs ??
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The IGM Absorption (z=3,4,5,6)
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1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
3000
3500
4000
4500
4000
0.5
4500
5000
5500
6000
0.15
0.125
0.4
0.1
0.3
0.075
0.2
0.05
0.1
0.025
0
5500
0
5000
5500
6000
6500
6000
6500
Moriond 2002
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7000
7500
8000
8500
7000
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Star Formation Rate
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.
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Star Formation Rate
Log SFR,Msun yr h Mpc^3
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.
0.5
0
-0.5
-1
-1.5
-2
-2.5
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Redshift
15
20
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Redshifts
Em Lines as a function of z
30000
[OIII] 5007
25000
H
MgII 2798
H
20000
in A)
[OII] 3727
CIII] 1909
15000
CIV 1549
10000
L 1216
L Forest
5000
0
0
2
4
6
8
10
z
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How many photons do we get
800
600
400
200
0
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19.5
20
20.5
21
21.5
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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 10 5 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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Da:
Materia Oscura ed Energia Oscura
Guido Chincarini
Materia Oscura
> 0.1
Non Barionica
Ω < 0.1 Barionica
Clumped H2
Gas
Polvere
MACHOs
VMO
Nane Brune
Particelle esotiche
??
Non - Termiche
Assioni
??
Black Holes
Equilibrio Termico
Neutrini Leggeri (25 eV)
WIMPs
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