A Measurement of CO(3-2) Line Emission from eBOSS Galaxies at $z\sim 0.5$ using Planck Data

TL;DR

This paper reports the first measurement of average CO(3-2) line emission at redshift 0.5 by correlating eBOSS galaxy data with Planck's CO(2-1) map, showing stacking methods are effective with current datasets.

Contribution

It introduces a novel approach to constrain molecular line emission using existing CMB and galaxy survey data, demonstrating the viability of stacking methods for line intensity mapping.

Findings

First measurement of CO(3-2) intensity at z~0.5

Stacking methods are effective with current data

Complementary to traditional LIM experiments

Abstract

Line intensity mapping (LIM) is a novel observational technique in astrophysics that utilizes the integrated emission from multiple atomic and molecular transition lines from galaxies to probe the complex physics of galaxy formation and evolution, as well as the large-scale structure of the universe. Modeling multiple line luminosities of galaxies with varying masses or their host halo masses poses significant uncertainty due to the lack of observational data across a wide redshift range and the intricate nature of astrophysical processes, making them challenging to model analytically or in simulations. While future experiments aim to measure multiple line intensities up to $z\sim 8$ across a wide volume using tomographic methods, we leverage publicly available datasets from the CMB experiment Planck and the galaxy survey eBOSS to constrain the CO(3-2) emission from galaxies. We correlate galaxies from eBOSS data onto the full-sky CO(2-1) map produced by Planck and report the first measurement of the average CO(3-2) intensity, $I_{CO} = 45.7 \pm 14.2\, \mathrm{Jy/sr}$ at $z\sim 0.5$ with $3.2\sigma$ confidence. Our findings demonstrate that stacking methods are already viable with existing observations from CMB experiments and galaxy surveys, and are complementary to traditional LIM experiments.