نتایج جستجو برای: radiocarbon dating
تعداد نتایج: 18604 فیلتر نتایج به سال:
Continuum observations at radio, millimetre, infrared and soft X-ray energies are presented for a sample of 22 quasars, consisting of flat and steep spectrum radio loud, radio intermediate and radio quiet objects. The primary observational distinctions, among the different kinds of quasars in the radio and IR energy domains are studied using large observational datasets provided by ISOPHOT on b...
Using a sample of more than 6000 quasars from the Sloan digital sky survey (SDSS) we compare the black-hole mass distributions of radio-loud and radio-quiet quasars. Based on the virial black-hole mass estimator the radio-loud quasars (RLQs) are found to harbour systematically more massive black holes than radio-quiet quasars (RQQs) with very high significance (≫ 99.99%), with mean black-hole m...
We report on a search for ultra-high-energy (UHE) neutrinos from gamma-ray bursts (GRBs) in the data set collected by the Testbed station of the Askaryan Radio Array (ARA) in 2011 and 2012. From 57 selected GRBs, we observed no events that survive our cuts, which is consistent with 0.12 expected background events. Using NeuCosmA as a numerical GRB reference emission model, we estimate upper lim...
Atmospheric conditions at Chajnantor have been monitored since April 1995. Starting then, the National Radio Astronomy Observatory (NRAO), joined by the European Southern Observatory (ESO), Onsala Space Observatory (OSO), and the Nobeyama Radio Observatory (NRO), have operated atmospheric and weather monitoring equipment to characterize the observing conditions for a large radio interferometer ...
We present a complete sample of 24 radio-loud quasars (RLQs) from the new 7C Redshift Survey. Every quasar with a low-frequency (151 MHz) radio flux-density S151 > 0.5 Jy in two regions of the sky covering 0.013 sr is included; 23 of these have sufficient extended flux to meet the selection criteria, 18 of these have steep radio spectra (hereafter denoted as SSQs). The key advantage of this sam...
In this paper we investigate how the Square Kilometre Array (SKA) can aid in determining the evolutionary history of active galactic nuclei (AGN) from redshifts z = 0→ 6. Given the vast collecting area of the SKA, it will be sensitive to both ‘radio-loud’ AGN and the much more abundant ‘radio-quiet’ AGN, namely the radio-quiet quasars and their ‘Type-II’ counterparts, out to the highest redshif...
This paper deals with the various assumptions used in the design and analysis of distributed antenna system (DAS) for trains, tunnels and in-building wireless radio coverage. The design includes handover overlap design, base station connectivity, signal reticulation using splitters, couplers, bidirectional amplifiers, attenuators, discrete antennas, radiating cables and opto-electric couplers e...
We present the results of a deep K-band imaging study which reveals the host galaxies around a sample of 14 luminous radio-quiet quasars. The K-band images, obtained at UKIRT, are of sufficient quality to allow accurate modelling of the underlying host galaxy. Initially, the basic structure of the hosts is revealed using a modified Clean deconvolution routine optimised for this analysis. Two of...
We analyze the time evolution of microwave spectral indices for 103 solar flares observed by Nobeyama Radio Polarimeters (NoRP) between 1998 and 2005. The microwave spectral index, .t/, is derived from the flux spectral index, ı.t/. We assume a flux frequency dependence of the form S. ;t/=F0 ı.t/ in the optically thin part, i.e., above the turnover frequency, fmax. Here, fmax is defined as the ...
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