The study of gas movement in 20 nearby spiral galaxies has unveiled a definite difference between those with bars and those without bars. Such a thing indicates that already available information on gas movement can be utilized to examine bars in spiral galaxies, even if it’s not in high-resolution imaging data.
A team of scientists discovered a new procedure to examine barred spiral galaxies. Here is what it found.
The Spiral Situation Re-examined
In spiral galaxies, a massive disc of stars and gas revolves around a central point. Spiral galaxies are named like this because they have bright swirls (spiral arms) in the disc where stars are more concentrated. Lots of types of spirals have been spotted, including some with straight sections, dubbed bars.
However, a galactic disc is not a solid object—various parts of the disc twist at different rates, similar to the clouds in a typhoon. The movement in a galactic disc isn’t restricted to the circular rotation, parts moving radially away from or towards the center can also be seen.
To better comprehend movement within the disk, a team of scientists examined the gas movement in the discs for a sample of 20 nearby spiral galaxies, including seven barred spirals. They discovered a definite difference between the kinematics of non-barred and barred galaxies.
Barred spirals have an average 1.5-2 times more radial movement than non-barred spirals out to the end of the bar, but over the end of the bar, the movement is almost circular. As for the non-barred spiral galaxies, they display little radial motion at all locations. This result resembles theoretical models where the bar formation helps to direct gas towards the center of the galaxy.
The team also discovered that the radius where the movement towards the center ceases is somehow related to the dimension of the bar, between 0.8 to 1.6 times the length. Such a thing indicates that utilizing the gas movement as a proxy for the bar could support scientists to use modest-resolution, wide-field speed information, which is more accessible than high-resolution image data.