Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Galaxy systems in the optical and infrared   In these three lectures a review is provided of the properties of galaxy
systems as determined from optical and infrared measurements. Covered topics
are: clusters identification, global cluster properties and their scaling
relations, cluster internal structure and dynamics, and properties of cluster
galaxy populations.

20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga