Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Age and metallicity gradients in early-type galaxies: A dwarf to giant
  sequence
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con