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