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تسجيل مستخدم جديدX-ray properties of head-tail radio sources in clusters of galaxies
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A.C. Edge H. Roettgering
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From ROSAT imaging data we have detections and upper limits for a sample of 26 tailed radio sources in clusters of galaxies mostly from the sample of ODea & Owen (1985). All sixteen of the detected sources are unresolved in the ROSAT PSPC images. The sources bright enough to perform X-ray spectral analysis have power-law indices similar to BL~Lacs and Seyfert galaxies. We find that there is a highly significant correlation between the core radio flux density and the X-ray flux but only a weak correlation between the total radio flux density and the X-ray flux. The trend is similar to that found in earlier studies of 3C radio galaxies with {sl Einstein} and more recently with ROSAT. The result adds an additional constraint on models for the unification of BL~Lac objects with FR~I radio sources. Also this result indicates that the observed enhanced X-ray emission near tailed sources is more likely to be due to nuclear emission rather than substructure in the extended cluster gas.
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The study of Head Tail (HT) radio galaxies track the information of associated galaxy clusters. With the help of the VLA FIRST survey at 1.4 GHz, we detected 607 new HT radio sources, among them, 398 are Wide Angle Tail (WAT) and 216 are Narrow-Angle
Tail (NAT) sources. NAT sources generally have `V shaped structure with an opening angle less than ninety degrees and for WAT sources opening angle between the jets is more than ninety degrees. We found that almost 80 per cent of our sources are associated with a known galaxy cluster. We mentioned various useful physical properties of these HT sources. Taking advantage of a large sample of newly discovered HT sources, various statistical studies have been done. The luminosity range of sources presented in the current paper is $10^{39}$ $leq$ $L_{1.4GHz}$ $leq$ $10^{43}$ erg sec$^{-1}$. We identified optical counterparts for 193 WAT and 104 NAT sources. The sources are found up to redshift 2.08.
We present results from a study of seven large known head-tail radio galaxies based on observations using the Giant Metrewave Radio Telescope at 240 and 610 MHz. These observations are used to study the radio morphologies and distribution of the spec
tral indices across the sources. The overall morphology of the radio tails of these sources is suggestive of random motions of the optical host around the cluster potential. The presence of the multiple bends an d wiggles in several head-tail sources is possibly due to the precessing radio jets. We find steepening of the spectral index along the radio tails. The prevailing equipartition magnetic field also decreases a long the radio tails of these sources. These steepening trends are attributed to the synchrotron aging of plasma toward the ends of the tails. The dynamical ages of these sample sources have been estimated to be ~100 Myr, which is a factor of six more than the age estimates from the radiative losses due to synchrotron cooling.
Aims. Narrow-angle tailed (NAT) sources in clusters of galaxies can show on the large scale very narrow tails that are unresolved even at arcsecond resolution. These sources could therefore be classified as one-sided jets. The aim of this paper is to
gain new insight into the structure of these sources, and establish whether they are genuine one-sided objects, or if they are two-sided sources. Methods. We observed a sample of apparently one-sided NAT sources at subarcsecond resolution to obtain detailed information on their structure in the nuclear regions of radio galaxies. Results. Most radio galaxies are found to show two-sided jets with sharp bends, and therefore the sources are similar to the more classical NATs, which are affected by strong projection effects.
The peculiar morphology of Head-Tail (HT) radio galaxies indicates strong interactions between the radio jets and their intra-cluster medium. We systematically search for HT radio galaxies from LOFAR Two-metre Sky Survey first data release (LoTSS DR1
) at 144 MHz frequency. We present here a catalogue of fifty new HT radio sources, among them, five are Narrow-Angle Tailed sources (NATs) and forty-five are Wide Angle Tailed sources (WATs). NATs are characterized by tails bent in a narrow V like shape with less than a ninety-degree opening angle. For WAT radio galaxies, the opening angle between jets is more than ninety degrees which exhibit wide C like morphologies. We found that thirty-one out of fifty HT sources are associated with known galaxy clusters. The various physical properties and statistical studies of these HT sources are also presented in this paper.
The amount and nature of the evolution of the X-ray properties of clusters of galaxies provides information on the formation of structure in the universe and on the properties of the universe itself. The cluster luminosity - temperature relation does
not evolve strongly, suggesting that the hot X-ray gas had a more complicated thermodynamic history than simply collapsing into the cluster potential well. Cluster X-ray luminosities do evolve. The dependence of this evolution on redshift and luminosity is characterized using two large high redshift samples. Cluster X-ray temperatures also evolve. This evolution constrains the dark matter and dark energy content of the universe as well as other parameters of cosmological interest.
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