An image captured by the Hubble Space Telescope shows Arp 107, a pair of interacting galaxies heading towards a collision. The two galaxies, the spiral galaxy UGC 5984 (or PGC 32620) and the elliptical galaxy MCG +05-26-025 (or PGC 32628), will finish this process in a merger. UGC 5984 is a Seyfert galaxy, a class characterized by an active galactic nucleus that doesn’t block the view of the rest of the galaxy and spectral lines that show a strong ionization. The pair represents an interesting case of the early phase of a galaxy merger.
About 465 million light-years away from Earth, the Arp 107 pair is included in the Atlas of Peculiar Galaxies precisely because the two galaxies that compose it are close enough to distort the shape of the largest one, UGC 5984. It can still be seen clearly that it’s a spiral galaxy with a colossal arm surrounding its nucleus. However, the side oriented towards the neighbor already shows the effects of its gravity with a sort of gas bridge that now unites the two galaxies and in some areas gas and dust are bright.
The galaxy UGC 5984 represents an interesting object of study because it’s a Seyfert galaxy. Active galactic nuclei are extremely bright due to the very strong electromagnetic emissions generated by the heating of the materials surrounding the central supermassive black hole. Typically, this prevents us from seeing the rest of the galaxy but this doesn’t happen in the case of Seyfert galaxies and this helps to study the consequences of the influence of the activity of the nucleus, for example on star formation.
The galaxy MCG +05-26-025 is decidedly smaller than its neighbor, with a bright nucleus and little else as some dispersed gas can be seen in its vicinity. For now, we see that compact galaxy still with a defined shape but the interaction with its neighbor will cause it to distort, as its gravitational attraction increases with its approach.
The Hubble Space Telescope’s Advanced Camera for Surveys (ACS) instrument captured several photos that were assembled into one image of the Arp 107 pair but the indications of the colors and filters used to create it reveal that photos captured during the Sloan Digital Sky Survey (SDSS) and the DECam mounted on the Víctor M. Blanco telescope were also used. This allows to obtain the best possible image of these interacting galaxies within a program that presents unusual galaxies to the public. This is useful information for astronomers to study galaxy mergers, normal events in the evolution of galaxies and therefore important.
