Tuesday, April 27, 2021

Arp 271 pair galaxies

Arp 271 (also known as NGC 5426/5427, VV 21, amongst plenty other designations) is a pair of interacting galaxies, located at a distance of around 130 million light years in the constellation of Virgo. It was discovered on the 5th of March 1785 by William Herschel.

The two galaxies are known individually as NGC 5426 and NGC 5427, and morphologically, both are spiral galaxies. The two galaxies have nearly identical imasses, at 34 and 31 trillion solar masses respectively. Thus, the pair falls into the category of “twin galaxies”. The only difference between the two, is that NGC 5427 is a Seyfert II galaxy.

Optical images have revealed the presence of a bridge-like structure that connects the two galaxies that consists of ionized gas and stars. This region displays a higher emission and a higher rate of star formation when compared with the galactic disks of the Arp 271 galaxies. 

According to data analysis and based on the properties of the H II regions within the bridge, it has been suggested that this structure is associated with NGC 5426.

Finally, it should be mentioned that according to observations, it is still not clear if the galaxies will eventually merge. Their interaction will continue for sure over the next millions of years, thus they will continue forming new stars.

Image: Composite optical image of Arp 271 taken with ESO’s VLT. NGC 5426 is on the right side of the image, while NGC 5427 is on the left. The image was created using broadband filters that are centred at 447 nm (B-band, blue), 640 nm (V-band, green), and 750 nm (R-band, red). This image was the last one that was taken with the VIsible Multi-Object Spectrograph (VIMOS) on the 24th of March 2018. It was decommissioned after 16 years of service.

Image Credit: ESO/Juan Carlos Muñoz

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