Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Restarting activity in radio galaxies   We present observations of two radio galaxies, J1835+620 and 3C338, both with
signs of having passed through different stages of core activity. The former
presents two symmetric and bright components within a typical FR II structure,
possibly resulting from two distinct phases of activity; the latter is a FR I
radio galaxy with two separated regions with different age properties, possibly
due to a switch-off and -on cycle in its core. In both sources, the optical
counterpart lies in a group of galaxies with indications of mutual interaction,
a scenario often invoked to explain triggering of core activity.

36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex