X-Ray Emission from Extragalactic Jets

Abstract

This review focuses on the X-ray emission processes of extra-galactic jets on scales resolvable by the sub arcsec resolution of the Chandra X-ray Observatory. It is divided into 4 parts. The introductory chapter reviews the classical problems for jets, as well as those associated directly with the X-ray emission. Throughout this section, we deal with the dualisms of low powered radio sources versus high powered radio galaxies and quasars; synchrotron models versus inverse Compton models; and the distinction between the relativistic plasma responsible for the received radiation and the medium responsible for the transport of energy down the jet. The second part collects the observational and inferred parameters for the currently detected X-ray jets and attempts to put their relative sizes and luminosities in perspective. In part 3, we first give the relevant radio and optical jet characteristics, and then examine the details of the X-ray data and how they can be related to various jet attributes. The last section is devoted to a critique of the two non-thermal emission processes and to prospects for progress in our understanding of jets.

Optical Detection of the Pictor a Jet and Tidal Tail: Evidence Against an Ic/CMB Jet

“…Three emission mechanisms were plausible: synchrotron radiation from highenergy electrons moving in a magnetic field; synchrotron selfCompton emission, where synchrotron photons are scattered off of high-energy electrons (SSC); and inverse Compton scattering of electrons that boosts photons from the cosmic microwave background to very high energies (IC/CMB; Tavecchio et al 2000;Celotti et al 2001). For more details on various models for the physical systems underlying these emission mechanisms, see the review of Harris & Krawczynski (2006). In all models we assume that low frequency flux is provided by synchrotron emission; the label we attach to each model refers to the primary mode of X-ray emission, with radio and optical emission always produced by synchrotron emission.…”

“…While many FR II quasar jets have been detected in Hubble Space Telescope (HST) images, most are so distant that only a few point-like emission regions are found. Resolving structure in the knots is rare; one example of resolved structure is 3C 273, which has an unusually bright jet in the optical band and is close enough that HST resolves each knot (Marshall et al 2001;Harris et al 2006). The proximity of Pictor A and its FR II jet (located at a redshift of z = 0.035) makes it an appealing candidate for resolving small, dim features that are not detectable in more distant quasars.…”

Recent Progress in Understanding the Large Scale Jets of Powerful Quasars

“…Over the last 15 years, Chandra has detected X-ray emission from more than 100 jets (see [4,5] for reviews). These exciting observations have revealed that X-ray jets extend up to hundreds of kpc and are dominated by emission from bright jet knots and terminal hotspots.…”

Ruling Out Ic/CMB X-Rays in PKS 0637-752 and the Implications for Tev Emission From Large-Scale Quasar Jets

“…Over the past decade and a half since the launch of Chandra, dozens more kpc-scale quasar jets with anomalously hard and/ or high X-ray fluxes have been detected (e.g., Sambruna et al 2001Sambruna et al , 2002Siemiginowska et al 2003;Sambruna et al 2004;Marshall et al 2005;Harris & Krawczynski 2006;Siemiginowska et al 2007;Marshall et al 2011;Godfrey et al 2012a;Kharb et al 2012). The IC/CMB model has been by far the most popular explanation of these X-rays, though problems have been noted (e.g Hardcastle 2006; Harris & Krawczynski 2006). Besides the unconfirmed fast speeds required on the kpc scale, IC/CMB often requires the jet to be pointed very close along our line of sight (LOS), leading to a deprojected jet length longer than 1 Mpc, comparable to, or greater than the largest known giant radio galaxies .…”