Cosmology With Quasars: Predictions for eROSITA From a Quasar Hubble Diagram

Elisabeta Lusso

doi:10.3389/fspas.2020.00008

Abstract

The effort for understanding the matter and energy content of the Universe and its evolution relies on different probes, such as cosmic background radiation, cluster lensing, supernovae. Yet, we are still far from grasping what dark matter is made of, and what the physical origin of dark energy is. Our group has developed a technique that makes use of the observed non-linear relation between the ultraviolet and the X-ray luminosity in quasars to provide an independent measurement of their distances, thus turning quasars into standardizable candles. This technique, at present, it is mostly based upon quasar samples with data from public catalogues both in the X-rays and in the optical/ultraviolet and extends the Hubble diagram of supernovae to a redshift range still poorly explored (z>2). From the X-ray perspective, we are now on the eve of a major change, as the upcoming mission eROSITA is going to provide us with up to ~millions of active galactic nuclei across the entire sky. Here we present predictions for constraining cosmological parameters such as the amount of dark matter (Omega_M), dark energy (Omega_L) and the evolution of the equation of state of dark energy (w) through the Hubble diagram of quasars, based on the 4-year eROSITA all-sky survey. Our simulations show that the eROSITA quasars, complemented by redshift and broad-band photometric information, will supply the largest quasar sample at z3.

Highlights

The driving forces behind the present era of precision cosmology have been the detection of anisotropies in the cosmic microwave background (CMB; e.g., Smoot et al, 1992) and the discovery of the accelerated expansion of the Universe, based on the Hubble diagram of Type Ia supernovae (SNe Ia), the standard candles par excellenceThe eROSITA Quasar Hubble Diagram: A Forecast (e.g., Riess et al, 1998; Perlmutter et al, 1999)
Uncertainties on F2500 are computed by propagating the magnitude uncertainties from the spectral energy distributions (SEDs) we compiled for each SDSS quasar in the catalog
The current accuracy on from supernovae Ia is ∼8%, whilst the precision on from the simulated quasar Hubble diagram is on the order of ∼30%

Summary

INTRODUCTION

The driving forces behind the present era of precision cosmology have been the detection of anisotropies in the cosmic microwave background (CMB; e.g., Smoot et al, 1992) and the discovery of the accelerated expansion of the Universe, based on the Hubble diagram (i.e., the distance modulus vs. redshift relation) of Type Ia supernovae (SNe Ia), the standard candles par excellence. At the time of writing, the most extended spectroscopic coverage in the optical/UV is provided by the Sloan Digital Sky Survey (Pâris et al, 2018), which supplies more than ∼500,000 quasars with spectroscopic redshift up to z ∼ 7. This sample needs to be cross-matched with the current X-ray catalogs, namely the Chandra CXC2.01 (Evans et al, 2010) and the 3XMM Data Release 82 (Rosen et al, 2016), which contain all the X-ray sources detected by the XMM-Newton and Chandra observatories that are publicly available in the archives. In this work we discuss the potential of the 4-years eROSITA all-sky survey for constraining cosmological parameters, such as m, and w, through the Hubble diagram of quasars

THE SIMULATED EROSITA QUASAR

RESULTS

DISCUSSION

On the Tension of the Hubble