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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The introduction of low-frequency radio arrays over the coming decade is expected to revolutionize the study of the reionization epoch. Observation of the contrast in redshifted 21cm emission between a large H II region and the surrounding neutral IGM will be the simplest and most easily interpreted signature. We assess the sensitivity of three generations of planned low-frequency arrays to qua...
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We report on a preliminary analysis of a 5600 sec per point survey of 32 square degrees in Centaurus, carried out with the Parkes 13-beam system. The signal-to-noise ratio is found to improve as √ tobs for the whole integration. We have detected 102 HI sources between +250 and +12,700 km s−1 either by eye or by using the new galaxy-finding algorithm PICASSO. Over half of these are new HI detect...
متن کامل21-cm Synthesis Observations of Virgohi 21 - a Possible Dark Galaxy in the Virgo Cluster
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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We present simultaneous observations by EUV E, ASCA, and RXT E of the type 1 Seyfert galaxy NGC 5548. These data indicate that variations in the EUV emission (at D0.2 keV) appear to lead similar modulations in higher energy keV) X-rays by D10È30 ks. This is contrary to popular (Z1 models which attribute the correlated variability of the EUV, UV and optical emission in type 1 Seyferts to reproce...
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ژورنال
عنوان ژورنال: Australian Journal of Physics
سال: 1967
ISSN: 0004-9506
DOI: 10.1071/ph670131