A Submillimeter Galaxy (SMG, or Submillimeter-Selected Galaxy or Dusty Star-Forming Galaxy, i.e., DSFG) is a Galaxy viewed mostly through submillimeter radiation. These include high Redshift galaxies. Specifically, the 850 um Flux density is generally greater than 3-5 millijanskies. They are very luminous because of Star Formation rather than because they are Active Galactic Nucleus galaxies. The spectrum typically seen is Black-Body Radiation from Dust grains and Emission Lines from the gas in the Interstellar Medium.
An SMG is typically a massive starburst high-redshifted Elliptical Galaxy.
Spectral Flux Density (S)
Submillimeter Galaxy Designator