This SALT image is of the spiral galaxy, NGC5364, a member of the Virgo cluster, at a distance of ~70 million light years. It was taken with the Robert Stobie Spectrograph (RSS) on SALT during the commissioning of its Fabry-Perot mode, in May 2011. The light is from the H-alpha emission line of neutral hydrogen gas, which is seen in the spiral arms where young hot stars are found and are still forming out of the gas.

The false colours in this image are coded on the wavelength of the peak of the H-alpha emission line, which is Doppler shifted because of the rotation of the galaxy. The bluer colours reflect blueshifted light from gas in the galaxy that is moving towards us, while the red comes from the receding, redshifted, gas. The green colour is from gas which is at intermediate velocities.

Posted: 16 June 2011