Intensity mapping of H-alpha, H-beta, [OII] and [OIII] lines at z<5

TL;DR

This paper explores the potential of intensity mapping of key emission lines like H-alpha, H-beta, [OII], and [OIII] at redshifts below 5 to study large-scale structure and star formation history, using simulations and upcoming missions.

Contribution

It provides new estimates of line intensities, power spectra, and star formation rate density constraints from intensity mapping at z<5, including foreground contamination and cross-correlation analysis.

Findings

Auto and cross power spectra measurable for H-alpha, [OIII], [OII] at z<3

Potential to constrain star formation rate density with better than 7% accuracy at z<4

Intensity mapping can outperform traditional galaxy luminosity function methods

Abstract

Intensity mapping is now becoming a useful tool to study the large-scale structure of the universe through spatial variations in the integrated emission from galaxies and the intergalactic medium. We study intensity mapping of the H-alpha 6563AA, [OIII]5007AA, [OII]3727AA and H-beta 4861AA lines at 0.8<z<5.2. The mean intensities of these four emission lines are estimated using the observed luminosity functions (LFs), cosmological simulations, and the star formation rate density (SFRD) derived from observations at z<5. We calculate the intensity power spectra and consider the foreground contamination of other lines at lower redshifts. We use the proposed NASA small explorer SPHEREx (the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer) as a case study for the detectability of the intensity power spectra of the four emission lines. We also investigate the cross correlation with the 21-cm line probed by CHIME (the Canadian Hydrogen Intensity Mapping Experiment), Tianlai experiment and SKA (the Square Kilometer Array) at 0.8<z<2.4. We find both the auto and cross power spectra can be well measured for the H-alpha, [OIII] and [OII] lines at z<3, while it is more challenging for the H-beta line. Finally, we estimate the constraint on the SFRD from intensity mapping, and find we can reach accuracy higher than 7% at z<4, which is better than usual measurements using the LFs of galaxies.