  In this work we model the observed evolution in comoving number density of
Lyman-alpha blobs (LABs) as a function of redshift, and try to find which
mechanism of emission is dominant in LAB. Our model calculates LAB emission
both from cooling radiation from the intergalactic gas accreting onto galaxies
and from star formation (SF). We have used dark matter (DM) cosmological
simulation to which we applied empirical recipes for Ly$\alpha$ emission
produced by cooling radiation and SF in every halo. In difference to the
previous work, the simulated volume in the DM simulation is large enough to
produce an average LABs number density. At a range of redshifts $z\sim 1-7$ we
compare our results with the observed luminosity functions of LABs and LAEs.
Our cooling radiation luminosities appeared to be too small to explain LAB
luminosities at all redshifts. In contrast, for SF we obtained a good agreement
with observed LFs at all redshifts studied. We also discuss uncertainties which
could influence the obtained results, and how LAB LFs could be related to each
other in fields with different density.
