Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radiation from early black holes - I: effects on the neutral
  inter-galactic medium   In the pre-reionization Universe, the regions of the inter-galactic medium
(IGM) which are far from luminous sources are the last to undergo reionization.
Until then, they should be scarcely affected by stellar radiation; instead, the
X-ray emission from an early black hole (BH) population can have much larger
influence. We investigate the effects of such emission, looking at a number of
BH model populations (differing for the cosmological density evolution of BHs,
the BH properties, and the spectral energy distribution of the BH emission). We
find that BH radiation can easily heat the IGM to 10^3-10^4 K, while achieving
partial ionization. The most interesting consequence of this heating is that
BHs are expected to induce a 21-cm signal (delta T_b ~ 20-30 mK at z<~12) which
should be observable with forthcoming experiments (e.g. LOFAR). We also find
that at z<~10 BH emission strongly increases the critical mass separating
star-forming and non-star-forming halos.

23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
12
The categories of this paper are: nucl-th