On the WMAP image of the cosmic microwave background radiation, are the higher density irregularities the brighter bits or the darker bits?
The colour code shows fluctuations of CMBR temperature about its mean value of
The averaged CMBR temperature is
Given below is a map of temperature fluctuations about this average value, created from the 9 year data of WMAP. In this map the temperature fluctuations about the average value are shown in a scale of
The pixels in red represent temperatures that are
The pixels in dark blue represent temperature that are
What do they mean?: Higher temperature indicates higher matter density.
Density Contrast Field: Fluctuations in mass density are quantified by the density contrast field
Temperature Contrast Field: Fluctuations in CMBR temperature are quantified by the temperature contrast field
There is direct relation connecting the two which can be deduced from the fundamental principles: