Abstract
In the context of next-generation spectroscopic galaxy surveys, new statistics of the distribution of matter are currently being developed. Among these, we investigated the angular redshift fluctuations (ARF), which probe the information contained in the projected redshift distribution of galaxies. Relying on the Fisher formalism, we show how ARF will provide complementary cosmological information compared to traditional angular galaxy clustering. We tested both the standard ΛCDM model and the wCDM extension. We find that the cosmological and galaxy bias parameters express different degeneracies when inferred from ARF or from angular galaxy clustering. As such, combining both observables breaks these degeneracies and greatly decreases the marginalised uncertainties by a factor of at least two on most parameters for the ΛCDM and wCDM models. We find that the ARF combined with angular galaxy clustering provide a great way to probe dark energy by increasing the figure of merit of the w0 − wa parameter set by a factor of more than ten compared to angular galaxy clustering alone. Finally, we compared ARF to the CMB lensing constraints on the galaxy bias parameters. We show that a joint analysis of ARF and angular galaxy clustering improves constraints by ∼40% on galaxy bias compared to a joint analysis of angular galaxy clustering and CMB lensing.
Highlights
In the coming years, large-scale optical and infrared (IR) surveys will map our Universe from the present epoch up to when it was roughly one tenth of its current age with unprecedented accuracy
Results for the ΛCDM model The results for the ΛCDM model are summarised in Fig. 5, where we show the ratio of the 1σ marginalised uncertainties when including angular redshift fluctuations (ARF) compared to using only angular galaxy clustering, for a DESI-like and a Euclid-like surveys
We show that the ARF are a promising cosmological observable for generation spectroscopic surveys
Summary
Large-scale optical and infrared (IR) surveys will map our Universe from the present epoch up to when it was roughly one tenth of its current age with unprecedented accuracy. While mining the faint Universe, these types of surveys will be sensitive, from a cosmological perspective, to the angular clustering of luminous matter, the cosmological aspects of gravitational lensing throughout cosmic epochs, the satellite population in halos, and the formation and evolution of the population of galaxy clusters. In this context, the Dark Energy Survey (DES, Abbott et al 2018) is currently providing state-of-the-art cosmological constraints in the late universe, and these should be further complemented by the Vera C. Rubin Observatory (LSST, Ivezicet al. 2019), which, at the same time, will explore the variability of the night sky in a regime of depth and time domain that remains practically unexplored to date
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