3k background radiation by roman werpachowski and peter holrick

3K background radiation3K background radiation

byby

Roman WerpachowskiRoman Werpachowski

andand

Peter HolrickPeter Holrick

StructureStructure

Overview and BackgroundAim and how to reach it COBE

– Technical Information– Interpretation of maps– Maps

Other projects in the future

What we will look at?What we will look at?

Source: Rod Nave, HyperPhysics, http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

What is detected?What is detected?Microwave Background Radiation (MBR):

wavelength=mm to cmIn terms of photons, or packets of light,

there are quite a few of them in the microwave background -- about 400 per cubic centimeter.

Travelling at the speed of light Our eyes can‘t see itTV waves are similar to 3k radiation => on

terrestic TVs few percent of the snow is CMB (Cosmic microwave background)

Source: Wayne Hu, An Introduction to the Cosmic Microwave Background, http://background.uchicago.edu/~whu/beginners/introduction.html

What do we see?What do we see?

By looking in the sky, we actually look backwards in time

Light from more distant objects takes longer to reach us

We can see back a few billion years

MBR is from an 300 000 year old universe:

Soup of fundamental particles like electrons, protons, helium nuclei, neutrinos


Why 2,73° K?Why 2,73° K?Because of the expansion, the microwave

background is very cold now - 3 degrees above absolute zero.

It's wavelength has been stretched out of the visible and into the microwave regime of millimeters to centimeters.

Temperature is almost constant.

Source: Wayne Hu, An Introduction to the Cosmic Microwave Background, http://background.uchicago.edu/~whu/beginners/introduction.html Rod Nave, HyperPhysics, http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Temperature anisotropiesTemperature anisotropies

Small variations in the temperature of the background radiation from point to point on the sky are called anisotropies.

These anisotropies were first detected for the whole sky by the COBE satellite in 1989.

They produced a map of the sky:

Source:Source: Wayne Hu, An Introduction to the Cosmic Microwave Background, http://background.uchicago.edu/~whu/beginners/introduction.html

colors represent temp-erature on the sky

StructureStructure




Aim: Aim:

To understand how the universe went from a smooth particle soup to a complex system of galaxies

Using the surface of the soup in the microwave back-ground to help understand and solve this question


The data analysis piplineThe data analysis pipline

Source:Source: Max Tegmark, CMB data analysis center, http://www.hep.upenn.edu/~max/cmb/pipeline.html

Parameterestimates

Sky

Measurement

Raw data

Cleaning

Mapmaking

Time-ordereddata

Multi-Frequencymaps

Foregroundremoval

Sky map

Powerestimation

Power spectrum

ModelTesting

Why power spectrum estimation?Why power spectrum estimation?

If the statistical properties of the CMB fluctuations are isotropic and Gaussian (which they are in the standard inflationary models), then all the cosmological information in a sky map is contained in its power spectrum

This means that all the information from even a giant data set (say a map with n=10^7 pixels) can be reduced to just a couple of thousand numbers, greatly facilitating parameter estimation

It allows a model-independent comparison between different experiments

one-to-one correspondence between visible features in the power spectrum and the physical processes one is studying

Source: Max Tegmark, CMB data analysis center, http://www.hep.upenn.edu/~max/cmb/pipeline.html

Angular power spectrum of Angular power spectrum of CMB anisotropiesCMB anisotropies

Source:Source: Max Tegmark, CMB data analysis center, http://www.hep.upenn.edu/~max/cmb/experiments.html

Experiments:• Satellites

• COBE • MAP • Planck (COBRAS/SAMBA)

• Balloon-born• FIRS, ARGO, MAX, MSAM,

BAM, QMAP (Princeton, Penn, QMASK data), BOOMERanG, MAXIMA, Top Hat, HACME, ACE, Archeops, BEAST

• Ground-based• Tenerife,

South Pole,Saskatoon,Python,and many more (>20) multipole space

StructureStructure




COBE - Cosmic Background ExplorerCOBE - Cosmic Background Explorer

The COBE satellite was developed by NASA's Goddard Space Flight Center to measure the diffuse infrared and microwave radiation from the early universe to the limits set by our astrophysical environment.

launched November 18, 1989 3 instruments:

– Far Infrared Absolute Spectrophotometer (FIRAS) to compare the spectrum of the cosmic microwave background radiation with a precise blackbody,

– Differential Microwave Radiometer (DMR) to map the cosmic radiation sensitively, and

– Diffuse Infrared Background Experiment (DIRBE) to search for the cosmic infrared background radiation.

Source: The COBE Home Page, http://space.gsfc.nasa.gov/astro/cobe/

The COBE datasets were developed by the NASA Goddard Space Flight Center under the guidance of the COBE Science Working Group and were provided by the NSSDC.

COBE - Cosmic Background ExplorerCOBE - Cosmic Background Explorer

FIRAS: PrincipleFIRAS: Principle

Far Infrared Absolute Spectrophotometer (FIRAS)

Should measure precisely the spectrum of the cosmic microwave background radiation over the wavelength range from 0.1 to 10 mm

7 degree field of view polarizing Michelson interferometer with bolometer detectors to determine the

intensity of the incoming light at a large number of wavelengths (i.e., a spectrum) simultaneously.

Cosmological discovery: FIRASCosmological discovery: FIRAS The cosmic microwave background (CMB) spectrum is

that of a nearly perfect blackbody with a temperature of 2.725 +/- 0.002 K.

This observation matches the predictions of the hot Big Bang theory extraordinarily well

It indicates that nearly all of the radiant energy of the Universe was released within the first year after the Big Bang.

Far Infrared Absolute Spectrophotometer (FIRAS)

Should detect anisotropy 2 antenna for each wavelengt: 3.3, 5.7 and 9.6mm Antennas are 60 degrees apart Antenna are switched to ensure difference comes

from the sky and not from differences in the antennas

7 degree field of view

DMRDMR

Differential Microwave Radiometer (DMR)

Cosmological discovery: DMRCosmological discovery: DMR The CMB was found to have intrinsic "anisotropy" for

the first time, at a level of a part in 100,000. These tiny variations in the intensity of the CMB over the

sky show how matter and energy was distributed when the Universe was still very young.

Later, through a process still poorly understood, the early structures seen by DMR developed into galaxies, galaxy clusters, and the large scale structure that we see in the Universe today.


DIRBEDIRBE

Diffuse Infrared Background Experiment (DIRBE)

Should minimize response to objects outside the desire 0.7 degrees view

Internal temperature comparison Ten wavelengths (1.25 to 240μm) Polarisation at three shortest

wavelengths

Cosmological discovery: Cosmological discovery: DIRBEDIRBE Infrared absolute sky brightness maps in the wavelength

range 1.25 to 240 microns were obtained to carry out a search for the cosmic infrared background (CIB).

The CIB was originally detected in the two longest DIRBE wavelength bands, 140 and 240 microns, and in the short-wavelength end of the FIRAS spectrum.

Subsequent analyses have yielded detections of the CIB in the near-infrared DIRBE sky maps.

The CIB represents a "core sample" of the Universe; it contains the cumulative emissions of stars and galaxies dating back to the epoch when these objects first began to form.

Diffuse Infrared Background Experiment (DIRBE)

Interpretation of COBE-mapsInterpretation of COBE-maps

Theoretical map, if COBE looked down2 dimensional representation of the 3

dimensional surface of the earth



COBE has rather blurry vision and can only see large features corresponding to 7 degree separations on the sky


Result:


COBE also has noise in its detectors like you would have with bad reception on your TV


Result:


To get rid of the noise, maps can be smoothed. This brings out the large features like continents but fine details are lost in the map


Result:


Similarly COBE's map of the background radiation only shows you the large features in the sky and all finer details are lost.


Example mapsExample maps

Maps based on observations made with the DMR over the entire 4-year mission, at each of the three measured frequencies, following dipole subtraction.

the red and blue spots correspond to regions of greater or lesser density in the early universe.


Example mapsExample maps Maps based on 53 GHz (5.7 mm

wavelength) observations made with the DMR over the entire 4 year mission (top) on a scale from 0 - 4 K,

showing the near-uniformity of the CMB brightness, (middle) on a scale intended to enhance the contrast, and

(bottom) following subtraction of the dipole component.

Emission from the Milky Way Galaxy is evident in the bottom image.


This image combines data from the DIRBE obtained at infrared wavelengths of 25, 60 and 100 µm. The sky brightness at these wavelengths is represented respectively by blue, green, and red colors in

the image. The image is dominated by the thermal emission from interstellar dust in the Milky Way.

Large and Small Magellanic Clouds

Orion molecular clouds, which are active "stellar nurseries" in our Galaxy

structured, warmer emission from interplanetary dust


This image combines data from the DIRBE obtained at infrared wavelengths of 100, 140 and 240 µm. The sky brightness at these wavelengths is represented respectively by blue, green, and red colors in

the image. The image is dominated by the thermal emission from interstellar dust in the Milky Way.

Large and Small Magellanic Clouds

Orion molecular clouds, which are active "stellar nurseries" in our Galaxy

structured, warmer emission from interplanetary dust

StructureStructure




Microwave Anisotropy ProbeMicrowave Anisotropy Probe The Microwave Anisotropy Probe (MAP) will make a

map of the temperature fluctuations of the CMB radiation with much higher resolution, sensitivity, and accuracy than COBE.

MAP is the first mission to use an L2 orbit as its permanent observing station. L2 is a semi-stable region of gravity that is about 4 times further than the Moon, following the Earth around the Sun.

June 30, 2001: MAP Launch Oct. 1, 2001: MAP Arrives at L2 One full sky scan last 6 months Jan. 2003: First Data Release

Source: http://map.gsfc.nasa.gov/m_mm/ms_status.html

Microwave Anisotropy ProbeMicrowave Anisotropy Probe

Source: http://map.gsfc.nasa.gov/m_mm/ms_status.html

PLANCKPLANCK

Source:Source: http://astro.estec.esa.nl/SA-general/Projects/Planck/

To be launched in the first quarter of 2007

By European Space Agency

Better and more instruments

L2 orbit

Aim: Aim:

To understand how the universe went from a smooth particle soup to a complex system of galaxies

Using the surface of the soup in the microwave back-ground to help understand and solve this question


Degree Angular Scale Degree Angular Scale Interferometer (DASI) Interferometer (DASI) Polarization of CMB supports current models of

the universe

3k background radiation by roman werpachowski and peter holrick

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