Chandra Observations of 3C Radio Sources with z<0.3: Nuclei, Diffuse Emission, Jets and Hotspots

VERSION 2009 JAN 25: FM Preprint typeset using LATEX style emulateapj v. 11/10/09 CHANDRA OBSERVATIONS OF 3C RADIO SOURCES WITH Z<0.3: NUCLEI, DIFFUSE EMISSION, JETS AND HOTSPOTS F. MASSARO1, D. E. HARRIS1 G. R. TREMBLAY2 D. AXON2,11, S. A. BAUM3, A. CAPETTI4, M. CHIABERGE5,7, R. GILLI6, G. GIOVANNINI7,10, P. GRANDI8, F. D. MACCHETTO5, C. P. O’DEA2, G. RISALITI9, W. SPARKS5 version 2009 Jan 25: fm ABSTRACT We report on our Chandra Cycle 9 program to observe half of the 60 (unobserved by Chandra) 3C radio sources at z<0.3 for 8 ksec each. Here we give the basic data: the X-ray intensity of the nuclei and any features associated with radio structures such as hot spots and knots in jets. We have measured fluxes in soft, medium and hard bands and are thus able to isolate sources with significant intrinsic column density. For the stronger nuclei, we have applied the standard spectral analysis which provides the best fit values of X-ray spectral index and column density. We find evidence for intrinsic absorption exceeding a column density of 1022 cm−2 for one third of our sources. Subject headings: galaxies: active — X-rays: general — radio continuum: galaxies 1. INTRODUCTION Extended radio galaxies are classified into two main types (Fanaroff and Riley 1974; Miley 1980; Bridle 1984). The more powerful sources (FRII) tend to have an edge-brightened radio structure dominated by compact bright hot spots. These sources often show either no or one jet which may be rela- tivistic along its entire length (Laing 1988; Garrington et al. 1988). The lower luminosity sources (FRI) tend to have edge- darkened structures which resemble “plumes” and usually ex- hibit two jets. The jets in FRIs may initially be launched rel- ativistically but seem to decelerate on subkpc scales likely through interaction with the environment (e.g., Laing et al. 2008). There are intrinsic differences in the central AGN of these two types of sources (e.g., Baum, Zirbel, O’Dea 1995; Evans et al. 2006, Hardcastle et al. 2009a). Most Narrow Line FRIIs and a few FRIs show evidence for a hidden quasar continuum source and Broad Line Region (BLR) (e.g., Co- hen et al. 1999; Tadhunter et al. 2007). The sources with the hidden quasar also produce optical emission line nebulae with high ionization lines (High Excitation Galaxies, HEGs) while those without the hidden quasar produce only low ionization lines (Low Excitation Galaxies, LEGs) (e.g., Hine and Lon- gair 1979, Laing et al. 1994, Rector and Stocke 2001). There 1 Harvard, Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 2 Dept of Physics, Rochester Institute of Technology, Carlson Center for Imaging Science 76-3144, 84 Lomb Memorial Dr., Rochester, NY 14623 3 Carlson Center for Imaging Science 76-3144, 84 Lomb Memorial Dr., Rochester, NY 14623 4 INAF - Osservatorio Astronomico di Torino, Strada Osservatorio 20, I-10025 Pino Torinese, Italy 5 Space Telescope Science Institute, 3700 San Martine Drive, Balti- more, MD 21218 6 INAF - Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127, Bologna, Italy 7 INAF - Istituto di Radioastronomia di Bologna, via Gobetti 101 40129 Bologna, Italy 8 INAF-IASF - Istituto di Astrofisica Spaziale e fisica cosmica di Bologna, Via P. Gobetti 101, 40129, Bologna, Italy 9 INAF - Osservatorio Astronomico di Arcetri, Largo E. Fermi 5, 50125, Firenze, Italy 10 Dipartimento di Astronomia, Universita’ di Bologna, via Ranzani 1, 40127 Bologna, Italy 11 School of Mathematical & Physical Sciences, University of Sussex, Falmer, Brighton, BN2 9BH, UK are also radio sources with properties intermediate between the FRIs and FRIIs, e.g., the “Fat Doubles” (Owen and Laing 1989). The two main unsolved issues concern the origin of the FR I / FR II dichotomy (how it is related to different accel- eration and emission processes), and the nature of the differ- ent emission line regions between LEGs and HEGs (see Chi- aberge et al. 2002 and Hardcastle et al. 2007). The morphological features of extragalactic radio sources can be described naturally with a small number of compo- nents: core, jets, hotspots and lobes. While their radio to opti- cal emission is typically described in terms of synchrotron ra- diation by relativistic particles, the origin of X-ray emission in extended structures (jets and hotspots) is still unclear, but cer- tainly non-thermal (Harris & Krawczynski 2002). The main open question lies in which mechanism, synchrotron or in- verse Compton (IC) scattering, dominates the X-ray emission. The former describes emission from low power jets (Harris & Krawczynski 2006), while the latter provides a good expla- nation for high power radio galaxy and quasar jets, in which the seed photons for the IC scattering could be the Cosmic Microwave Background (CMB) (Tavecchio et al. 2000). Only by combining X-ray observations with historical and/or simultaneuos data in other wavebands, is possible to build up the Spectral Energy Distribution (SED) of cores, je

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