A 3D View of a Galactic Merger

This animation shows a #D rendering of a gas halo observed by ESO’s Very Large Telescope superimposed over an older image of a galaxy merger obtained with ESO’s Atacama Large Millimeter Array. The halo of hydrogen gas is shown in blue, and the ALMA data is shown in orange. The halo is bound to the galaxy, which contains a quasar at its center. The gas in the halo provides the perfect food source for the supermassive black hole at the centre of the quasar.

The redshift on these objects is 6.2, meaning we see them as they were 12.8 billion years ago.

Video Credit: ESO

Getting to the Source

magellanic_streamBack in the 1970s, radio astronomers detected a band of gas that wrapped almost half way around our Milk Way galaxy. Since the origin seemed to be in one or the other of the Large and Small Magellanic Clouds, two nearby satellite galaxies, the gas was named the Magellanic Stream. Recent observations using the Hubble Space Telescope have sources of the gas stream.

Most of the gas was stripped from the Small Magellanic Cloud about 2 billion years ago, but a second region of the stream originated more recently from the Large Magellanic Cloud. This was determined by using Hubble‘s Cosmic Origins Spectrograph to measure the amount of heavy elements, such as oxygen and sulfur, at six locations along the Magellanic Stream. The heavy elements were detected by their absorption of ultraviolet light from distant quasars. There was a low amount of oxygen and sulfur along most of the stream, matching the levels in the Small Magellanic Cloud roughly 2 billion years ago, when the gaseous ribbon is thought to have formed, but there are much higher level of sulfur in a region of the stream that is closer to the Magellanic Clouds, suggesting that the Large Cloud may be a more recent source too.

Image Credit: NASA