Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Structure of Galaxies at Faint Light Levels: Probing Galaxy Assembly   Many clues about the galaxy assembly process lurk in the faint outer regions
of galaxies. Although quantitative study of these parts has been severely
limited in the past, breakthroughs are now being made thanks to the combination
of wide-area star counts, deep HST imagery and 8-m class spectroscopy. I
highlight here some recent progress made on deciphering the fossil record
encoded in the outskirts of our nearest large neighbours, M31 and M33.

20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
3
The categories of this paper are: physics