Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Formation Scenarios   I discuss various proposed formation scenarios for the metal-poor components
of the Milky Way Galaxy, emphasising the stellar halo and the thick disk.
Interactions and accretion played a significant role in Galactic evolution, in
particular at earlier epochs. The present observations favour a scenario by
which the thick disk formed through the heating of a pre-existing thin stellar
disk, with the heating mechanism being the merging of a satellite galaxy. A
remnant `moving group' of the satellite would provide strong support for this
scenario, and may have been detected. The field stars in the stellar halo
probably formed in early small-scale star-forming regions, which subsequently
disrupted. Late accretion is not important for the bulk of the stellar halo.
The stellar initial mass function shows no evidence of variations, and indeed
shows evidence of being invariant, even in companion satellite galaxies.

5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
14
The categories of this paper are: math-ph