X-ray Lobes Research Articles

Jets of SS 433 on scales of dozens of parsecs

The radio nebula W50 harbours the relativistic binary system SS433, which is a source of the powerful wind and jets. The origin of W50 is wrapped in the interplay of the wind, supernova remnant and jets. The evolution of the jets on the scales of the nebula is a Rosetta stone for its origin. To disentangle the roles of these components, we study physical conditions of the jets propagation inside W50, and determine deceleration of the jets. The morphology and parameters of the interior of W50 are analyzed using the available observations of the eastern X-ray lobe, which traces the jet. In order to estimate deceleration of this jet, we devised a simplistic model of the viscous interaction, via turbulence, of a jet with the ambient medium, which would fit mass entrainment from the ambient medium into the jets of the radio galaxy 3C31, the well studied case of continuously decelerating jets. X-ray observations suggest that the eastern jet persists through W50 as hollow one, and is recollimated to the opening $\sim 30^\circ$. From the thermal emission of the eastern X-ray lobe, we determine a pressure of $P \sim 3\cdot 10^{-11}$ erg/cm$^3$ inside W50. In the frame of a theory of the dynamics of radiative supernova remnants and stellar wind bubbles, this pressure in combination with other known parameters restricts W50's origin to a supernova happened $\sim 100\,000$ yr ago. Also, this pressure in our entrainment model gives a deceleration of the jet by $\sim 60\%$ in the bounds of W50's spherical component, of radius $\sim 40$ pc. In this case, the age of the jet should be $\ll 27\,000$ yr so as to satisfy the sphericity of W50. The entrainment model comes to the viscous stress in a jet of a form $\sigma = \alpha P$, where the viscosity parameter $\alpha$ is predefined by the model.

CMB-induced radio quenching of high-redshift jetted AGNs with highly magnetic hotspots

In an effort to understand the cause of the apparent depletion in the number density of radio-loud AGNs at $z>3$, this work investigates the viability of the so-called Cosmic Microwave Background (CMB) quenching mechanism of intrinsically jetted, high-z AGNs, whereby Inverse Compton scattering of CMB photons off electrons within the extended lobes results in a substantial dimming of the lobe synchrotron emission at GHz frequencies, while simultaneously boosting their diffuse X-ray signal. We focus on five $z>3.5$ radio galaxies that have sufficiently deep Chandra exposure (> 50 ks) to warrant a meaningful investigation of any extended X-ray emission. For those objects with evidence for statistically significant extended X-ray lobes (4C 41.17 and 4C 03.24), we combine the Chandra measurements with literature data at lower frequencies to assemble the systems' Spectral Energy Distributions (SEDs), and utilize state-of-the-art SED modelling (Ghisellini et al. 2015) -- including emission from the disk, torus, jet, hotspots, and lobes -- to infer their physical parameters. For both radio galaxies, the magnetic energy density in the hotspots is found to exceed the energy density in CMB photons, wheres the opposite is true for the lobes. This implies that any extended synchrotron emission likely originates from the hotspots themselves, rather than the lobes. Conversely, Inverse Compton scattering of CMB photons dominates the extended X-ray emission from the lobes, which are effectively "radio-quenched". As a result, CMB quenching is effective in these systems in spite of the fact that the observed X-ray to radio luminosity ratio does not bear the signature $(1+z)^4$ dependence of the CMB energy density.

A NEW PERSPECTIVE OF THE RADIO BRIGHT ZONE AT THE GALACTIC CENTER: FEEDBACK FROM NUCLEAR ACTIVITIES

ABSTRACT New observations of Sgr A have been carried out with the Jansky VLA in the B and C arrays using the broadband (2 GHz) continuum mode at 5.5 GHz. The field of view covers the central 13′ (30 pc) region of the radio-bright zone at the Galactic center. Using the multi-scale and multi-frequency-synthesis (MS-MFS) algorithms in CASA, we have imaged Sgr A with a resolution of 1″, achieving an rms noise of 8 μJy beam−1, and a dynamic range of 100,000:1. Both previously known and newly identified radio features in this region are revealed, including numerous filamentary sources. The radio continuum image is compared with Chandra X-ray images, with a CN emission-line image obtained with the Submillimeter Array and with detailed Paschen-α images obtained with Hubble Space Telescope/NICMOS. We discuss several prominent features in the radio image. The “Sgr A west Wings” extend 2′ (5 pc) from the NW and SE tips of the Sgr A west H ii region (the “Mini-spiral”) to positions located 2.9 and 2.4 arcmin to the northwest and southeast of Sgr A*, respectively. The NW wing, along with several other prominent features, including the previously identified “NW Streamers,” form an elongated radio lobe (NW lobe), oriented nearly perpendicular to the Galactic plane. This radio lobe, with a size of 6.′3 × 3.′2 (14.4 pc × 7.3 pc), has a known X-ray counterpart. In the outer region of the NW lobe, a row of three thermally emitting rings is observed. A field containing numerous amorphous radio blobs extends for a distance of ∼2 arcmin beyond the tip of the SE wing; these newly recognized features coincide with the SE X-ray lobe. Most of the amorphous radio blobs in the NW and SE lobes have Paschen-α counterparts. We propose that they have been produced by shock interaction of ambient gas concentrations with a collimated nuclear wind or an outflow that originated from within the circumnuclear disk (CND). We also discuss the possibility that the ionized wind or outflow has been launched by radiation force produced by the central star cluster. Finally, we remark on the detailed structure of a prominent radio emission feature located within the shell of the Sgr A east supernova remnant. Because this feature—the “Sigma Front”—correlates well in shape and orientation with the nearby edge of the CND, we propose that it is a reflected shock wave resulting from the impact of the Sgr A east blast wave on the CND.

Do high-redshift quasars have powerful jets?

Abstract Double-lobed radio galaxies a few hundreds of kpc in extent, like Cygnus A, are common at redshifts of 1–2, arising from some 10 per cent of the most powerful active galactic nuclei (AGN). At higher redshifts, they are rare, with none larger than a few tens of kpc known above redshift z ∼ 4. Recent studies of the redshift evolution of powerful jetted objects indicate that they may constitute a larger fraction of the AGN population above redshift 2 than that appears from a simple consideration of detected GHz radio sources. The radio band is misleading as the dramatic (1 + z)4 boost in the energy density of the cosmic microwave background (CMB) causes inverse Compton scattering to dominate the energy losses of relativistic electrons in the extended lobes produced by jets, making them strong X-ray, rather than radio, sources. Here, we investigate limits to X-ray lobes around two distant quasars, ULAS J112001.48+064124.3 at z = 7.1 and SDSS J1030+0524 at z = 6.3, and find that powerful jets could be operating yet be currently undetectable. Jets may be instrumental in the rapid build-up of billion M⊙ black hole at a rate that violates the Eddington limit.

A new perspective on the radio active zone at the Galactic center – feedback from nuclear activities

AbstractBased on our deep image of Sgr A using broadband data observed with the VLA† at 6 cm, we present a new perspective of the radio bright zone at the Galactic center. We further show the radio detection of the X-ray Cannonball, a candidate neutron star associated with the Galactic center SNR Sgr A East. The radio image is compared with the Chandra X-ray image to show the detailed structure of the radio counterparts of the bipolar X-ray lobes. The bipolar lobes are likely produced by the winds from the activities within Sgr A West, which could be collimated by the inertia of gas in the CND, or by the momentum driving of Sgr A*; and the poloidal magnetic fields likely play an important role in the collimation. The less-collimated SE lobe, in comparison to the NW one, is perhaps due to the fact that the Sgr A East SN might have locally reconfigured the magnetic field toward negative galactic latitudes. In agreement with the X-ray observations, the time-scale of ∼1 × 104 yr estimated for the outermost radio ring appears to be comparable to the inferred age of the Sgr A East SNR.

ON THE RADIO POLARIZATION SIGNATURE OF EFFICIENT AND INEFFICIENT PARTICLE ACCELERATION IN SUPERNOVA REMNANT SN 1006

We present a radio polarization study of SN 1006, based on combined VLA and ATCA observations at 20 cm that resulted in sensitive images with an angular resolution of 10 arcsec. The fractional polarization in the two bright radio and X-ray lobes of the SNR is measured to be 0.17, while in the southeastern sector, where the radio and non-thermal X-ray emission are much weaker, the polarization fraction reaches a value of 0.6 +- 0.2, close to the theoretical limit of 0.7. We interpret this result as evidence of a disordered, turbulent magnetic field in the lobes, where particle acceleration is believed to be efficient, and a highly ordered field in the southeast, where the acceleration efficiency has been shown to be very low. Utilizing the frequency coverage of our observations, an average rotation measure of ~12 rad/m2 is determined from the combined data set, which is then used to obtain the intrinsic direction of the magnetic field vectors. While the orientation of magnetic field vectors across the SNR shell appear radial, a large fraction of the magnetic vectors lie parallel to the Galactic Plane. Along the highly polarized southeastern rim, the field is aligned tangent to the shock, and therefore also nearly parallel to the Galactic Plane. These results strongly suggest that the ambient field surrounding SN 1006 is aligned with this direction (i.e., from northeast to southwest) and that the bright lobes are due to a polar cap geometry. Our study establishes that the most efficient particle acceleration and generation of magnetic turbulence in SN 1006 is attained for shocks in which the magnetic field direction and shock normal are quasi-parallel, while inefficient acceleration and little to no generation of magnetic turbulence obtains for the quasi-perpendicular case.

Search for VHE gamma rays from SS433/W50 with the CANGAROO-II telescope

SS433, located at the center of the supernova remnant W50, is a close proximity binary system consisting of a compact star and a normal star. Jets of material are directed outwards from the vicinity of the compact star symmetrically to the east and west. Non-thermal hard X-ray emission is detected from lobes lying on both sides. Shock accelerated electrons are expected to generate VHE gamma rays through the inverse-Compton process in the lobes. Observations of the western X-ray lobe region of SS433/W50 system have been performed to detect VHE gamma rays using the 10 m CANGAROO-II telescope in August and September, 2001, and July and September, 2002. The total observation times are 85.2 h for ON source, and 80.8 h for OFF source data. No significant excess of VHE gamma rays has been found at three regions of the western X-ray lobe of SS433/W50 system. We have derived 99% confidence level upper limits to the fluxes of gamma rays and have set constraints on the strengths of the magnetic fields assuming the synchrotron/inverse-Compton model for the wide energy range of photon spectrum from radio to TeV. The derived lower limits are 4.3 μ G for the center of the brightest X-ray emission region and 6.3 μ G for the far end from SS433 in the western X-ray lobe. In addition, we suggest that the spot-like X-ray emission may provide a major contribution to the hardest X-ray spectrum in the lobe.

Outer Jet X‐Ray and Radio Emission in R Aquarii: 1999.8 to 2004.0

Chandra and VLA observations of the symbiotic star R Aqr in 2004 reveal significant changes over the 3-4 year interval between these observations and previous observations taken in with the VLA in 1999 and with Chandra in 2000. This paper reports on the evolution of the outer thermal X-ray lobe jets and radio jets. The emission from the outer X-ray lobe jets lies farther away from the central binary than the outer radio jets and comes from material interpreted as being shock-heated to ≃106 K, a likely result of collision between high-speed material ejected from the central binary and regions of enhanced gas density. Between 2000 and 2004, the northeast (NE) outer X-ray lobe jet moved out, away from the central binary, with an apparent projected motion of ≃580 km s-1. The southwest (SW) outer X-ray lobe jet almost disappeared between 2000 and 2004, presumably due to adiabatic expansion and cooling. The NE radio-bright spot also moved away from the central binary between 2000 and 2004, but with a smaller apparent velocity than the NE X-ray-bright spot. The SW outer lobe jet was not detected in the radio in either 1999 or 2004. The density and mass of the X-ray-emitting material is estimated. Cooling times, shock speeds, pressure, and confinement are discussed.

Evidence for Shocked Molecular Gas in the Galactic Supernova Remnant CTB 109 (G109.1-1.0)

We report the detection of molecular clouds around the X-ray-bright interior feature in the Galactic supernova remnant (SNR) CTB 109 (G109.1-1.0). This feature, called the lobe, has been previously suggested to be the result of an interaction of the SNR shock wave with a molecular cloud complex. We present new high-resolution X-ray data from the Chandra X-Ray Observatory and new high-resolution CO data from the Five College Radio Astronomy Observatory that show the region of interaction with the cloud complex in greater detail. The CO data reveal three clouds around the lobe in the velocity interval -57 km s-1 < v < -52 km s-1. The velocity profiles of 12CO in various parts of the east cloud are well fit with a Gaussian; however, at the position at which the CO cloud and the lobe overlap, the velocity profile has an additional component toward higher negative velocities. The molecular hydrogen density in this part of the cloud is relatively high (N ≈ 1.9 × 1020 cm-2), whereas the foreground absorption in X-rays (NH ≈ 4.5 × 1021 cm-2), obtained from Chandra data, is lower than in other parts of the cloud and in the north and south clouds. These results indicate that the east cloud has been hit by the SNR blast wave on the western side, forming the bright X-ray lobe.

The Chandra view of extended X-ray emission from Pictor A

We discuss the extended X-ray emission seen in three archival Chandraobservations, and one archival XMM-Newtonobservation, of the FRII radio galaxy Pictor A. The overall properties of the X-ray lobes are consistent with the conclusions of earlier workers that the extended X-ray emission is largely due to the inverse-Compton process, and the implied departure from equipartition is in the range seen by us in other sources. In d etail, we show that the X-ray/radio flux ratio varies quite strongly as a function of position thr oughout the source, and we discuss possible implications of this observation for the spatial v ariation of electron energy spectra and magnetic field strength through the lobe. We show that the rad io and X-ray properties of the lobe are not consistent with a simple model in which variations in the magnetic field strength alone are responsible for the observed differences between emission at different frequencies. We also discuss the origins of the extended emission seen around the eastern hotspot, arguing that it may be diffuse synchrotron radiation tracing a regio n of distributed particle acceleration, and the implications of a possible weak X-ray counterjet detection which, taken together with the other properties of the bright X-ray jet, leads us to suggest that the X-ray jet and possible counterjet are also produced by synchrotron emission.

Galaxy populations of double cluster RX J1053.7+5735 at z = 1.13

We present a study of the galaxy population in the cluster RX J1053.7+5735, one of the most distant X-ray selected clusters of galaxies and one which also shows an unusual double-lobed X-ray morphology, indicative of a possible equal-mass cluster merger. The cluster was discovered during the ROSAT deep pointings in the direction of the Lockman Hole. Using Keck-DEIMOS spectroscopic observations of galaxies in the 20 15 region surrounding RX J1053.7+5735, we secured redshifts for six galaxies in the range , with a mean redshift . This mean redshift agrees well with the cluster X-ray redshift previously estimated from the cluster X-ray Fe-K line, confirming the presence of a cluster at . Galaxies with concordant redshifts are located in both eastern and western sub-clusters of the double cluster structure, which indicates that both sub-clusters are at similar redshifts. This result is also consistent with a previous claim that both eastern and western X-ray lobes have similar X-ray redshifts. Based on their separation of ~250 kpc, these results support the interpretation that RX J1053.7+5735 is an equal-mass cluster merger taken place at , although further direct evidence for a dynamical state of the cluster is needed to make a more definitive statement about the cluster merging state. The six galaxies have a line-of-sight velocity dispersion ~ 650 km s-1, and all six show clear absorption features of CaII H and K and several Balmer lines that are typical of early galaxies at the present epoch, in agreement with their colors. A color–magnitude diagram, constructed from deep optical/NIR observations of the RX J1053.7+5735 field, shows a clear red color sequence. There is an indication that the red sequence in RX J1053.7+5735 lies ~0.3 to the blue of the Coma line, qualitatively consistent with previous studies investigating other clusters at .

A multi-wavelength study of the western lobe of W50 powered by the galactic microquasar SS 433

W50 remains the only supernova remnant (SNR) confirmed to harbor a microquasar: the powerful enigmatic source SS 433. Our past study of this fascinating SNR revealed two X-ray lobes distorting the radio shell as well as non-thermal X-rays at the site of interaction between the SS 433 eastern jet and the eastern lobe of W50. In this paper we present the results of a 75 ks Chandra ACIS-I observation of the peak of W50-west targeted to: (1) determine the nature of the X-ray emission and (2) correlate the X-ray emission with that in the radio and infrared domains. We have confirmed that at the site of interaction between the western jet of SS 433 and dense interstellar gas the X-ray emission is non-thermal in nature. The helical pattern observed in radio is also seen with Chandra. No correlation was found between the infrared and X-ray emission.

ChandraObservations of Extended X‐Ray Emission in Arp 220

We resolve the extended X-ray emission from the prototypical ultraluminous infrared galaxy Arp 220. Extended, faint edge-brightened, soft X-ray lobes outside the optical galaxy are observed to a distance of 10 to 15 kpc on each side of the nuclear region. Bright plumes inside the optical isophotes coincide with the optical line emission and extend 11 kpc from end to end across the nucleus. The data for the plumes cannot be fit by a single temperature plasma, and display a range of temperatures from 0.2 to 1 keV. The plumes emerge from bright, diffuse circumnuclear emission in the inner 3 kpc centered on the Halpha peak, which is displaced from the radio nuclei. There is a close morphological correspondence between the Halpha and soft X-ray emission on all spatial scales. We interpret the plumes as a starburst-driven superwind, and discuss two interpretations of the emission from the lobes in the context of simulations of the merger dynamics of Arp 220.

The ROSAT deep survey

The eastern lobe of the unusual double-lobed extended X-ray source RX J105343+5735 is conrmed to be a massive cluster at high redshift. Deep optical and near-infrared imaging show an overdensity of galaxies in both X-ray lobes, including a signicant excess of red galaxies (R K> 5:3) with colors typical of elliptical galaxies at z> 1. We have used new photometry to place better constraints on the redshifts of the cluster galaxies. A Keck NIRSPEC spectrum of one of the bright central galaxies in the eastern lobe shows a narrow H emission line at 1.485 microns, yielding a redshift of 1.263. The (O ii) 3727 A line from the gravitationally lensed arc is also detected, giving a redshift of 2.577 for the lensed galaxy and conrming prior measurements. The improbability of chance alignment and similarity of colors for the galaxies in the two X-ray lobes are consistent with the western lobe also being at z =1 :26. The system may thus represent a pair of clusters in the process of merging.

X-ray lobes of W50/SS433 system

The X-ray lobel lie on both sides (east and west) of SS433, and are presumably produced by the interaction of the jets of SS433 with the surrounding SNR W50. The non-thermal nature of the east lobe has been reported by Yamauchi et al. (1994) using the ASCA data. With the further ASCA observations, we studied the spectra and morphology of both the east and west lobes in detail. Their spectra have no emission lines, and are best described by power-law models with interstellar absorption. The X-ray emission becomes softer on the both sides with the distance from SS433. The surface brightness peaks closer to SS433 in the high-energy band than in the low energy band, suggesting that the high energy electrons in the X-ray lobes lose energies by synchrotron emission as they travel away from SS433. We estimate the magnetic field and the total energy of the high energy electrons to be a few μG and ∼ 10 46 erg respectively, where equipartition in energy between the relativistic electrons and magnetic field is assumed.

X-ray lobes of W 50/SS 433 system

The X-ray lobes lie on both sides (east and west) of SS 433, and are presumably produced by the interaction of the jets of SS 433 with the surrounding SNR W 50. The non-thermal nature of the east lobe has been reported by Yamauchi et al. (1994) using ASCA data. With the further ASCA observations, we studied the spectra and morphology of both the east and west lobes in detail. Their spectra have no emission lines, and are well described by power-law models with interstellar absorption. The X-ray emission becomes softer on both sides with increasing distance from SS 433. The X-ray surface brightness peaks closer to SS 433 in the high-energy band than in the low energy band, suggesting that the high energy electrons in the X-ray lobes lose energies by synchrotron emission as the travel away from SS 433. We estimate the magnetic field and the total energy of the high energy electrons to be ∼2 μG and ∼5 × 1046 erg, respectively.

ASCA results on SS 433: a galactic astrophysical jet system

The ASCA observations of SS 433 revealed two important properties of SS 433. The X-ray emission from the central point source exhibited multi-temperature thermal spectra which have two velocity components corresponding to the two anti-parallel jets outflowing at 0.26 c. The detailed analysis of the spectra revealed that the kinetic luminosity of SS 433 far exceeds the Eddington luminosity for any stellar size objects. The X-ray lobes, which are distributed at a very large scale (tens of parsecs) were found to have non-thermal spectra, suggesting presence of acceleration of energetic particles. There are still essential problems awaiting to be addressed. For example, identification of the compact object underlying the jets requires sensitive and detailed spectroscopy which will be made possible with ASTRO-E.

X-ray lobes of W 50/SS 433 system

X-ray lobes of W 50/SS 433 system

Rossi X‐Ray Timing ExplorerObservations of the Eastern Lobe of W50 Associated with SS 433

We present the Rossi X-Ray Timing Explorer (RXTE) observations of the SNR W50, associated with SS 433. The observations cover the X-ray lobe found between SS 433 and the outer eastern radio ear of W50. The X-ray spectrum measured with the proportional counter array and the High-Energy Timing Experiment in the 3-100 keV range favors nonthermal over thermal models for this part of W50. We combine the RXTE spectrum with the ROSAT and ASCA spectra, thus covering ~3 orders of magnitude in energy. The spectrum of the harder X-ray emission is well represented by a power law with a photon index of ~1.45 and a total X-ray luminosity of ~1.5×1035 ergs s-1 for a source distance of 5.5 kpc. We thus confirm the nonthermal nature of the inner X-ray lobe. We discuss its implications in the context of the interaction between the jets from SS 433 and the surroundings.

ROSATandASCAObservations of W50 Associated with the Peculiar Source SS 433

We report the observations of the X-ray lobes of the large Galactic source W50 associated with the two-sided jets source SS 433. The observations were made with the Position Sensitive Proportional Counter on board ROSAT. The eastern lobe has a knotty structure, with X-ray emission starting at ~15' from SS 433 and peaking at ~35'. Both thermal bremsstrahlung spectra with high temperatures (≥5 keV), as well as power-law spectra with flat photon index (Γ ~ 1-2), gave adequate fits. With ROSAT, we also detected an additional soft X-ray emission from the eastern lobe, at ~1° east of SS 433 and coincident with the radio ear. This region is associated with the terminal shock of the SS 433 jets. The western lobe has a similar morphology; however, the spectrum is softer, and no emission was found coincident with the western radio ear. We also report the observations of W50 with the Advanced Satellite for Cosmology and Astrophysics (ASCA), and combine the ROSAT and the ASCA data for a wide coverage of the spectra in the 0.1-10 keV energy range. We find that the spectrum from the brightest region (at ~35' from SS 433) requires an additional component to account for an excess of photons in the 1-3 keV band. The total X-ray luminosity from both lobes is ~1035-1036D25.5 ergs s-1. We discuss the origin of the X-rays in the model of emission from the supersonic jets of SS 433 interacting with the ambient medium, accelerating particles to very high energies, and producing a cocoon of hot shocked material. We present our interpretation in light of the correlation of X-ray emission with the map of W50 at other wavelengths.