The NGC 3640 Galaxy Group: Wide-field view | ESO

The NGC 3640 Galaxy Group: Wide-field view | ESO

The Very Large Survey Telescope (VST) has captured here an entire zoo of galaxies, filling the empty void of space. At the center of this varied and colorful collection, is elliptical galaxy NGC 3640, situated just above its smaller galactic neighbor NGC 3641. Astronomers are especially interested in the way these two interact with each other, studying their joint history through their populations of ancient clusters of stars.

Distance: 88 million light-years

Throughout their extremely long lifetime, galaxies change. As they soar through space, they may steal gas and stars from other galaxies, or even engulf and merge with them. After these events, galaxies can become distorted, as exemplified by the misshaped NGC 3640 and the diffuse light around it. The galaxy is then left with ‘scars’ that hint at a violent past. Astronomers can use these to know its past and present history.

To trace the history behind this galaxy and its smaller companion, a team of astronomers at the Italian National Institute for Astrophysics used the VST to analyze their globular clusters, spherical and compact aggregations of stars bound by gravity. These usually contain examples of the first stars created within a galaxy and can therefore act as fossil markers, revealing the galaxy’s history, even after merging events.

The results confirm that NGC 3640 has engulfed other galaxies before, an ominous sign for the smaller galaxy now in its path, NGC 3641. Yet, this small galactic underdog shows a distinct lack of distortions in its shape or the globular clusters within. This suggests that their interaction, while fast, is not happening close enough for NGC 3640 to pose a threat. NGC 3641 might be safe . . . for now.

Credit: ESO/INAF/M. Mirabile et al./R. Ragusa et al.
Release Date: Feb. 17, 2024

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