Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lyman Break Galaxies in the NGST Era   With SIRTF and NGST in the offing, it is interesting to examine what the
stellar populations of z~3 galaxies models imply for the existence and nature
of Lyman-break galaxies at higher redshift. To this end, we ``turn back the
clock'' on the stellar population models that have been fit to optical and
infrared data of Lyman-break galaxies at z~3. The generally young ages
(typically 10^8 +- 0.5 yr) of these galaxies imply that their stars were not
present much beyond z=4. For smooth star-formation histories SFR(t) and
Salpeter IMFs, the ionizing radiation from early star-formation in these
galaxies would be insufficient to reionize the intergalactic medium at z~6, and
the luminosity density at z~4 would be significantly lower than observed. We
examine possible ways to increase the global star-formation rate at higher
redshift without violating the stellar-population constraints at z~3.

37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol