Void Hierarchy in the Northern Local Void: Faint structures in low density regions of the nearby Universe
The Northern Local Void is a huge underdense region of the nearby Universe situated between the Hercules, Coma and Local Superclusters. We present an investigation of the galaxy distribution in the Northern Local Void using void statistics. In particular galaxies of different morphological type and luminosity have been studied separately and void catalogues have been compiled from three different luminosity limited galaxy samples for the first time. Our approach is complementary to most other methods usually used in Large-Scale Structure studies and has the potential to detect and describe subtle structures in the galaxy distribution. We found that the resulting sets of voids form a hierarchical system: The fainter the limiting luminosity of the galaxies the smaller are the voids defined by them. Voids outlined by bright galaxies are interlaced by a fine network of faint galaxy filaments dividing them into smaller subvoids. This Void Hierarchy is an important property of the Large-Scale Structure in the Universe which constrains any realistic galaxy and structure formation scenario. In addition, this concept of Void Hierarchy may help to devise new concepts for the study of the Large-Scale Structure in the Universe.