Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Structure of High Redshift Galactic Halos   Observations of multiple or lensed QSOs at high redshift can be used to probe
transverse structure in intervening absorption systems. Here we present results
obtained from STIS spectroscopy of the unique triply imaged QSO APM08279+5255
at z = 3.9 and study the coherence scales of intervening low and high
ionization absorbers.

2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org