VLBI observation of giant radio galaxy J1313+696 at 2.3/8.4 GHz

We report the result of VLBI observation of the giant radio galaxy J1313+696 (4C +69.15) at 2.3/8.4 GHz, only the core component of the giant radio galaxy was detected in the VLBI observation at the dual frequencies. The result shows a steep spectrum core with $\alpha=-0.82$ ($S \propto \nu^{\alpha}$) between 2.3 GHz and 8.4 GHz. The steep spectrum core may be a sign of renewed activity. Considering also the upper limit flux density of 2.0 mJy at 0.6 GHz from Konar et al. 2004 the core has a GHz-peaked spectrum, implying that the core is compact and absorbed. Further high resolution VLBI observations are needed to identify if the steep spectrum core is consisting of a core and steep spectrum jet.Comment: 3 pages, 3 figure

Time Domain Regional Discriminants

The time and frequency domains are equivalent displays of seismic trace, information, though some qualities of the signal are more easily observed in one domain than the other. The relative frequency excitation of Lg, for instance, is most easily viewed in the frequency domain, but such waveform qualities as the sequence in which pulses arrive in the wave train or the sharpness of pulse onset are most easily studied in the time domain (Murphy and Bennett, 1982, Blandford, 1981). Because of the tremendous complexity of high frequency regional data, most attempts at using it for discrimination purposes have involved analysis of the frequency content of the various arrivals either through transforming selected windows or through multiple bandpass filtering. We report here on our initial attempts to explore the alternative and to discriminate events using those waveform characteristics most easily observed in the time domain. A second advantage of time domain analysis approaches is that they permit a deeper insight into the physical processes creating a seismic signal's character. For this reason, they can be more e3silv used to evaluate the transportabilty of a discriminant to varying geophysical and tectonic regimes. This is an especially important feature in the development of regional discriminants. The most prominent and successful spectral regional discriminants have been empirically developed. This means that they must be redeveloped and reverified in each new area. As we shall show in the following, through rigorous time domain analysis such features as regional depth phases can be identified and used to discriminate. Discriminants based on such simple physical features as source depth should be transportable anywhere. In work recently completed under the treaty verification program, we have proved that such time domain discriminants do exist. In analyzing a test discrimination data set from the western U. S., we have discovered that the onset of P_n is always very similar for explosions and that few earthquakes have this unique waveform character. This information can be constructed into a simple discrimination scheme by testing the correlation of observed P_n waveform onsets with average waveforms observed from explosions. High correlations indicate explosions and low correlations earthquakes. We have also discovered that the regional phase P_g is actually composed of a sequence of sub-arrivals which correspond to successively higher orders of reverberation in the crust. In realistic crust models, the depth phases play an important role in the waveshapes of these sub-arrivals. By selecting an appropriate frequency band to analyze, we have been able to accurately model this type of data from explosions in the western United States. Over the very relevant regional distance ranges of 200 to 600 km, it appears that a discrimination procedure very similar to the one which is known to work for P_n will also be effective for P_g. We are investigating whether similar discriminants can be constructed based on the phases S_n and S_g in areas where those phases are prominent arrivals

Time Domain Regional Discriminants

The time and frequency domains are equivalent displays of seismic trace, information, though some qualities of the signal are more easily observed in one domain than the other. The relative frequency excitation of Lg, for instance, is most easily viewed in the frequency domain, but such waveform qualities as the sequence in which pulses arrive in the wave train or the sharpness of pulse onset are most easily studied in the time domain (Murphy and Bennett, 1982, Blandford, 1981). Because of the tremendous complexity of high frequency regional data, most attempts at using it for discrimination purposes have involved analysis of the frequency content of the various arrivals either through transforming selected windows or through multiple bandpass filtering. We report here on our initial attempts to explore the alternative and to discriminate events using those waveform characteristics most easily observed in the time domain. A second advantage of time domain analysis approaches is that they permit a deeper insight into the physical processes creating a seismic signal's character. For this reason, they can be more e3silv used to evaluate the transportabilty of a discriminant to varying geophysical and tectonic regimes. This is an especially important feature in the development of regional discriminants. The most prominent and successful spectral regional discriminants have been empirically developed. This means that they must be redeveloped and reverified in each new area. As we shall show in the following, through rigorous time domain analysis such features as regional depth phases can be identified and used to discriminate. Discriminants based on such simple physical features as source depth should be transportable anywhere. In work recently completed under the treaty verification program, we have proved that such time domain discriminants do exist. In analyzing a test discrimination data set from the western U. S., we have discovered that the onset of P_n is always very similar for explosions and that few earthquakes have this unique waveform character. This information can be constructed into a simple discrimination scheme by testing the correlation of observed P_n waveform onsets with average waveforms observed from explosions. High correlations indicate explosions and low correlations earthquakes. We have also discovered that the regional phase P_g is actually composed of a sequence of sub-arrivals which correspond to successively higher orders of reverberation in the crust. In realistic crust models, the depth phases play an important role in the waveshapes of these sub-arrivals. By selecting an appropriate frequency band to analyze, we have been able to accurately model this type of data from explosions in the western United States. Over the very relevant regional distance ranges of 200 to 600 km, it appears that a discrimination procedure very similar to the one which is known to work for P_n will also be effective for P_g. We are investigating whether similar discriminants can be constructed based on the phases S_n and S_g in areas where those phases are prominent arrivals

A survey of extended radio jets with Chandra and HST

We present the results from an X-ray and optical survey of a sample of 17 radio jets in AGN performed with Chandra and HST. The sample was selected from the radio and is unbiased toward detection at shorter wavelengths, but preferentially it includes beamed sources. We find that X-ray emission is common on kpc-scales, with over half radio jets exhibiting at least one X-ray knot on the Chandra images. The distributions of the radio-to-X-ray and radio-to-optical spectral indices for the detected jets are similar to the limits for the non-detections,suggesting all bright radio jets have X-ray counterparts which will be visible in longer observations. Comparing the radio and X-ray morphologies shows that the majority of the X-ray jets have structures that closely map the radio. Analysis of the SED of the jet knots suggest the knots in which the X-ray and radio morphologies track each other produce X-rays by IC scattering of the Cosmic Microwave Background. The remaining knots produce X-rays by the synchrotron process. Spectral changes are detected along the jets, with the ratio of the X-ray-to-radio and optical-to-radio flux densities decreasing from the inner to the outer regions. This suggests the presence of an additional contribution to the X-ray flux in the jet's inner part, either from synchrotron or IC of the stellar light. Alternatively, in a pure IC/CMB scenario, the plasma decelerates as it flows from the inner to the outer regions. Finally, the X-ray spectral indices for the brightest knots are flat, indicating that the bulk of the luminosity of the jets is emitted at GeV energies, and raising the interesting possibility of future detections with GLAST.Comment: 26 pages, 6 ps figures, 6 jpeg figures (1 replaced); accepted for publication in Ap

Intermittent jet activity in the radio galaxy 4C29.30?

We present radio observations at frequencies ranging from 240 to 8460 MHz of the radio galaxy 4C29.30 (J0840+2949) using the Giant Metrewave Radio Telescope (GMRT), the Very Large Array (VLA) and the Effelsberg telescope. We report the existence of weak extended emission with an angular size of $\sim$520 arcsec (639 kpc) within which a compact edge-brightened double-lobed source with a size of 29 arcsec (36 kpc) is embedded. We determine the spectrum of the inner double from 240 to 8460 MHz and show that it has a single power-law spectrum with a spectral index of $\sim$0.8. Its spectral age is estimated to be \lapp33 Myr. The extended diffuse emission has a steep spectrum with a spectral index of $\sim$1.3 and a break frequency \lapp240 MHz. The spectral age is \gapp200 Myr, suggesting that the extended diffuse emission is due to an earlier cycle of activity. We reanalyse archival x-ray data from Chandra and suggest that the x-ray emission from the hotspots consists of a mixture of nonthermal and thermal components, the latter being possibly due to gas which is shock heated by the jets from the host galaxy.Comment: 14 pages, 11 figures, accepted for publication in MNRA

Search and analysis of giant radio galaxies with associated nuclei (SAGAN) -- I : New sample and multi-wavelength studies

We present the first results of a project called SAGAN, which is dedicated solely to the studies of relatively rare megaparsec-scale radio galaxies in the Universe, called giant radio galaxies (GRGs). We have identified 162 new GRGs primarily from the NVSS with sizes ranging from ~0.71 Mpc to 2.82 Mpc in the redshift range of ~0.03 - 0.95, of which 23 are hosted by quasars (giant radio quasars, GRQs). As part of the project SAGAN, we have created a database of all known GRGs, the GRG catalogue, from the literature (including our new sample); it includes 820 sources. For the first time, we present the multi-wavelength properties of the largest sample of GRGs. Our results establish that the distributions of the radio spectral index and the black hole mass of GRGs do not differ from the corresponding distributions of normal-sized radio galaxies (RGs). However, GRGs have a lower Eddington ratio (ER) than RGs. Using the mid-infrared data, we classified GRGs in terms of their accretion mode: either a high-power radiatively efficient high-excitation state, or a radiatively inefficient low-excitation state. We find that GRGs in high-excitation state statistically have larger sizes, stronger radio power, jet kinetic power, and higher ER than those in low-excitation state. Our analysis reveals a strong correlation between the ER and the scaled jet kinetic power, which suggests a disc-jet coupling. Our environmental study reveals that ~10% of all GRGs may reside at the centres of galaxy clusters, in a denser galactic environment, while the majority appears to reside in a sparse environment. We find that the probability of BCG as a GRG is quite low. We present new results for GRGs that range from black hole mass to large-scale environment properties. We discuss their formation and growth scenarios, highlighting the key physical factors that cause them to reach their gigantic size. Abridged.Comment: Accepted for publication in Astronomy & Astrophysics. 14 figures, 7 tables and 7 montages. Comments are welcome. "SAGAN Project website https://sites.google.com/site/anantasakyatta/sagan

Electrolyte (Na, K, Cl, Ca, Pi and Mg) profile of Zovawk pigs of Mizoram, India in different age groups

A study was carried out to find out the electrolyte profile of different age groups of an indigenous pig locally called Zovawk of Mizoram, India. The plasma Na and Cl were not influenced by age. The plasma concentration of Na was found to be in higher ranges while that of K was in lower range. Adult pigs had higher K (

On the Evolution of and High-Energy Emission from GHz-Peaked-Spectrum Sources

Here we discuss evolution and broad-band emission of compact (< kpc) lobes in young radio sources. We propose a simple dynamical description for these objects, consisting of a relativistic jet propagating into a uniform gaseous medium in the central parts of an elliptical host. In the framework of the proposed model, we follow the evolution of ultrarelativistic electrons injected from a terminal hotspot of a jet to expanding lobes, taking into account their adiabatic energy losses as well as radiative cooling. This allows us to discuss the broad-band lobe emission of young radio sources. In particular, we argue that the observed spectral turnover in the radio synchrotron spectra of these objects cannot originate from the synchrotron self-absorption process but is most likely due to free-free absorption effects connected with neutral clouds of interstellar medium engulfed by the expanding lobes and photoionized by active centers. We also find a relatively strong and complex high-energy emission component produced by inverse-Compton up-scattering of various surrounding photon fields by the lobes' electrons. We argue that such high energy radiation is strong enough to account for several observed properties of GHz-peaked-spectrum (GPS) radio galaxies at UV and X-ray frequencies. In addition, this emission is expected to extend up to GeV (or possibly even TeV) photon energies and can thus be probed by several modern gamma-ray instruments. In particular, we suggest that GPS radio galaxies should constitute a relatively numerous class of extragalactic sources detected by GLAST.Comment: 32 pages, 3 figures included. Revised version, accepted for publication in Ap

Evidence for low power radio jet-ISM interaction at 10 parsec in the dwarf AGN host NGC 4395

Black hole driven outflows in galaxies hosting active galactic nuclei (AGN) may interact with their interstellar medium (ISM) affecting star formation. Such feedback processes, reminiscent of those seen in massive galaxies, have been reported recently in some dwarf galaxies. However, such studies have usually been on kiloparsec and larger scales and our knowledge on the smallest spatial scales to which these feedback processes can operate is unclear. Here we demonstrate radio jet$-$ISM interaction on the scale of an asymmetric triple radio structure of $\sim$ 10 parsec size in NGC 4395. This triple radio structure is seen in the 15 GHz continuum image and the two asymmetric jet-like structures are situated on either side of the radio core that coincides with the optical {\it Gaia} position. The high resolution radio image and the extended [OIII]$\lambda$5007 emission, indicative of an outflow, are spatially coincident and are consistent with the interpretation of a low power radio jet interacting with the ISM. Modelling of the spectral lines using {\tt MAPPINGS}, and estimation of temperature using optical integral field spectroscopic data suggest shock ionization of the gas. The continuum emission at 237 GHz, though weak, was found to spatially coincide with the AGN. However, the CO(2$-$1) line emission was found to be displaced by around 20 parsec northward of the AGN core. The spatial coincidence of molecular H$_2$$\lambda$2.4085 along the jet direction, the morphology of ionised [OIII]$\lambda$5007 and displacement of the CO(2$-$1) emission argues for conditions less favourable for star formation in the central $\sim$ 10 parsec region.Comment: 20 pages, 18 figures, accepted for the publication of The Astrophysical Journa

Observational Evidence of Accretion Disk-Caused Jet Precession in Galactic Nuclei

We show that the observational data of extragalactic radio sources tend to support the theoretical relationship between the jet precession period and the optical luminosity of the sources, as predicted by the model in which an accretion disk causes the central black hole to precess.Comment: 13 pages, 1 figure, accepted for publication in ApJ Letter