New high-resolution ALMA data reveal the shapes and sizes of actively star-forming submillimetre galaxies

The discovery of the first galaxies identified by the light that they emit at at sub-millimetre wavelengths (SMGs) in 1997 fundamentally changed our view of galaxy formation. These galaxes are rapidly forming new stars this, plus their masses and sizes are challenging to reproduce for galaxy formation models. SMGs provide a new window through which to study the formation and evolution of extreme star-forming galaxies only a few billions years after the Big Bang.

Some of the key properties to measure are the sizes and shapes of these galaxies. To measure such parameters accurately we need high resolution observations. Up until a few years ago this was not possible, but with the Atacama Large Millimeter/Submillimeter Array (ALMA) - a new telescope in Chile - we are now able to see details in these galaxies, which allow us to determine the sizes and shapes.

Durham astronomers have now observed four SMGs with ALMA and have obtained observations at unprecedentedly high resolution. These new observations show that the SMGs have sizes similar to that of the nearby Large Magellanic Cloud but that they contain more gas and dust, which is turned into stars more than 1000 times faster than the Large Magellanic Cloud. The observations also show that, though SMGs were expected to have messy shapes, these four SMGs can be described as smooth discs.

Images of two of the SMGs studied, from low to high resolution (bottom to top)
This figure shows two of the four SMGs that we studied. The bottom row shows low resolution observations, the middle row intermediate resolution, and the top row the highest resolution observations. The highest resolution observations seem to show some structure in the shapes, but these apparent structures are likely to be artefacts in the observations.

Link to the original research paper:

Contacts from CEA, Durham:

Bitten Gullberg

Mark Swinbank

Ian Smail

Elizabeth Cooke

Alastair Edge

Stuart Stach

Julie Wardlow