Multiwavelength study of Cygnus A

Steenbrugge, K. C.; Blundell, Katherine M.; Pyrzas, S.

doi:10.1051/0004-6361/201322339

Cited by 5 publications

(4 citation statements)

References 22 publications

(45 reference statements)

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“…We therefore estimate a total AGN speed of ≃ 270 km s −1 with respect to the gas, with a total systematic uncertainty of a factor of ∼ 2. Our projected speed is consistent with the proper motion estimates from Steenbrugge et al (2014).…”

Section: Rim Pressuresupporting

confidence: 85%

The Cocoon Shocks of Cygnus A: Pressures and Their Implications for the Jets and Lobes

Snios

Nulsen

Wise

et al. 2018

ApJ

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACT We use 2.0 Msec of Chandra observations to investigate the cocoon shocks of Cygnus A and some implications for its lobes and jet. Measured shock Mach numbers vary in the range 1.18-1.66 around the cocoon. We estimate a total outburst energy of ≃ 4.7 × 10 60 erg, with an age of ≃ 2 × 10 7 yr. The average postshock pressure is found to be 8.6 ± 0.3 × 10 −10 erg cm −3 , which agrees with the average pressure of the thin rim of compressed gas between the radio lobes and shocks, as determined from X-ray spectra. However, average rim pressures are found to be lower in the western lobe than in the eastern lobe by ≃ 20%. Pressure estimates for hotspots A and D from synchrotron self-Compton models imply that each jet exerts a ram pressure 3 times its static pressure, consistent with the positions of the hotspots moving about on the cocoon shock over time. A steady, one-dimensional flow model is used to estimate jet properties, finding mildly relativistic flow speeds within the allowed parameter range. Models in which the jet carries a negligible flux of rest mass are consistent with with the observed properties of the jets and hotspots. This favors the jets being light, implying that the kinetic power and momentum flux are carried primarily by the internal energy of the jet plasma rather than by its rest mass.

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Section: Rim Pressuresupporting

confidence: 85%

The Cocoon Shocks of Cygnus A: Pressures and Their Implications for the Jets and Lobes

Snios

Nulsen

Wise

et al. 2018

ApJ

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“…From previous work, we know that the jets are precessing and that the jet speed is less than 0.5c, a relatively low value (Steenbrugge et al 2010). We also know that Cygnus A is moving through the cluster, with a radial velocity offset of at least 163 km s −1 (Ledlow et al 2005) and a similar order of magnitude proper motion (Steenbrugge et al 2014). Hence, the direction of the jet certainly changes over time in this source.…”

Section: Introductionmentioning

confidence: 86%

Multiwavelength study of Cygnus A

Pyrzas

Steenbrugge

Blundell

2015

A&A

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Context. The jets in Faranoff-Riley type II AGN are supposed come to an abrupt halt in hotspots on opposite sides of the nucleus. Quite commonly, two hotspots are observed in each lobe. The origin of the second hotspot is currently poorly understood. Aims. Our aims are to determine the origin of the secondary hotspot in the western lobe of Cygnus A from high resolution multifrequency radio images; to determine the minimum Lorentz factor of the electrons in the hotspots, often referred to as the low-energy turnover; and to study the magnetic field configuration of the hotspots. Methods. We used 151 MHz Merlin and 327 MHz, 1.4, 5, 8, 15, and 43 GHz VLA images to determine the centroid of the peak luminosity, the spectral shape, and polarization fraction of both hotspots in the western lobe of Cygnus A. Results. We find a spatial shift in peak luminosity between the lower and higher frequency images for both hotspots. We determine the minimum Lorentz factor of the electrons to be ∼1000, and show that most of the emission from the primary hotspot is linearly polarized. The minimum energy magnetic field strength is found to range between ∼0.14 and ∼0.5 mG in both the primary and secondary hotspots. Conclusions. From the low polarization and the determined outflow velocity, we conclude that the secondary hotspot is no longer a strong shock, and is an expanding, and hence a fading hotspot. This hotspot has an age that is of the same order of magnitude as the jet precession period.

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“…The two classes seem to overlap at P tot /L cool ∼ 50-60, where we find that NGC 5813, a low-luminosity FR I radio galaxy, has a larger ratio than Cygnus A, the archetypal FR II radio galaxy. However, the different environments have to be taken into consideration; NGC 5813 is a galaxy group (Randall et al 2011), while Cygnus A is at the center of a galaxy cluster (e.g., Steenbrugge et al 2014). In this context, previous studies noted that the relative ratio of X-ray cavity heating power to cooling luminosity appears to be five times higher in low-mass systems than in rich clusters (e.g., Gitti et al 2012).…”

Section: Shock and Cavity Heating Of Hot Atmospheresmentioning

confidence: 99%

Multiple Shock Fronts in RBS 797: The Chandra Window on Shock Heating in Galaxy Clusters

Ubertosi

Gitti

Brighenti

et al. 2023

ApJ

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Using ∼427 ks of Chandra observations, we present a study of shock heating and intracluster medium (ICM) cooling in the galaxy cluster RBS 797. We discover three nested pairs of weak shocks at roughly 50, 80, and 130 kpc from the center. The total energy associated with the shocks is ∼6 × 1061 erg, with the central active galactic nucleus (AGN) driving a pair of weak shocks every 20–30 Myr with a power P sh ≈ 1046 erg s−1. Based on its morphology and age (∼30 Myr), the inner cocoon shock is associated with the four equidistant X-ray cavities previously discovered. From the thermodynamic analysis of the inner 30 kpc, we find evidence for ICM condensation into colder gas between and behind the X-ray cavities. The total AGN mechanical power (cavities and shocks) of 3.4 × 1046 erg s−1 can balance the ICM radiative losses, estimated as L cool = 2.3 × 1045 erg s−1. By building plots of P cav versus L cool, P shock versus L cool, and P tot versus L cool for RBS 797 and 14 other galaxy clusters, galaxy groups, and elliptical galaxies where both cavities and shocks are detected, we verify that the most powerful outbursts are found in the strongest cooling systems. Ultimately, we observe that the mechanical power of the AGN exceeds the gas radiative losses by a factor that is different for FR I and FR II radio galaxies, being less than a few tens for FR Is (as RBS 797) and more than roughly 100 for FR IIs.

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Multiwavelength study of Cygnus A

Cited by 5 publications

References 22 publications

The Cocoon Shocks of Cygnus A: Pressures and Their Implications for the Jets and Lobes

The Cocoon Shocks of Cygnus A: Pressures and Their Implications for the Jets and Lobes

Multiwavelength study of Cygnus A

Multiple Shock Fronts in RBS 797: The Chandra Window on Shock Heating in Galaxy Clusters

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