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Cosmology 2004 – 2005 Part I. Prof. Guido Chincarini

Cosmology 2004 – 2005 Part I

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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.

Cosmologia A.Year 04_05- Milano Bicocca

- 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.

Cosmologia A.Year 04_05- Milano Bicocca

- Coordinates: guido@merate.mi.astro.it - 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.

Cosmologia A.Year 04_05- Milano Bicocca

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:

- 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:

- 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:

- 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.

Cosmologia A.Year 04_05- Milano Bicocca

I’m astounded by people who want to “know” the Universe

when it’s hard enough to find your way around Chinatown. (Woody Allen)

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

- 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)

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

Le Tappe Finali

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

Cosmologia A.Year 04_05- Milano Bicocca

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.

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

- 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?

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

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.

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

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The Hubble Diagram

in the low red-shift limit(V=HoxD)

Hubble&

Humason

1931

Cosmologia A.Year 04_05- Milano Bicocca

530 km/s Mpc

Cosmologia A.Year 04_05- Milano Bicocca

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:

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

GRBs ??

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

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.

Cosmologia A.Year 04_05- Milano Bicocca

Redshifts

LaForest

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

See Black Body Radiation

Cosmologia A.Year 04_05- Milano Bicocca

Cosmologia A.Year 04_05- Milano Bicocca

Da: Materia Oscura ed Energia Oscura

Guido Chincarini

Cosmologia A.Year 04_05- Milano Bicocca