Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: New light on the formation and evolution of bars: Trends in the stellar
  line-strength indices distribution inside the bar region   Aim: The aim is to study the stellar content of the bar region to constrain
its formation and evolution. Methods: Line-strength indices in the bar region
of a sample of 6 barred galaxies were employed to derive age and metallicity
gradients along the bars using stellar population models. Results: We find
clear radial gradients in the line-strength indices for all the galaxies. We
find positive gradients within the bar region in the metal indices in four of
the six galaxies, and opposite trends in the other two. These latter two
galaxies are classified as SAB and they present exponential bar light profiles.
For all the galaxies we find a positive gradient in the Balmer indices. There
is a clear correlation between the position of morphological features inside
the bar region with changes in the slope and value of the indices, which
indicate, using stellar population analysis, changes in the stellar
populations. Therefore, it seems that the bar regions show a gradient in both
age and metallicity, changing radially to younger and more metal rich
populations for all the galaxies except for those two with exponential
profiles.

32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex