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 applied the concept of superradiance introduced by Dicke in 1954 to astrophysics by extending the corresponding analysis to the magnetic dipole interaction characterizing the atomic hydrogen 21 cm line. Although it is unlikely that superradiance could take place in thermally relaxed regions and that the lack of observational evidence of masers for this transition reduces the probability...
متن کاملThe Virgo Cluster Distance from 21 Cm-line Widths
The distance of the Virgo cluster is derived in the B band from the 21 cm-line width-absolute magnitude relation. The latter is calibrated using 18 spirals with Cepheid distances mainly from HST. The calibration is applied to a complete sample of non-peculiar spirals with i > 45◦ and lying within the optical (n=49) or X-ray (n=35) contour of the cluster, resulting in a mean cluster distance of ...
متن کاملStars and reionization: the cross-correlation of the 21 cm line and the near-infrared background
With improving telescopes, it may now be possible to observe the Epoch of Reionization in multiple ways. We examine two of these observables – the excess light in the near-infrared background that may be due to high-redshift stars and ionized HII bubbles, and the 21 cm emission from neutral hydrogen. Because these two forms of emission should result from different, mutually exclusive regions, a...
متن کاملThe Millennium Arecibo 21-cm Absorption Line Survey: Extolling the Analysis Procedures
We have recently completed the analysis of a survey of the HI line in emission/absorption against 79 radio sources. Our CNM temperatures are about half those of previous authors and we find a substantial quantity of thermally unstable WNM. These results are somewhat controversial. Here we discuss the analysis procedures to illustrate explicitly why the results are reliable. Our full papers (Hei...
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ژورنال
عنوان ژورنال: Physical Review D
سال: 2019
ISSN: 2470-0010,2470-0029
DOI: 10.1103/physrevd.99.015031