منابع مشابه
The 21-cm signature of the first stars during the Lyman–Werner feedback era
The formation of the first stars is an exciting frontier area in astronomy. Early redshifts (z ∼ 20) have become observationally promising as a result of a recently recognized effect of a supersonic relative velocity between the dark matter and gas. This effect produces prominent structure on 100 comoving Mpc scales, which makes it much more feasible to detect 21-cm fluctuations from the epoch ...
متن کاملThe 21cm Signature of the First Stars
We predict the 21-cm signature of the first metal-free stars. The soft X-rays emitted by these stars penetrate the atomic medium around their host halos, generating Lyα photons that couple the spin and kinetic temperatures. These creates a region we call the Lyα sphere, visible in 21-cm against the CMB, which is much larger than the HII region produced by the same star. The spin and kinetic tem...
متن کاملThe First Light seen in the redshifted 21–cm radiation
We show how the investigation of the redshifted 21–cm radiation can give insight into the development of structures in the early universe (at redshifts z > 5). In particular we investigate: the epoch of the first light; the fluctuations in the redshifted 21–cm emission induced by the density inhomogeneities in CDM dominated universes; the emission and absorption shells that are generated around...
متن کاملefl students gender and socioeconomic status: the use of politeness strategies in the first and second languages
within the components of communicative competence, a special emphasis is put on the “rules of politeness,” specifically the politeness strategies (brown and levinson, 1978) that speakers deploy when performing the request speech act. this is because the degree of imposition that making a request places upon one’s interlocutor(s) has been seen to be influenced by several factors among which, as ...
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ژورنال
عنوان ژورنال: The Astrophysical Journal
سال: 2008
ISSN: 0004-637X,1538-4357
DOI: 10.1086/528941