Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cosmic histories of star formation and reionization: An analysis with a
  power-law approximation   With a simple power-law approximation of high-redshift ($\gtrsim3.5$) star
formation history, i.e., $\dot{\rho}_*(z)\propto [(1+z)/4.5]^{-\alpha}$, we
investigate the reionization of intergalactic medium (IGM) and the consequent
Thomson scattering optical depth for cosmic microwave background (CMB) photons.
A constraint on the evolution index $\alpha$ is derived from the CMB optical
depth measured by the {\it Wilkinson Microwave Anisotropy Probe} (WMAP)
experiment, which reads $\alpha\approx2.18\lg{\mathscr{N}_{\gamma}}-3.89$,
where the free parameter $\mathscr{N}_\gamma$ is the number of the escaped
ionizing ultraviolet photons per baryon. Moreover, the redshift for full
reionization, $z_f$, can also be expressed as a function of $\alpha$ as well as
$\mathscr{N}_{\gamma}$. By further taking into account the implication of the
Gunn-Peterson trough observations to quasars for the full reionization
redshift, i.e., $6\lesssim z_f \lesssim7$, we obtain
$0.3\lesssim\alpha\lesssim1.3$ and $80\lesssim\mathscr{N}_{\gamma}\lesssim230$.
For a typical number of $\sim4000$ of ionizing photons released per baryon of
normal stars, the fraction of these photons escaping from the stars, $f_{\rm
esc}$, can be constrained to within the range of $(2.0-5.8)%$.

12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga