B2114+022: a distant radio source gravitationally lensed by a starburst galaxy (original) (raw)
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J1420−0545: The Radio Galaxy Larger than 3C 236
The Astrophysical Journal, 2008
We report the discovery of the largest giant radio galaxy, J1420-0545: a FR type II radio source with an angular size of 17.4' identified with an optical galaxy at z=0.3067. Thus, the projected linear size of the radio structure is 4.69 Mpc (if we assume that H 0 =71 km s −1 Mpc −1 , Ω m =0.27, and Ω Λ =0.73). This makes it larger than 3C236, which is the largest double radio source known to date. New radio observations with the 100 m Effelsberg telescope and the Giant Metrewave Radio Telescope, as well as optical identification with a host galaxy and its optical spectroscopy with the William Herschel Telescope are reported. The spectrum of J1420−0545 is typical of elliptical galaxies in which continuum emission with the characteristic 4000Å discontinuity and the H and K absorption lines are dominated by evolved stars. The dynamical age of the source, its jets' power, the energy density, and the equipartition magnetic field are calculated and compared with the corresponding parameters of other giant and normal-sized radio galaxies from a comparison sample. The source is characterized by the exceptionally low density of the surrounding IGM and an unexpectedly high expansion speed of the source along the jet axis. All of these may suggest a large inhomogeneity of the IGM.
RC J1148+ 0455 identification: gravitational lens or group of galaxies?
2000
The structure of the radio source RC B1146+052 of the "Cold"catalogue is investigated by data of the MIT-GB-VLA survey at 4850 MHz. This source belongs to the steep spectrum radio sources subsample of the RC catalogue. Its spectral index is α =-1.04. The optical image of this source obtained with 6m telescope is analysed. The possible explanations of the complex structure of radio components are considered.
A Study of 13 Powerful Classical Double Radio Galaxies
The Astrophysical Journal Supplement Series, 2008
We have carried out an extensive study of a sample of 13 large, powerful Fanaroff-Riley type II radio galaxies with the Very Large Array in multiple configurations at 330 MHz, 1.4, 5 and 8 GHz. We present the total intensity, polarization, spectral index, and rotation measure maps of the sources. On the whole the 13 FRII sources have symmetric structures with arm-length ratios close to unity, small misalignment angles and low values of radio core prominence, suggesting that these radio galaxies lie close to the plane of the sky. We have revisited some well known radio galaxy correlations using a large combined dataset comprising our radio galaxies and others from the literature. We confirm that the hotspot size correlates with the core-hotspot distance. The hotspot spectral index is correlated with, and flatter than the lobe spectral index, consistent with the assumptions of spectral aging models. Both the hotspot and lobe spectral index are correlated with redshift. The depolarization asymmetry in the lobes is not correlated with the radio core prominence or misalignment angle, which are statistical indicators of orientation. The 'Liu-Pooley' correlation of lobe depolarization with the lobe spectral index is significant in our radio galaxy To this end, we observed 13 FRII radio galaxies with the Very Large Array (VLA) in multiple configurations at 330 MHz, 1.4 GHz, 5 GHz, and 8 GHz. Here we present images of the total and polarized radio intensity, spectral index between 1.4 and 5 GHz, 0.3 and 1.4 GHz, and rotation measure between 1.4 and 5 GHz 1 . Further, we probe the relationship between different global characteristics of the radio galaxies by augmenting our data with additional galaxy data gleaned from the literature. We will subsequently refer to this extended, eclectic sample as the "combined" dataset, while the 13 FRII galaxies will be referred to as such.
2010
RC J0311+0507, the parent galaxy of which has a redshift, z, of 4.514, is one of the most luminous objects in the High-z radio Universe. New MERLIN and EVN intensity and polarization maps of the object at 1.7 GHz and 5 GHz show multiple compact components and extended emission orientated in a primarily NS direction on either side of what appears to be a core. The flux density ratio between the southern and northern components is highly asymmetric, with values of ∼30 at 5 GHz and ∼10 at 1.7 GHz. New optical observations using the Russian 6-m optical telescope confirm the identification of the radio source with a galaxy, and show the presence of extended Ly α emission. The very high radio luminosities and the high "bulge optical emission" suggest the presence of a very massive (10 9 M ⊙ ) Black Hole (BH). Assuming that the age of the Universe at z = 4.514 is only ∼1.3 Gyr and that the standard epoch for the formation of galaxies is within the redshift range from 7 to 10, there is less than 0.5 Gyr available for the formation of RC J0311+0507. The quick growth of a BH mass solely as a result of a merger is questionable, and the simple evolution from several solar masses to 10 9 M ⊙ in a timescale of less 1 Gyr appears to be very improbable.
Revealing the unusual structure of the KAT-7-discovered giant radio galaxy J0133−1302
Monthly Notices of the Royal Astronomical Society, 2021
We present a new study of the 1.7 Mpc KAT-7-discovered giant radio galaxy, J0133−1302, which was carried out using GMRT data at 323 and 608 MHz. This source is located at RA 01h33m13s and Dec −13○03′00″ and has a photometric redshift of ∼0.3. We discovered unusual morphological properties of the source which include lobes that are exceptionally asymmetric, where the upper lobe is much further from the core when compared to the lower lobe, and a complex structure of the upper lobe. The complex structure of the upper lobe hints at the presence of another source, in close proximity to the edge of the lobe, which resembles a bent-double, or distorted bent tail (DBT) radio galaxy. Both the upper lobe and the lower lobe have a steep spectrum, and the synchrotron age of the lower lobe should be less than about 44 Myr. The core has an inverted spectrum, and our results suggest that the parent galaxy in J0133−1302 is starting a new jet activity. Our spectral analysis indicates that this sour...
Origin of X-shaped radio-sources: further insights from the properties of their host galaxies
We analyze the properties of a sample of X-shaped radio-sources (XRSs). These objects show, in addition to the main lobes, a pair of wings that produce their peculiar radio morphology. We obtain our sample by selecting from the initial list of Cheung (2007, AJ, 133, 2097) the 53 galaxies with the better defined wings and with available SDSS images. We identify the host galaxies and measure their optical position angle, obtaining a positive result in 22 cases. The orientation of the secondary radio structures shows a strong connection with the optical axis, with all (but one) wing forming an angle larger than 40 • with the host major axis. The probability that this is compatible with a uniform distribution is P = 0.9 × 10 −4. For all but three sources of the sample, spectroscopic or photometric redshifts are avaliable. The radio luminosity distribution of XRSs has a high power cutoff at L ∼ 10 34 erg s −1 Hz −1 at 1.4 GHz. Spectra are available from the SDSS for 28 XRSs. We modeled them to extract information on their emission lines and stellar population properties. The sample is formed by approximately the same number of high and low excitation galaxies (HEGs and LEGs); this classification is essential for a proper comparison with non-winged radio-galaxies. XRSs follow the same relations between radio and line luminosity defined by radio-galaxies in the 3C sample. While in HEGs a young stellar population is often present, this is not detected in the 13 LEGs, which is, again, in agreement with the properties of non-XRSs. The lack of young stars in LEGs supports the idea that they have not experienced a recent gas-rich merger. The connection between the optical axis and the wing orientation, as well as the stellar population and emission-line properties, provide further support for a hydro-dynamic origin of the radio-wings (for example, associated with the expansion of the radio cocoon in an asymmetric external medium) rather than with a change of orientation of the jet axis. In this framework, the high luminosity limit of XRSs can be interpreted as being due to high power jets being less affected by the properties of the surrounding medium.
The most distant radio galaxies
Advances in Space Research, 1991
High redshift radio galaxies (z > 1) are unique spatially extended probes of the galactic environment at the earliest observed epochs. Recent discoveries have unleashed a host of questions about their nature. Many new objects are being found, and their unusual properties are being uncovered. They generally exhibit the "alignment effect" wherein their highly elongated lumpy morphologies are lined up along the axes of their powerful radio sources. Evidence for both large star formation rates and scattered quasar light are found in the aligned continuum. ALIGNED RADIO GALAXIES The field of high redshift radio galaxies has undergone a revolution in the last three years. In the early eighties, high redshift (1 < z < 2) radio galaxies were viewed as natural extentions of their low redshift counterpartsgenerally rather normal giant ellipticals. This of course made them attractive objects for studies of galaxy evolution and ultimately, it was hoped, for use in distinquishing between cosmological world models. With the near complete identification of the 3CR catalog by Spinrad /1/ and collaborators, it was possible to begin a number of detailed studies of the properties of thes objects. Lilly and Longair /2/ obtained infrared measurments of the 3CR galaxies, and this infrared data along with optical data obtained by the Berkely group was investigated with the newly developed Bruzual models /3/. The limitations of these models (coeval galaxy formation, oversimplified treatment of AGB stars, simple assumptions for unknowns such as the IMF, the star formation rate etc.) were appreciated but the ability of the models to fit the data gave hope that these objects were probin.g normal galaxy evolution. However, in the late eighties a series of new discoveries and new ideas have forced us to recognize these objects as having extraordinary properties which are not understood. The first of these was the discovery by Chambers ei al. /4/ and McCarthy ei al. /5/ of the "alignment effect", the curious fact that at high redshift, (and only at high redshift) radio galaxies often have highly elongated optical continuum morphologies, and these optical extensions are reasonably well lined up with the axis of the powerful radio source. At about the same time the long standing "z = 2" barrier for radio galaxies was broken with the discovery of 4C40.36 at z = 2.267 by Chambers, Miley and van Breguel /6/ using a new technique of selecting candidates by their ultra steep radio spectrum. Lilly /7/ then made the discovery of the "1 Jy" source B2 0902+34 at z = 3.4. At present the redshift record rests with one of the ultra steep spectrum sources, 4C41.17 at z = 3.8, found by Chambers, Miley, and van Bruegel /8/. However, several groups are now pursing various samples and the number of known z> 1 galaxies is rapidily increasing. With the discovery of 4C41.17 and 0902+34 the infrared K band Hubble diagram has now been extended out to very high redshifts /9/. However, the development and availability of infrared arrays led to the discovery by Chambers et al. /10/ and Eisenhardt and Chokshi (2)235 (2)236 K. C. Chambers
J1343+3758: the third largest FRII-type radio galaxy in the Universe
Astronomy & Astrophysics - ASTRON ASTROPHYS, 2000
A radio source of the Fanaroff-Riley type II with the angular size of 11.3 arc min is identified with an optical galaxy at z=0.229. Thus, the projected linear extent of the radio structure is 3.14 Mpc which makes it the third largest classical double radio source known after 3C236 and WNB2147+816. The high-frequency VLA observations, a galaxy identification and its optical spectroscopy are reported. The equipartition magnetic field and energy density in the source is calculated and compared with corresponding parameters of other giants known, indicating that either parameter of the source investigated is extremely low. On the other hand, the age estimate of relativistic electrons and the advance speed of the lobe material are comparable to the respective parameters characterizing other low-luminosity giant sources, as well as much smaller and brighter 3CR sources. The environment analysis suggests that J1343+3758 lies in a significantly poor region of intergalactic medium.
IGR J17488–2338: a newly discovered giant radio galaxy
Astronomy & Astrophysics, 2014
We present the discovery of a large scale radio structure associated with IGR J17488-2338, a source recently discovered by INTEGRAL and optically identified as a broad line AGN at redshift 0.24. At low frequencies, the source properties are those of an intermediate-power FR II radio galaxy with a linear size of 1.4 Mpc. This new active galaxy is therefore a member of a class of objects called Giant Radio Galaxies (GRGs), a rare type of radio galaxies with physical sizes larger than 0.7 Mpc; they represent the largest and most energetic single entities in the Universe and are useful laboratories for many astrophysical studies. Their large scale structures could be due either to special external conditions or to uncommon internal properties of the source central engine The AGN at the centre of IGR J17488-2338 has a black hole of 1.3×10 9 solar masses, a bolometric luminosity of 7×10 46 erg s −1 and an Eddington ratio of 0.3, suggesting that it is powerful enough to produce the large structure observed in radio. The source is remarkable also for other properties, among which its X-ray absorption, at odds with its type 1 classification, and the presence of a strong iron line which is a feature not often observed in radio galaxies.
A new sample of large angular size radio galaxies
Astronomy and Astrophysics, 2004
We present in this paper a detailed study of a new sample of large angular size FR I and FR II radio galaxies and compare the properties of the two classes. As expected, a pure morphology based distinction of FR Is and FR IIs corresponds to a break in total radio power. The radio cores in FR Is are also weaker than in FR IIs, although there is not a well defined break power. We find that asymmetry in the structure of the sample members must be the consequence of anisotropies in the medium where the lobes expand, with orientation playing a minor role. Moreover, literature data and our observations at kiloparsec scales suggest that the large differences between the structures of FR I and FR II radio galaxies must arise from the poorly known central kiloparsec region of their host galaxies. We analyze the sub-sample of giant radio galaxies, and do not find evidence that these large objects require higher core powers. Our results are consistent with giant radio galaxies being the older population of normal FR I and FR II objects evolving in low density environments. Comparing results from our sample with predictions from the radio luminosity function we find no evidence of a possible FR II to FR I evolution. Moreover, we conclude that at z ∼ 0.1, one out of four FR II radio sources has a linear size above 500 kpc, thus being in an advanced stage of evolution (for example, older than ∼ 10 Myr assuming a jet-head velocity of 0.1c). Radio activity seems to be a short-lived process in active galaxies, although in some cases recurrent: five objects in our sample present signs of reactivation in their radio structures.