Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Complete Star Formation History of the Universe   The determination of the star-formation history of the Universe is a key goal
of modern cosmology, as it is crucial to our understanding of how structure in
the Universe forms and evolves. A picture has built up over recent years,
piece-by-piece, by observing young stars in distant galaxies at different times
in the past.
  These studies indicated that the stellar birthrate peaked some 8 billion
years ago, and then declined by a factor of around ten to its present value.
Here we report on a new study which obtains the complete star formation history
by analysing the fossil record of the stellar populations of 96545 nearby
galaxies. Broadly, our results support those derived from high-redshift
galaxies elsewhere in the Universe. We find, however, that the peak of star
formation was more recent - around 5 billion years ago. Our study also shows
that the bigger the stellar mass of the galaxy, the earlier the stars were
formed. This striking result indicates a very different formation history for
high- and low-mass formation.

14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math