Unveiling the Universe with emerging cosmological probes

Abstract

The detection of the accelerated expansion of the Universe has been one of the major breakthroughs in modern cosmology. Several cosmological probes (Cosmic Microwave Background, Supernovae Type Ia, Baryon Acoustic Oscillations) have been studied in depth to better understand the nature of the mechanism driving this acceleration, and they are being currently pushed to their limits, obtaining remarkable constraints that allowed us to shape the standard cosmological model. In parallel to that, however, the percent precision achieved has recently revealed apparent tensions between measurements obtained from different methods. These are either indicating some unaccounted systematic effects, or are pointing toward new physics. Following the development of CMB, SNe, and BAO cosmology, it is critical to extend our selection of cosmological probes. Novel probes can be exploited to validate results, control or mitigate systematic effects, and, most importantly, to increase the accuracy and robustness of our results. This review is meant to provide a state-of-art benchmark of the latest advances in emerging “beyond-standard” cosmological probes. We present how several different methods can become a key resource for observational cosmology. In particular, we review cosmic chronometers, quasars, gamma-ray bursts, standard sirens, lensing time-delay with galaxies and clusters, cosmic voids, neutral hydrogen intensity mapping, surface brightness fluctuations, stellar ages of the oldest objects, secular redshift drift, and clustering of standard candles. The review describes the method, systematics, and results of each probe in a homogeneous way, giving the reader a clear picture of the available innovative methods that have been introduced in recent years and how to apply them. The review also discusses the potential synergies and complementarities between the various probes, exploring how they will contribute to the future of modern cosmology.

Cosmic chronometers to calibrate the ladders and measure the curvature of the Universe. A model-independent study

“…Thus, an improvement in the CCH data, either in terms of quality or quantity, can also have a non-negligible impact on the outcome of this method. Euclid, for instance, is expected to provide up to a few thousands passively evolving galaxies at z 2, increasing by 2 orders of magnitude the currently available statistics (Moresco et al 2022).…”

New Observational H(z) Data from Full-spectrum Fitting of Cosmic Chronometers in the LEGA-C Survey

“…But the other option is also acceptable, and we get compatible H(z) measurements for them during the following step analyses. We decide to use as a baseline the set of parameters that better reproduces the Ca II H/K feature (the last row of Table 1, since it has been proven to be a very powerful and important diagnostic to trace the purity of CC samples; see Moresco et al 2018;Borghi et al 2022a;Moresco et al 2022), and having a significantly different H/K in the reconstructed spectrum would mean notcorrectly reproducing the behavior of our data, possibly resulting in biases in the results. Moreover, we notice that all of the models present a compatible 2 c n , but this model also has the advantage of avoiding additional calibration, since the LEGA-C DR2 spectra are flux calibrated using UltraVISTA's photometric data.…”

“…At the moment, there are suggested theories to try to explain it, even if they are not definitive (Di Valentino et al 2021). Alternative cosmological probes (Moresco et al 2022) can play an important role in obtaining additional independent, high-precision measurements to assess the current Hubble tension's reliability. It also becomes evident that a single probe is not adequate to constrain the properties and evolution of the universe accurately and completely.…”

Testing time-delayed cosmology

“…The Hubble data are taken from the compilation in Ref. [45] another observable f σ 8 (z), where z is the redshift, that are both dependent on the amplitude of perturbations. The former quantity is the speed of growth of perturbations in the Universe with respect to the cosmic expansion, and the latter is essentially the growth rate scaled by the evolving root-meansquare of matter perturbations.…”

“…We consider the Hubble expansion rate data compiled in Table 1 of Ref. [45] as well as the growth rate and f σ 8 (z) data compiled in Tables 1 and 2 of Ref. [57], respectively.…”