Fundamental Physics from Future Spectroscopic Surveys

A new method to determine H0 from cosmological energy-density measurements

8 May 2024, 08:50

10m

Auditorium (Building 50)

Session 9

Speaker

Alex Krolewski

Description

We introduce a new method for measuring the Hubble parameter from low-redshift large-scale observations that is independent of the comoving sound horizon. The method uses the baryon-to-photon ratio determined by the primordial deuterium abundance, together with Big Bang Nucleosynthesis (BBN) calculations and the present-day CMB temperature to determine the physical baryon density ${\mathrm{\Omega }}_b{h}^2$. The baryon fraction ${\mathrm{\Omega }}_b/{\mathrm{\Omega }}_m$ is measured using the relative amplitude of the baryonic signature in galaxy clustering, scaling the physical baryon density to the physical matter density. The physical density ${\mathrm{\Omega }}_m{h}^2$ is then compared with the geometrical density ${\mathrm{\Omega }}_m$ from Alcock-Paczynski measurements from Baryon Acoustic Oscillations (BAO) and voids, to give $H_0$. Current data is only weakly constraining and therefore consistent with both the distance-ladder and CMB $H_0$ determinations, but near-future large-scale structure surveys (such as the full DESI and Euclid surveys) will obtain 3--4$\times$ tighter constraints. Including type Ia supernovae and uncalibrated BAO, and using the baryon signature in BOSS galaxy clustering, we measure $H_0={67.1}_{-5.3}^{+6.3}$ km s${}^{-1}$ Mpc${}^{-1}$. We find similar results when varying analysis choices, such as measuring the baryon signature from the reconstructed correlation function, or excluding supernovae or voids.

Presentation materials

Future_Spectroscopic_Surveys.pdf