NGC 6621 is the larger of the two, and is a very disturbed spiral galaxy. The encounter has pulled a long tail out of NGC 6621 that has now wrapped at the north behind its body. The collision has also triggered extensivestar formation between the two galaxies. The most intense star formation takes place in the region between the two nuclei, where a large population of luminousclusters, also known assuper star clusters, has been observed. At this region is observed the mosttidal stress. Many large clusters are also observed in the tail and the nucleus of NGC 6621.[4][6] The brightest and bluest clusters are less than 100 million years old, with the youngest being less than 10 million years old. The side of the galaxy further from the companion features noticeably less star formation activity.[4]
NGC 6621 is characterised as aluminous infrared galaxy, with its infrared luminosity being 1011.24L☉.[7] NGC 6621 contributes nearly all of the radio and farinfrared flux of the pair. When observed inH-alpha, the centre of the galaxy has two bright sources separated by 3 arcseconds, with the southwest being brighter while the northeastern one coincides with the nucleus of NGC 6621.[8]
^Hattori, T.; Yoshida, M.; Ohtani, H.; Sugai, H.; Ishigaki, T.; Sasaki, M.; Hayashi, T.; Ozaki, S.; Ishii, M.; Kawai, A. (February 2004). "A Study of the Distribution of Star-forming Regions in Luminous Infrared Galaxies by Means of H Imaging Observations".The Astronomical Journal.127 (2):736–757.arXiv:astro-ph/0311179.Bibcode:2004AJ....127..736H.doi:10.1086/381060.S2CID18181421.
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