Extragalactic CO emission lines in the CMB experiments: a forgotten signal and a foreground

Abstract

High resolution cosmic microwave background (CMB) experiments have allowed us to precisely measure the CMB temperature power spectrum down to very small scales (multipole $\ell \sim 3000$). Such measurements at multiple frequencies enable separating the primary CMB anisotropies with other signals like CMB lensing, thermal and kinematic Sunyaev-Zel'dovich effects (tSZ and kSZ), and cosmic infrared background (CIB). In this paper, we explore another signal of interest at these frequencies that should be present in the CMB maps: extragalactic CO molecular rotational line emissions, which are the most widely used tracers of molecular gas in the line intensity mapping experiments. Using the SIDES simulations adopted for top hat bandpasses at 150 and 220 GHz, we show that the cross-correlation of the CIB with CO lines has a contribution similar to the CIB-tSZ correlation and the kSZ power, thereby contributing a non-negligible amount to the total power at these scales. This signal, therefore, may significantly impact the recently reported $\ge 3\sigma$ detection of the kSZ power spectrum from the South Pole Telescope (SPT) collaboration, as the contribution of the CO lines is not considered in such analyses. Our results also provide a new way of measuring the CO power spectrum in cross-correlation with the CIB. Finally, these results show that the CO emissions present in the CMB maps will have to be accounted for in all the CMB auto-power spectrum and cross-correlation studies involving a LSS tracer.

8 pages main text and bibliography + 2 pages appendices, 6 figures. Comments very welcome

References in corpus (13)

• The Herschel view of the dominant mode of galaxy growth from z=4 to the present day
• Evolution of the dust emission of massive galaxies up to z=4 and constraints on their dominant mode of star formation
• CO excitation of normal star forming galaxies out to z=1.5 as regulated by the properties of their interstellar medium
• A measurement of secondary cosmic microwave background anisotropies from the 2500-square-degree SPT-SZ survey
• Carbon monoxide line emission as a CMB foreground: tomography of the star-forming universe with different spectral resolutions
• Line-Intensity Mapping: Theory Review
• Modelling CO emission from hydrodynamic simulations of nearby spirals, starbursting mergers, and high-redshift galaxies
• An Intensity Mapping Detection of Aggregate CO Line Emission at 3 mm
• CONCERTO: High-fidelity simulation of millimeter line emissions of galaxies and [CII] intensity mapping
• Constraining the Baryon Abundance with the Kinematic Sunyaev-Zel'dovich Effect: Projected-Field Detection Using Planck, WMAP, and unWISE
• Bispectrum of the Sunyaev-Zel'dovich Effect
• An alternate approach to measure specific star formation rates at 2<z<7
• Baryon Pasting Algorithm: Halo-based and Particle-based Pasting Methods

Cited by in corpus (4)

• The Atacama Cosmology Telescope: DR6 Power Spectrum Foreground Model and Validation
• On the contributions of extragalactic CO emission lines to ground-based CMB observations
• SPECTER: An Instrument Concept for CMB Spectral Distortion Measurements with Enhanced Sensitivity
• Optimisation-based alignment of wideband integrated superconducting spectrometers for sub-mm astronomy