# Relationship between redshift and temperature

### What is the redshift of the Cosmic Microwave Background (CMB)? | thecuriousastronomer

Hence the microwave background appears now to have a temperature of K, but it was emitted from material at a redshift of , so when it. Abstract. The radiation temperature-redshift relation for Friedmann-Robertson- Walker where ΔE is the energy difference between the fine-structure levels, k is . For scenarios with late photon production, tests of the temperature-redshift relation (TRR) should therefore be reinterpreted as weak spectral.

Doppler widths of absorbers bd vs. Point-density contours are overplotted to guide the eye in the bottom panel. Standard image High-resolution image Export PowerPoint slide 3. Outlier Rejection Before fitting to the "ridge-line" of bmin versus NH i, we exclude those absorbers that have large errors in their measured parameters.

### cosmology - Redshift 1+z - CMB Temperature lower? - Physics Stack Exchange

These line widths correspond to the allowed line-width limits input to VPFIT and as such are artificial. The absorbers which remain after those exclusions are shown in Figure 1. Considering Figure 1we note a small set of points at very low bd which seem to lie significantly below the main locus of points. The data are sorted by their NH i.

The absorbers are placed into NH i bins of width 0. This process is iterated; the set of absorbers excluded via this method with bd lower than the mean are surrounded by blue boxes in Figure 2 and are excluded from the fitting procedure. The curves show the resulting best power-law fits determined by applying the bootstrap resampling method to the sample followed by the iterative power-law fit method described by Schaye et al.

Top center and right panels: Note that the bmin—NH i relation is roughly constant, but the expected NH i,0 evolution would require evolution in b0 and T0. Standard image High-resolution image Export PowerPoint slide In the following section, we proceed with the measurement of the bmin—NH i relation. Fitting bmin versus NH i In this section, we measure the bmin—NH i relation using the two data sets resulting from the outlier rejection methods described above.

Indirect measurement of T z is one of the most powerful cosmological tests available because it may exclude even the presence of a cosmological constant.

Unlike recent claims, we argue that the temperature at high z may be smaller than the standard prediction, thereby opening a window to alternative big bang models. However, this result by itself does not constitute a proof of the cosmological nature of the CMBR.

### Redshift - Wikipedia

If the universe really started from a homogeneous and isotropic collapsed state, the simplest prediction of such a model is that the temperature of this blackbody radiation has always been spatially uniform and higher in the past. How does the CMBR temperature increase when we look back in time?

The answer to this question is immediate only for Friedmann-Robertson-Walker FRW models where the radiation fluid expands adiabatically, especially after decoupling. However, in a more general framework, the function T z depends on the ingredients present in the FRW geometry or, equivalently, on the possible mechanisms acting upon the radiative component. If photon creation takes place, for instance, because of a continuous decaying vacuum energy density or some alternative mechanism of quantum gravitational origin, the standard linear law is necessarily modified.

In this case, measurements of the temperature at high redshifts constrain the free parameters of these models. As we shall see, the T z relation is a potential candidate for a new source of difficulties for the standard model.

## Astrophysics > Cosmology and Nongalactic Astrophysics

Temperature-redshift relation In order to emphasize the main assumptions involved in this problem, we first discuss how the temperature law T z may be derived in a framework more general than the familiar photon conserved picture. For the sake of generality, we assume that the material medium of the universe is a mixture of three different components: It is worth notice that the Cx term may describe several situations of current cosmological interest.

The most important cases are the following.

Although quite different on thermodynamical grounds, this approach resembles the old bulk viscosity description for matter creation. For this kind of models there is no second fluid component, because only an additional negative pressure takes place in the medium. In principle, we consider here a more general framework.