Galaxy Groups Hiding in the Universe's Emptiest Places

• The CAVITY (Calar Alto Void Integral field Treasury surveY) study reveals that cosmic voids—the universe's vast, empty regions—still harbor small, loose collections of galaxies.
• Using a "friends of friends" algorithm, researchers identified 1,367 bound groups consisting of 3,040 galaxies within these voids, alongside 14,672 solitary galaxies.

Findings on Void Galaxy Structures

• Voids actively discourage galaxy grouping: 59% of void galaxies are solitary, whereas in control samples outside voids, 60% of galaxies belong to groups.
• Void groups are dynamically "youthful" and loosely bound, lacking the settled, well-mixed structure of clusters in denser regions.
• The densest groups found within these voids contain only six galaxies.
• Group richness in voids is independent of the void's depth; deep voids can host groups as easily as shallow ones.

Implications

• Voids are not completely barren; gravity persists in pulling galaxies together, though the process is incomplete and slower than elsewhere.
• Research suggests that even in the universe's loneliest neighborhoods, sparse but organized social groupings of galaxies exist.