Observations of the 21-cm line in dark clouds
نویسندگان
چکیده
منابع مشابه
Constraining dark matter through 21 cm observations
Beyond reionization epoch cosmic hydrogen is neutral and can be directly observed through its 21 cm line signal. If dark matter (DM) decays or annihilates the corresponding energy input affects the hydrogen kinetic temperature and ionized fraction, and contributes to the Lyα background. The changes induced by these processes on the 21 cm signal can then be used to constrain the proposed DM cand...
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We have made HI 21cm-line absorption measurements using the GMRT towards 15 directions in the Galaxy which are known to have high random velocity clouds as seen in the optical absorption lines of CaII and NaI. For the first time, in 6 out of these 15 directions we detect HI absorption features corresponding to the high random velocity optical absorption lines. The mean optical depth of these de...
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Many observations indicate that dark matter dominates the extra-galactic Universe, yet no totally dark structure of galactic proportions has ever been convincingly identified. Previously we have suggested that VIRGOHI 21, a 21-cm source we found in the Virgo Cluster using Jodrell Bank, was a possible dark galaxy because of its broad line-width (∼ 200 km s−1) unaccompanied by any visible gravita...
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The 21-cm hyperfine line of atomic hydrogen (H i) is a promising probe of the cosmic dark ages. In past treatments of 21-cm radiation it was assumed the hyperfine level populations of H i could be characterized by a velocity-independent “spin temperature” Ts determined by a competition between 21-cm radiative transitions, spin-changing collisions, and (at lower redshifts) Lyα scattering. Howeve...
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We have carried out semianalytic simulations to build redshifted 21-cm maps in the dark ages. An entropy-floor model is adopted for planting protogalaxies in simulated minihaloes. The model allocates gas quantities such as baryonic mass and temperature to every N -body particle and extensively exploits the particle nature of the data in the subsequent analysis. We have found that the number den...
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ژورنال
عنوان ژورنال: Monthly Notices of the Royal Astronomical Society
سال: 1978
ISSN: 0035-8711,1365-2966
DOI: 10.1093/mnras/185.4.755