  We use the Herschel-ATLAS survey to conduct the first large-scale statistical
study of the submm properties of optically selected galaxies. Using ~80,000
r-band selected galaxies from 126 deg^2 of the GAMA survey, we stack into submm
imaging at 250, 350 and 500{\mu}m to gain unprecedented statistics on the dust
emission from galaxies at z < 0.35. We find that low redshift galaxies account
for 5% of the cosmic 250{\mu}m background (4% at 350{\mu}m; 3% at 500{\mu}m),
of which approximately 60% comes from 'blue' and 20% from 'red' galaxies
(rest-frame g - r). We compare the dust properties of different galaxy
populations by dividing the sample into bins of optical luminosity, stellar
mass, colour and redshift. In blue galaxies we find that dust temperature and
luminosity correlate strongly with stellar mass at a fixed redshift, but red
galaxies do not follow these correlations and overall have lower luminosities
and temperatures. We make reasonable assumptions to account for the
contaminating flux from lensing by red sequence galaxies and conclude that
galaxies with different optical colours have fundamentally different dust
emission properties. Results indicate that while blue galaxies are more
luminous than red galaxies due to higher temperatures, the dust masses of the
two samples are relatively similar. Dust mass is shown to correlate with
stellar mass, although the dust/stellar mass ratio is much higher for low
stellar mass galaxies, consistent with the lowest mass galaxies having the
highest specific star formation rates. We stack the 250{\mu}m/NUV luminosity
ratio, finding results consistent with greater obscuration of star formation at
lower stellar mass and higher redshift. Submm luminosities and dust masses of
all galaxies are shown to evolve strongly with redshift, indicating a fall in
the amount of obscured star formation in ordinary galaxies over the last four
billion years.
