Washington: ESO's Multi Unit Spectroscopic Explorer (MUSE) instrument have provided scientists with the best yet view of spectacular cosmic crash, revealing the true story behind it.
A team of researchers led by Michele Fumagalli from Durham University, were among the first to use MUSE instrument, and observe ESO 137-001, a spiral galaxy 200 million light-years away in the southern constellation of Triangulum Australe (The Southern Triangle). They were able to get the best view so far of exactly what is happening to the galaxy as it hurtles into the Norma Cluster.
MUSE gives astronomers not just a picture, but provides a spectrum, or a band of colours, for each pixel in the frame. With this instrument researchers collect about 90 000 spectra every time they look at an object, and thereby record a staggeringly detailed map of the motions and other properties of the observed objects.
ESO 137-001 is being robbed of its raw materials by a process called ram-pressure stripping, which happens when an object moves at high speed through a liquid or gas. The gas is part of the vast cloud of very thin hot gas that is enveloping the galaxy cluster into which ESO 137-001 is falling at several million kilometers per hour.
The galaxy is being stripped of most of its gas-the fuel needed to make the next generations of young blue stars. ESO 137-001 is in the midst of this galactic makeover, and is being transformed from a blue gas-rich galaxy to a gas-poor red one.
With the help of MUSE, which is mounted on one of the VLT's 8-metre Unit Telescopes at the Paranal Observatory in Chile, scientists could not only detect the gas in and around the galaxy, but were able to see how it moves. The new instrument has been so efficient that a single hour of observing time was sufficient to obtain a high resolution image of the galaxy as well as the distribution and motion of its gas.
The observations showed that the outskirts of ESO 137-001 were already completely devoid of gas as a result of the cluster gas. This happened first in the spiral arms where the stars and matter were more thinly spread than at the centre, and gravity had only a relatively weak hold over the gas. In the centre of the galaxy, however, the gravitational pull was strong enough to hold out longer in the cosmic tug-of-war and gas was still observed.
Eventually, all of the galactic gas would be swept away into bright streaks behind ESO 137-001, telltale remnants of this dramatic robbery. The gas that was torn away from the galaxy was mixed with the hot cluster gas to form magnificent tails extending to a distance of over 200 000 light-years.
Surprisingly the new MUSE observations of this gas plume show that the gas continues to rotate in same way the galaxy does, even after being swept out into space. Furthermore, researchers were able to determine that the rotation of stars in ESO 137-001 remains unchanged. This provided further evidence for the cluster gas, not gravity, being responsible for stripping the galaxy.
