Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Compared Number Density of High-Redshift Galaxies and Lyman \alpha
  Clouds   We use our catalog of photometric redshifts in the Hubble Deep Field (HDF) to
estimate the Luminosity Function (LF) of galaxies up to z=2. Using the obtained
LF and a relationship between luminosity and halo size, we calculate the
expected density of galactic halo crossings for any arbitrary line of sight.
This density is then compared with the known one of Lyman \alpha lines, showing
that the observed density of galaxies is enough to account for the observed
absorption lines.

15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
4
The categories of this paper are: cond-mat
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs