Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Structure of Supervoids -- I: Void Hierarchy in the Northern Local
  Supervoid   Supervoids are regions in the local Universe which do not contain rich
clusters of galaxies. We have studied the closest example, the Northern Local
Void, situated between the Local, Coma, and the Hercules superclusters. We find
that this supervoid is not empty, but it contains small galaxy systems and poor
clusters of galaxies. We study the cosmography of this void by analyzing the
distribution of poor clusters of galaxies, elliptical and other galaxies in two
projections. We present a catalogue of voids, defined by galaxies of different
morphological type and luminosity, and analyze mean diameters of voids in
different environments. The sizes of voids and the properties of void walls are
related. Voids defined by poor clusters of galaxies and by bright elliptical
galaxies have a mean diameter of up to 40 h-1 Mpc. Faint late-type galaxies
divide these voids into smaller voids. The faintest galaxies we can study are
outlining voids with mean diameters of about 8 h-1 Mpc. Voids located in a
high-density environment are smaller than voids in low-density regions. This
analysis shows that voids form a hierarchical system.

27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an