Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The cosmological evolution of colour gradients in spheroids   The analysis of the four-colour maps of galaxies in the Hubble Deep Field has
revealed in the sample of 0.4<z<1 early-type field galaxies the existence of
ellipticals with a predominantly old coeval stellar population. However, there
is another, unexpected, category of HDF early-type galaxies, in which the
galaxy core is significantly bluer than the outer regions. We demonstrate that
these colour gradients are predicted by the multi-zone chemodynamical model for
the evolution of elliptical galaxies. We suggest that the colour gradient could
be used as a chronometer of the evolution of elliptical galaxies: galaxies
younger than a few Gyr exhibit cores bluer than the surrounding galaxy, due to
ongoing star formation, while more evolved galaxies have redder cores, due to
metallicity gradients increasing towards the centre.

27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
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
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys