Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The unification of powerful quasars and radio galaxies and their
  relation to other massive galaxies   The unification model for powerful radio galaxies and radio-loud quasars
postulates that these objects are intrinsically the same but viewed along
different angles. Herschel Space Observatory data permit the assessment of that
model in the far-infrared spectral window. We analyze photometry from Spitzer
and Herschel for the distant 3CR hosts, and find that radio galaxies and
quasars have different mid-infrared, but indistinguishable far-infrared colors.
Both these properties, the former being orientation dependent and the latter
orientation invariant, are in line with expectations from the unification
model. Adding powerful radio-quiet active galaxies and typical massive
star-forming galaxies to the analysis, we demonstrate that infrared colors not
only provide an orientation indicator, but can also distinguish active from
star-forming galaxies.

24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat