Probing cosmic velocity-density correlations with galaxy luminosity modulations

TL;DR

This paper proposes using luminosity-density correlations in galaxy surveys to measure cosmic velocity-density signals, offering a new cosmological probe with high precision on large scales.

Contribution

It introduces a method to extract velocity-density correlations from luminosity modulations in galaxy surveys, neglecting lensing effects at certain redshifts.

Findings

Velocity-density correlation can be measured with high signal-to-noise ratio (>10) on scales 10-100 Mpc.

Luminosity-density monopole provides insights into galaxy formation and environmental effects.

Method applicable to SDSS-like surveys at redshift 0.1.

Abstract

We study the possibility of using correlations between spatial modulations in the observed luminosity distribution of galaxies and the underlying density field as a cosmological probe. Considering redshift ranges, where magnification effects due to gravitational lensing may be neglected, we argue that the dipole part of such luminosity-density correlations traces the corresponding velocity-density signal which may thus be measured from a given galaxy redshift catalogue. Assuming an SDSS-like survey with mean density $\overline{n}$ = 0.01 ($h^{-1}$ Mpc)$^{-3}$ and effective volume $V_{\rm eff}$ = 0.2 ($h^{-1}$ Gpc)$^{3}$ at a fiducial redshift z = 0.1, we estimate that the velocity-density correlation function can be constrained with high signal-to-noise ratio $\gtrsim$ 10 on scales 10-100 Mpc. Similar conclusions apply to the monopole which is sensitive to the environmental dependence of galaxy luminosities and relevant to models of galaxy formation.