Pulsars, transients and relativistic astrophysics

Abstract:

New Chandra observations of the giant (0.5 Mpc) radio galaxy 4C23.56 at z = 2.5 show X-rays in a linear structure aligned with its radio emission, but anti-correlated with the detailed radio structure. Consistent with the powerful, high-z giant radio galaxies we have studied previously, X-rays seem to be invariably found where the lobe plasma is oldest even where the radio emission has long since faded. The hotspot complexes seem to show structures resembling the double shock structure exhibited by the largest radio quasar 4C74.26, with the X-ray shock again being offset closer to the nucleus than the radio synchrotron shock. In the current paper, the offsets between these shocks are even larger at 35kpc. Unusually for a classical double (FRII) radio source, there is smooth low surface-brightness radio emission associated with the regions beyond the hotspots (further away from the nucleus than the hotspots themselves), which seems to be symmetric for the ends of both jets. We consider possible explanations for this phenomenon, and conclude that it arises from high-energy electrons, recently accelerated in the nearby radio hotspots that are leaking into a pre-existing weakly-magnetized plasma that are symmetric relic lobes fed from a previous episode of jet activity. This contrasts with other manifestations of previous epochs of jet ejection in various examples of classical double radio sources namely (1) double-double radio galaxies by e.g. Schoenmakers et al, (2) the double-double X-ray/radio galaxies by Laskar et al and (3) the presence of a relic X-ray counter-jet in the prototypical classical double radio galaxy, Cygnus A by Steenbrugge et al. The occurrence of multi-episodic jet activity in powerful radio galaxies and quasars indicates that they may have a longer lasting influence on the on-going structure formation processes in their environs than previously presumed.

Abstract:

We report the discovery of multi-scale X-ray jets from the accreting neutron star X-ray binary, Circinus X-1. The bipolar outflows show wide opening angles and are spatially coincident with the radio jets seen in new highresolution radio images of the region. The morphology of the emission regions suggests that the jets from Circinus X-1 are running into a terminal shock with the interstellar medium, as is seen in powerful radio galaxies. This and other observations indicate that the jets have a wide opening angle, suggesting that the jets are either not very well collimated or precessing. We interpret the spectra from the shocks as cooled synchrotron emission and derive a cooling age of ∼1600 yr. This allows us to constrain the jet power to be 3×1035 erg s-1 ≲ Pjet ≲ 2×1037 erg s-1, making this one of a few microquasars with a direct measurement of its jet power and the only known microquasar that exhibits stationary large-scale X-ray emission. © 2010. The American Astronomical Society. All rights reserved.

Abstract:

We present an analysis of observations of the doubly-lensed double hotspot in the giant radio galaxy J0816+5003 from MERLIN, MDM, WIYN, WHT, UKIRT and the VLA. The images of the two hotspot components span a factor of two in radius on one side of the lensing galaxy at impact parameters of less than 500pc. Hence we measure the slope of the lensing potential over a large range in radius, made possible by significant improvement in the accuracy of registration of the radio and optical frame and higher resolution imaging data than previously available. We also infer the lens and source redshifts to be 0.332 and > 1 respectively. Purely on the basis of lens modelling, and independently of stellar velocity dispersion measurements, we find the potential to be very close to isothermal.