  We studied the global characteristics of dust emission in a large sample of
emission-line star-forming galaxies. The sample consists of two subsamples. One
subsample (SDSS sample) includes ~4000 compact star-forming galaxies from the
SDSS, which were also detected in all four bands at 3.4, 4.6, 12, and 22 mum of
the WISE all-sky survey. The second subsample (Herschel sample) is a sample of
28 compact star-forming galaxies observed with Herschel in the FIR range. Data
of the Herschel sample were supplemented by the photometric data from the
Spitzer observations, GALEX, SDSS, WISE, 2MASS, NVSS, and FIRST surveys, as
well as optical and Spitzer spectra and data in sub-mm and radio ranges. It is
found that warm dust luminosities of galaxies from the SDSS sample and cold and
warm dust luminosities of galaxies from the Herschel sample are strongly
correlated with Hbeta luminosities, which implies that one of the main sources
of dust heating in star-forming galaxies is ionising UV radiation of young
stars. Using the relation between warm and cold dust masses for estimating the
total dust mass in star-forming galaxies with an accuracy better than ~0.5 dex
is proposed. On the other hand, it is shown for both samples that dust
temperatures do not depend on the metallicities. The dust-to-neutral gas mass
ratio strongly declines with decreasing metallicity, similar to that found in
other studies of local emission-line galaxies, high-redshift GRB hosts, and
DLAs. On the other hand, the dust-to-ionised gas mass ratio is about one
hundred times as high implying that most of dust is located in the neutral gas.
It is found that thermal free-free emission of ionised gas in compact
star-forming galaxies might be responsible for the sub-mm emission excess. This
effect is stronger in galaxies with lower metallicities and is also positively
affected by an increased star-formation rate.
