Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Detecting Early Galaxies Through Their 21-cm Signature   New observations over the next few years of the emission of distant objects
will help unfold the chapter in cosmic history around the era of the first
galaxies. These observations will use the neutral hydrogen emission or
absorption at a wavelength of 21-cm as a detector of the hydrogen abundance. We
predict the signature on the 21-cm signal of the early generations of galaxies.
We calculate the 21-cm power spectrum including two physical effects that were
neglected in previous calculations. The first is the redistribution of the UV
photons from the first galaxies due to their scattering off of the neutral
hydrogen, which results in an enhancement of the 21-cm signal. The second is
the presence of an ionized hydrogen bubble near each source, which produces a
cutoff at observable scales. We show that the resulting clear signature in the
21-cm power spectrum can be used to detect and study the population of galaxies
that formed just 200 million years after the Big Bang.

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The categories of this paper are: math
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn