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Beamed and Unbeamed X-ray Emission in FR1 Radio Galaxies
There is good evidence for X-ray emission associated with AGN jets which are relativistically boosted towards the observer. But to what jet radius does such X-ray emission persist? To attempt to answer this question one can look at radio galaxies; their cores are sufficiently X-ray faint that any unbeamed X-ray emission in the vicinity of the central engine must be obscured. The jets of such sources are at unfavourable angles for relativistic boosting, and so their relatively weak X-ray emission must be carefully separated from the plateau of resolved X-ray emission from a hot interstellar, intragroup, or intracluster medium on which they are expected to sit. This paper presents results arguing that jet X-ray emission is generally detected in radio galaxies, even those of low intrinsic power without hot spots. The levels of emission suggest an extrapolated radio to soft X-ray spectral index, alpha(sub tao x) of about 0.85 at parsec to perhaps kiloparsec distances from the cores.
Beamed and Unbeamed X-Ray Emission in FR1 Radio Galaxies
The research exploited ROSAT's sensitivity, together with its spatial and spectral resolution, to separate X-ray emission components in the sources. Prior to ROSAT, the dominant X-ray emission mechanism in radio galaxies as a class was unclear, with correlations between the X-ray and radio emission used on one hand to argue for a nuclear origin for the X-rays, and on the other hand for a thermal origin. Our observations (normally between 10 and 25 ks in length) routinely detected the target sources, and demonstrated that both resolved (thermal) and unresolved X-ray emission are typically present. Highlights of our work included two of the first detections of high-power radio galaxies at high redshift, 3C 280 and 3C 220.1. When combined with the work of two other groups, we find that of the 38 radio galaxies at z > 0.6 in the 3CRR sample, 12 were observed in ROSAT pointed observations and 9 were detected with the four most significant detections exhibiting source extent, including 3C 280 and 3C 220.1. Moreover, we discovered extended emission around five 3CRR quasars at redshift greater than about 0.4, one of which is at z > 0.6. Unification predicts that the X-ray environments of powerful radio galaxies and quasars should be similar, and our results show that powerful radio sources are finding some of the highest-redshift X-ray clusters known to date, pointing to deep gravitational potential wells early in the Universe.
Master Console, SMC
The Master Console oversees the function of Computer Systems in Firing room 1 (FR1). Master Console Operators, MCOs' for short, are our customer. I was integrated into the System Monitoring and Control (SMC) software team that is under the guidance of David Slaiman, who is the product group lead. I have been brought up to speed with System Monitoring and Control. The initial time spent reading SMC software design description and understanding how it works. The current Firing Room 1 Console Display is a floor layout giving the MCO two essential pieces of information which are Health and Status. When an issue arises, the MCO has to look on the display to find which console is affected and then the MCO must use the Reference designator from the display to manually search for the Portal Workstation (PWS) installed in the console using the hardware map; which is a long process to lookup a PWS if an issue is present. My project is to make the FR1 Console Display easier for the MCO's to pinpoint PWS's without having to lookup additional resources in the process. My project also includes updating Firing Room 1 Console Display to include the F1R Non-Redundant Set. The display does not have good use of space and functionality. PWS numbers were not present in the previous design and are the critical component in efficient understanding and administration of the consoles. Part of the process includes getting feedback from the customer, instead of just emailing them with a question, we made a proposal with changes so they could respond and give us their input; which proved to be an effective method for engaging them. In order to do this I had to use the Display Editor (DE) tool developed by NASA, Paint.Net and Visio. The process I have been using has been Visio to alter the floor layout of Firing Room and take advantage of the white areas, and then I take the altered floor plan into Paint.Net. Once in Paint.Net I put the new floor plan as a background to the standard console display. Paint.Net also serves as a tool to create the new service state bars for the new background; finally I used the DE to assemble everything and setup the right CUI's for each PWS.
Pair cascades in extragalactic jets. 1: Gamma rays
A model of the approximately 0.1-10 GeV gamma-ray jets observed by the EGRET instrument on the Compton Gamma Ray Observatory (CGRO) is developed. It is shown that the soft X-ray background in an active galactic nuclei (AGN) contributes an opacity to pair production and that a gamma-ray photosphere or 'gamma-sphere' can be defined whose radius increases with gamma-ray energy E(sub gamma). It is proposed that the observed gamma-ray emission is due to inverse Compton scattering of the ambient soft X-rays by relativistic pairs accelerated in situ by shock fronts in a relativistic jet. For a wide range of assumed physical conditions, the emission at a given E(sub gamma) originates from near the associated gamma-spheres; emission from below the gamma-sphere initiates a cascade down to the energy where the gamma-rays can escape freely. In this model, the slope of the emergent gamma-ray spectrum is determined by the scattered, soft X-ray spectrum and the variation of the particle acceleration rate with jet radius. In general it is expected that the variation in the gamma-ray flux will be either slower or later at higher energy. It is also shown that the efficiency of conversion of energy from injected high-energy pairs to 0.1-10 GeV gamma-rays is typically high so that the models are radiatively efficient. It is argued that the observed gamma-ray jets are likely to be particle-dominated, though magnetically confined. The gamma-ray spectrum should continue down to an energy approximately 5 MeV emitted from an annihilation radius within which the pair content of the jet is limited by annihilation. This is probably the site of the beamed hard X-ray emission. It is speculated that the relativistic jets associated with radio-loud AGNs are powered electromagnetically by a spinning black hole and that they are collimated by an encircling MHD wind leaving the accretion disk at a slower speed. Powerful FR2 radio sources are formed when the hole spins rapidly and the relativistic core accelerates the MHD sheath; low-power FR1 sources ensue when the opposite occurs. Finally, it is suggested that the key factor which determines whether or not a given active nucleus can form a jet and a radio to gamma-ray nonthermal continuum is the central density of mass-losing stars which, when large, precludes the formation of a super-Alfvenic, collimating wind.