Is the Universe transparent?

Abstract

We present our study on cosmic opacity, which relates to changes in photon number as photons travel from the source to the observer. Cosmic opacity may be caused by absorption/scattering due to matter in the universe, or by extragalactic magnetic fields that can turn photons into unobserved particles (e.g. light axions, chameleons, gravitons, Kaluza-Klein modes), and it is crucial to correctly interpret astronomical photometric measurements like type Ia supernovae observations. On the other hand, the expansion rate at different epochs, i.e. the observational Hubble parameter data H(z), are obtained from differential ageing of passively evolving galaxies or from baryon acoustic oscillations and thus are not affected by cosmic opacity. In this work, we first construct opacity-free luminosity distances from H(z) determinations, taking correlations between different redshifts into consideration for our error analysis. Moreover, we let the light-curve fitting parameters, accounting for distance estimation in type Ia supernovae observations, free to ensure that our analysis is authentically cosmological-model-independent and gives a robust result. Any non-zero residuals between these two kinds of luminosity distances can be deemed as an indication of the existence of cosmic opacity. While a transparent universe is currently consistent with the data, our results show that strong constraints on opacity (and consequently on physical mechanisms that could cause it) can be obtained in a cosmological-model-independent fashion.PACS numbers: 98.80.-k, 98.80.Es

Cosmic opacity: Cosmological-model-independent tests from gravitational waves and Type Ia Supernova

“…The results, in the framework of three model-independent methods (nearby SNe Ia method, interpolation method and smoothing method), converged to a point that the effects of cosmic opacity are vanished. Such methodology was recently extended by Liao et al [25], who examined the residuals between the constructed opacity-free luminosity distances from H(z) determinations and distance estimation in type Ia supernovae observations with variable light-curve fitting parameters. A transparent universe is currently consistent with the current EM data.…”

“…More recently, some substantial progress has been made in the measurements of the Hubble parameter H(z), which are combined with different sub-samples of SNe Ia observations to quantify the cosmic opacity [23,24]. However, it is worth noting that H(z) describes the expansion rate of the universe rather than the distance, i.e., the angular diameter distance obtained by integrating these scattered points will inevitably lead to large uncertainties, which indicated the importance of taking the correlations between different redshifts into account [25]. More importantly, considering the limited sample size of H(z) measurements, one has also to take care of the errors due to the mismatch between the H(z) redshift and the closest SNe Ia in the companion SNe Ia sample adopted.…”

Constraining axionlike particles using the distance-duality relation

“…Holanda et al [85] parametrized the redshift dependence of η(z) in two distinct forms, η(z) = 1 + η 0 z(P1) and η(z) = 1 + η 0 z/(1 + z)(P2) and investigated the η 0 parameter by employing the luminosity distance D L measurements from Type Ia supernovae (SNe Ia) and diameter distance D A from galaxy clusters [86,87]. Several other authors have also tested the DDR relation using different observations: SNe Ia plus cosmic microwave background (CMB) and barion acoustic oscillations (BAO) [88], SNe Ia plus H(z) data [77,[89][90][91], gas mass fraction of galaxy clusters and SNe Ia [92,93], CMB spectrum [94], gammaray burst (GRB) plus H(z) [95], SNe Ia plus BAO [96], gas mass fraction plus H(z) [97], gravitational lensing plus SNe Ia [98], SNe Ia and radio galaxy plus CMB [99]. Most of the above authors obtain no significant deviation in DDR relation, although, roughly the scatter in η 0 parameter is observed as ±0.1 to ±0.…”

Probing the cosmic opacity from future gravitational wave standard sirens

“…Clusters × Union2.1 (B) [44] 0.009± 0.059 0.055 0.014± 0.071 0.069 H(z) × Union2.1(B) [42] −0.01 ± 0.10 −0.01 ± 0.12 H(z)× JLA (B) [43] 0.07± 0.107 0.121 ages of old objects × Union2.1 (B) [40] 0.016± 0.078…”